How much energy will my solar cells produce?

Average daily production for solar PV cells in Australia

by Solar Choice Staff on January 19, 2010

in Installation advice,Inverters,What are the right solar PV cells for you?

The electrical energy output of solar cells is obviously one of the crucial things that you need to know when looking to install a solar system. Some solar energy companies are giving a wide variety of unreferenced numbers, so we have done our research and provide you with fully referenced and reliable information for you to consider.

What is energy output?

The power rating of your system (kilowatts, or kW) is a measure of how big your generation system is, not how much it will produce. This is analogous to a car engine, where the size of the engine gives you an indication of how powerful it is, but does not itself tell you how much petrol it will use, although the two are related.

If your state has a Solar Feed-in Tariff and you have a solar power system, you can be paid for the amount of electrical energy (kilowatt-hours or kWh) your solar system produces. Hence, that is what you need to know when doing the sums on how much revenue you can expect from your installation.

What is the energy output dependent on?

Of course the first factor influencing how much electrical energy you will generate is the size (otherwise known as rated power) of your solar installation. A large installation (higher kW’s) will produce more electrical energy (just as a bigger car engine has more grunt).

But if we move past the obvious impact of size, the amount of energy your solar cells produce depends on how much fuel they are fed (just as the amount of energy a car engine will produce depends on how much petrol you pump into it via your foot on the throttle). In the case of solar PV cells, their fuel is the sun.

The amount of sun your solar cells are exposed to (and hence how much energy they will generate) depends upon:

  • The orientation and tilt of your installation (which will be optimised by your installer)
  • Whether there are shadows cast over your cells (due to trees, buildings etc)
  • The number of daylight hours (governed by where you live)
  • The intensity of the sunlight (governed by where you live)
  • The number of hours of full sun vs cloudy days (governed by where you live)

If we exclude the first two factors, which you have a degree of control over, your location in Australia is the primary variable dictating how much energy your cells will produce. Hence, a 1.5kW system in Melbourne will typically not produce as much electrical energy over the year as the same system in Alice Springs.

The figures for average daily production

Fortunately, studies have been conducted that take all of the above factors into account and give the average energy output for solar cells in locations around Australia. These figures are given as:

The amount of electrical energy (kWh) a 1kW grid connected solar PV system will generate on an average day (kWh/kWp.day).

The most comprehensive source of this information is the Clean Energy Council (the body that the Australian Government charges with accrediting solar cells, inverters and installers):

Average-Daily-Production-of-Renewable-Energy

Average daily production of solar PV cells in Australia
p4, “Electricity from the sun: Solar PV systems explained” by the Clean Energy Council

Researching this topic will reveal other credible sources, with slightly different figures. For instance:

Although these figures are in the same vicinity the variance demonstrates the fact that it’s not quite possible to put an exact unequivocal figure on the energy you will produce from you solar cells. Indeed, as Dr Anna Bruce, Lecturer at the School of Photovoltaic and Renewable Energy Engineering at The University of New South Wales informed us, different solar systems both rated at 1kW sitting side by side may produce different amounts of energy due to the quality and efficiency of their components, how the grid is functioning and how well your system deals with high temperatures. Her expert advice is that “4kWh/kWp.day in Sydney is certainly feasible if a system has optimal tilt and orientation and is running well”.

So the Clean Energy Council figures above act as a good guide and are one of the best and most comprehensive sources available, however due to the nature of solar, your system may produce more, or a little less than the figures given.

Kobad Bhavnagri
Solar Energy Consultant

© 2010 Solar Choice Pty Ltd

{ 161 comments… read them below or add one }

Mark December 16, 2011 at 8:46 pm

Hi again id like to know what the best combination of panels and strings,i have a growatt 4.2kw inverter which has one string of ten 190 watt panels connected and i have another ten sitting here waiting to be hooked up,the inverter has 4 inputs so i gather thats for 4 strings of panels but im confused as my installer tells me 10 per string is good anyhow id love some input on this matter regards mark.

Reply

admin December 19, 2011 at 11:44 am

Hi Mark,

Unless you have shading issues, whether you decide to go with 4 or 2 strings of panels shouldn’t make a difference. I’ve done a bit of research and the max DC input voltage of a Growatt4200ML inverter (I assume this is yours) is 600V, and an MPPT range of 120V-550V. What is the voltage output for the panels that you have?

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Mike January 2, 2012 at 12:50 pm

A very interesting site, which also demonstrates there are quite a
number of posters that have a good knowledge of solar power.

Perhaps a member can answer the following question for me!.

We are a retired couple residing in Rockingham, Western Australia, my wife is totally disabled and suffers among other with things a
condition known as “Thermoregulatory Disfunction” and has no
capacity to control body temperature when exposed to extremes
of weather conditions.

Subsequently our electricity bills (every 60 days) is now around
$500 (an average of 41 units per day), with more increases on the
unit rate guaranteed to be implemented in the near future, so our
premier (Barnett) has warned.

Can anyone give me a clue as to the cost of a system that would
provide a break even situation for us so that we can recover the cost over a period of years.

Reply

admin January 10, 2012 at 2:43 pm

Hi Mike,

Thanks for your inquiry.

Your area receives an annual average of 6 peak sun hours per day–i.e. if you have a 1.0kW system, you could expect it to produce about 6kWh (“units”) of electricity per day. Since you require 41 units per day, roughly speaking a 7kW system is probably what you’re looking for. At current prices, this could run you anywhere between 18 and 22 thousand dollars.

Keep in mind, however, that you will only stand to benefit from a system of this size if you wisely time your usage to coincide with generation–since the cancelation of the state’s feed-in tariff, in your area of WA the only ‘renewable energy buyback scheme’ available is through Synergy and is a nominal 7c/kWh. This means that you will only be paid 7c for every unit that you feed into the grid, so it makes more financial sense for you to use the power directly instead.

Sizing a system to make it worth your while would require a bit of analysis regarding when your demand is highest (e.g. evenings? daytime? around the clock?) for each season. It might even be worth your while to invest in energy storage in the form of batteries.

Our automatic quote comparisons do not include prices for 7kW systems, but our brokers can tailor a quote comparison that suits your needs. To initiate a dialogue, either fill out the form on the right, or email sales@solarchoice.net.au. Our services are free and impartial.

Reply

Mark January 14, 2012 at 9:41 pm

Hi thanks for the reply, i have no shading issues the voltage output is vmp 36.6 voc 44.7 imp 5.19 amp ,and yes i think it is a growatt 4200 mtl kind regards mark

Reply

admin January 16, 2012 at 1:28 pm

Hi Mark,

The specs of the inverter and panels, plus the fact that you don’t have shading issues, indicate that 2 strings of 5x panels on the second (currently unused side) of the MPPT input would be ideal. 2 strings of 5x is preferable to 1 string of 10x just on the odd chance that something goes wrong with the panels–with conventional strings of panels as we are discussing here, the malfunction of just 1 panels can knock out the entire string. So it’s best to hedge your bets.

Simple analysis and calculations with regard to your query can be found below.

Growatt 4.2 Inverter
-MPPT input voltage range: 120V-550V
-MPPT input current range: 15A

Your panels (those not yet connected, assuming they are all fed into only one side of the MPPT input):

Single string configuration–
36.6V * 10 = 366V
5.9A * 1 = 5.9A

Double string configuration–
36.5V * 5 = 183V
5.9A * 2 = 11.8A

As you can see, both configurations are well within the acceptable ranges on both counts. However, as mentioned above, all things being equal, it’s best to hedge your bets with more strings of fewer panels.

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Mrs Pauline Leatham March 16, 2012 at 7:30 am

Good morning,could you please help us with some advice.We have a solar system 3kw with a german converter. We have just received our first electricity bill for 91 days, we are extremly upset as in all that time we have just made 222 kws and it reduced our bill for $97.68 only. We live here in sunny qld and for such a big outlay our bills are still over $500. We thought having 16 panels would have lowered the bill. Thank you any help would be appreciated.

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admin March 19, 2012 at 12:12 pm

Hi Pauline,

How much were your bills prior to installing your system? And have you contacted your installer to let them know that your system is not meeting your expectations? And do you have a monitoring device to track your system’s daily output?

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Damien April 17, 2012 at 1:15 pm

This message is for Mike from Rockingham above with the disabled wife.

He may not be aware of this rebate: http://www.finance.wa.gov.au/cms/content.aspx?id=1691

Which is provided by the state government called the Thermoregulatory Dysfunction Energy Subsidy Scheme

Reply

hayley lehman May 16, 2012 at 7:11 pm

Hi there,
I’m a business student doing a project for uni. If you have a 3KW system and for sydeny they have on average 8 hours of sunlight a day then the system if perfect conditions working at full capacity should produce 3 times 8 = 24kw/h a day so is the average system in darwin working at 11.7/24 = 48% ?

Reply

admin May 17, 2012 at 11:09 am

Hi Hayley. Sunshine hours are not the same as ‘peak sun hours’, an industry term referring to the equivalent of all the solar irradiation ‘concentrated’ into uniform units. In the morning and evening, the sunshine is more diffuse on any given roof or solar panel; around midday it is highly concentrated. In reality, Sydney only gets about 4 (actually more like 3.6) peak sun hours per day, averaged throughout the year (more in summer, less in winter).

So a 3kW system in Sydney would produce more along the lines of <12 kWh per day. Since Darwin gets about 4.6 daily peak sun hours averaged over the year, you’re looking at about 13.8kWh there.

When you talk about efficiency, it’s important to distinguish between panel efficiency (or conversion efficiency), cell efficiency, and system efficiency. Your figure of 48% efficiency based on 24 hours doesn’t make any sense in the context of solar power, unless you’re comparing to other forms of power generation.

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Troy May 20, 2012 at 11:29 am

Hi I was wondering if u could tell me, How do I know that all my panels are working to is potential or is working at all.
Ive got a Samil Power 3.3kw inverter with 12 Sun earth 250v panels.
How can I check this on my inverter or wherever.
Sorry for the stupid question, but I am quite ignorant to the facts of Solar power and its workings.
Thanks for ur information

Reply

admin May 28, 2012 at 2:59 pm

Hi Troy,

Not an ignorant question at all, but a perfectly reasonable one.

The fact is that unless you have micro-inverters (i.e. inverters on each panel–such as Enecsys or SolarEdge), most systems do not have the capacity to track the performance of individual solar modules. Inverters with dual inputs and multiple power point tracking (MPPT) capacity can, however, track the performance of ‘strings’ of panels. Do you know how many strings your panel array is divided into?

You can see the stats for Samil Power 3.3kW inverters on the Samil Power website.

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Pranesh PAL May 28, 2012 at 3:27 pm

Hi – My Daily consumption is 23.25kWhr. I have had a quote of a 5kW unit for $15.5k. What would be the expected rate of return on this investment (Brisbane based). AGL have a tariff of 52c (till 2018). What is the industy average of Daytime Vs Night time usage. Is 40%:60% a nominal value that is used in calculations? It would be nice if I could get a proper breakdown on this. Is there a meter that can record and store sunlight duration and night time power consumption? This will get a better idea of available export.
My calcs show a payback of 10+ years ( I have west mount on the roof so derated values apply). Is my calc in the ball park? Looks like it is better to keep the money in the home loan. Obviously I have not included tariff increases in my calcs. Your feedback please.

Reply

admin May 30, 2012 at 11:14 am

Hi Pranesh,

Thanks for the comment. I’ve addressed your queries below.

1) A 5kW system for $15.5k is not an unreasonable price if it includes all high-end product. What are the brands of the panels and inverter that the quoted system will be using? At the moment, it is not unusual to find systems at around $2/watt–An ok quality 5kW system can be purchased for around $10k right now.

2) As the Queensland Solar Bonus Feed-in Tariff Scheme offers a rate that is higher than the retail electricity tariff, you are actually better off trying to export as much of your solar power to the grid as possible because it is worth more when you do so. (If you were in a state with a feed-in tariff incentive that is lower than the cost of retail electricity such as NSW, it would make more sense for you to try to self-consume as much of your solar power as possible, as this would save you more money than exporting. Read more–> The economics of a 1:1 Solar buyback vs Solar Feed-in Tariffs.)

3) I’ve just used the Brisbane Solar System Payback Calculator (at the bottom of that article) to calculate a rough payback period, and although the figures therein are only rudimentary, with a feed-in tariff rate of $0.53 you can expect the system to pay itself off within about 5 years, even with a $15k system. How did you arrive at your conclusion that it would be 10? The payback period would only be that long if you were in a state without a significant feed-in reward and if you did not closely monitor and manage the timing of your electricity use.

4) Most ‘Smart Meters’ will tell you when you are consuming and exporting your electricity, but to date none of them are explicitly linked with the rising and setting of the sun–or if they do exist, they are not widely commercially available. This is a good thing to watch out for, though. You could consider the PowerRouter, but it is arguable whether the extra cost is worth the difference in payback time for the average household.

Advice and solar quote comparisons through Solar Choice are 100% free to our customers, so feel free to fill out the form to the right of the page or give us a ring on 1300 78 72 73 to initiate a dialogue with one of our brokers. We look forward to hearing from you, and hope this response was helpful!

Brisbane Solar Power ROI calculator

Reply

D haye June 12, 2012 at 7:52 am

Hi
I am in Melbourne and have A 4Kw system comprising an Eversol T4600 inverter and 16 XH (Chinese) solar panels. The panels face west on a roof of 30 degrees. The system has never produced more than 2700w. I have had it checked by the installer and an idependent check and have been told there is nothing wrong with the installation but no one can tell me why the system is 40% down. My roof pitch is 23%. The system has produced an average of 7.2Kwh/day since installed. Do you have any ideas?

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admin July 9, 2012 at 4:08 pm

Hello D,

Thanks for the comment.

There are a number of factors that could potentially be affecting the performance of your system.

First of all, in order to understand what sort of output you should be expecting, it would be helpful to know what the total rated capacity of your solar panel array is–there are different models of XH solar panels, each with a different capacity. I assume they are approximately 190W, as this is a common capacity for residential solar panels. If they are indeed 190W panels, your array capacity will sit at around 3.04kW. This would be about 1.5kW lower than the capacity of your inverter. I cannot find the efficiency curve for the Eversol T4600, but it may be the case that it is being underpowered, which could result in a disproportionate loss of efficiency. (Read more about inverter efficiency.)

Another problem could be the fact that your panels are west-facing. The ideal scenario is to have your panels facing due north, but it is not uncommon to put panels on an eastern or western roof if a north-facing roof does not exist. If all else is perfectly arranged, a solar system with panels on a tilted roof facing due east or due west will suffer an approximate 20% loss off output. Assuming that your inverter is underpowered, however, the output could be even more severely compromised by the western aspect of the roof/panels.

Another issue could be a fault with the panels. XH are not a tier-1 manufacturer of solar panels. If there is a fault with even 1 of your panels (i.e. a cracked cell), the output of the entire array or of that ‘string’ could be compromised. (Similar to the effect that shading has on panels.) It wouldn’t be possible to check this without testing each panel, however (although you could narrow it down if your array has more 2 strings within it by checking to see if one of them is not producing as it should be). If it is a problem with one or more of the panels, you’ll have to check into the warranty. If XH does not have an office in Australia and you do find a problem with one of the panels, you may have to send it back to China for servicing, or it may take some time for them to get you a new one.

Alternatively, you can get in touch with the company that installed your system–if it was less than 5 years ago, you will likely have a warranty that is still valid with them.

There could be other reasons your system is not performing as it should, but these are likely culprits for the unexpectedly low yields of your system. Best of luck with it, and hope you found this helpful.

Reply

D haye July 14, 2012 at 6:58 am

Thank you for your comments.
My system comprises 16 x 250w panels facing west on a 23 degree roof with no shading. The system comprises 2 strings of 8. Both strings and all panels have been tested and I have been told the voltage in panels and strings are within spec.
My brother also located in Melbourne has the exact same system. His NORTH facing system continually produces 80-100% kw/h per day greater than mine. I have had the inverter replaced with one of the same type, but it made no difference. Any ideas would be very welcome as no one appears to be able to explain why my production is so poor (average over the last 5 months = 7.5kwh/day)

Reply

admin July 26, 2012 at 6:18 pm

Hi D,

The difference in orientation would explain the bulk of the difference between your system’s performance and that of your brother’s system. You should be looking at about 10kWh per day on average throughout the year with that setup (you can knock about 20% off the efficiency with west-facing solar arrays vs north-facing ones). In the winter this number will be lower and in the summer higher.

Your numbers are not too far off from what you should be expecting, especially if you’re quoting numbers from the winter months.

Just a couple of questions: Is your inverter properly sized to suit your panel array? Also, what is the tilt angle of your brother’s array?

Reply

D haye August 7, 2012 at 8:21 am

Thanks for the comments. I am still at a loss to understand how my brothers same system, facing north on a roof pitch of 25 degrees can provide 100% more kwh/day than mine. If I am losing 20% efficiency (I have been told by various people that a west facing system can lose between 5% and 20% (depends who you talk to) how can his produce 100% more, It doesn’t add up. The eversol T4600 is rated at 4600w (specs can be found at ever-sol.com.au then products then inverters then eversolTL then TL4600). and I have 16 x 250w XH solar panels ( found at solar360.com.au). It just doesn’t seem right that his prodution is so much greater than mine. I don’t understand your comment regarding my system is performing to expectations. If this is so, my brother would have to have a far superior system but that is not the case. Any assisstance would be greatly appreciated

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admin August 7, 2012 at 11:31 am

Hi D,

Thanks for coming back.

I retract my earlier statement that your system is not performing very far below what it should be, but whatever the problem is, it is not likely due to the tilt angle or orientation of your roof. Sorry about the confusion.

I know you said you had someone check out the system, but have you had the individual panels tested? The Evasol TL4600 has 2 DC inputs and one MPPT. One of the 2 strings could be dragging down the output of your system, potentially due to a flaw in one of the panels.

Des June 23, 2012 at 9:09 am

Hi Everyone,

does anyone have a free program to record your daily grid power usage, solar system output, etc and then using these figure calculate what your power bill will be?? Also want it to record all solar output and be able to produce graphs, tables, etc.
I live in Cairns

Des

Reply

admin July 4, 2012 at 4:57 pm

There are companies out there that have monitoring solutions like those you’ve described, but ordinarily such systems don’t come standard with systems. They probably should be, as people are much more likely to watch and change their usage patterns if they know their system production and power consumption statistics in real time.

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Shoun jahromi June 27, 2012 at 11:06 pm

Hi, wie are Interested to get a 2kw System to Cover our aircondition use. If we are producing energy during the day and don’t use it we sell it to the government and at night when we are home we buy it back for the current price of electricity? We were under the impression that you use your own production up first for free and then buy as required.

Thank you clarifying this for us.

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admin June 29, 2012 at 5:30 pm

Hi Shoun,

Thanks for the comment. You’re under the right impression: At present most inverters will automatically direct the solar power your system produces to your home appliances (if you have any running), and direct any surplus into the grid. If you are in a state with a Solar Feed-in Tariff, however, then electricity retailers are required to purchase your power at a premium rate. If there is no Feed-in Tariff on offer where you are, they may not have to pay you anything, or possibly only very little.

Read more: The economics of a 1-for-1 Solar Buyback scheme vs a Solar Feed-in Tariff

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Chris Gillett June 28, 2012 at 1:48 pm

Hi, I live in a house where the ridge runs almost north/south. If I get a 3kw system can I put half the panels facing east and the other half west? Will this mean that only half will produce power in the morning and the other half in the afternoon as 1 half will be facing away from the sun? If this can be done will it be more efficient splitting the panels or having them all on the side that faces slightly more north?

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admin June 29, 2012 at 5:24 pm

Hi Chris.

Thanks for the comment. I can’t really answer your question until I have a bit more information from you.

1) Which state are you in? (Some states have feed-in tariffs, some don’t.)

2) Are you eligible for any feed-in tariff? (If you are, it would probably be safe to split the array. If not, it’s not advisable unless you’re home.)

3) Is there any shading on either side of your roof? (If there is you won’t want to install panels on that side.)

4) Is there anyone home during the day? (If someone is home during the day using power, it make sense to split the array. If you expect to use more power only in the afternoon, you should aim to have most of the panels on the west-facing roof.)

In the meantime, you might also want to read this article: East vs west orientation for solar panels

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Ann July 1, 2012 at 9:08 pm

Hi I hope that you can help me I bit confused on how many solar panels I really need I’m in Perth WA I’ve been told that I need 38x190w with 2.2.5kw inverter it seems such a lot of panels although they cannot promise that it would cover 100% of my electricity. my bills range from $321.80 for 58days with 1472 total units (oct to Dec.) and $571 for 63days with 2614 total units (dec to feb) then I had an estimated bill of $738.20 for 63days (feb to apr) with 3376 total units and the bill after that was for $92.95 with 425 total units. Thank You.

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admin July 4, 2012 at 2:54 pm

Hi Ann,

Thanks for the enquiry.

In most cases in Western Australia, where the Solar Buyback rate currently sits at only 3c/kWh, no solar system will completely offset a power bill. The most you can hope for is a big chunk to be taken out by avoiding the purchase of electricity from the grid–you can only do this during the daytime, as this is the only time your system will be producing power.

A bit more concerning, however, is that your inverter capacity and total solar panel capacity don’t seem to match up. Perhaps you typed the number of panels incorrectly? 38x190W panels would be 7.22kW of panels with only a 2.5kW inverter? Are these figures correct? It’s not possible to work out the rest of the figures without first getting these straight.

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Ann July 4, 2012 at 5:54 pm

What I’ve been told is that 2 x 2.5kw ( which is 5kw) inverter with 38 x 190w panels. I hope this does help. Because I’d hate to spend all this money with so many panels and still have to pay an electricity bill.

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admin July 26, 2012 at 7:43 pm

Hi Ann,

38 x 190W panels would be overkill for 2 x 2.5kW inverters, as it’s more than 7kW worth of panels and your system output will basically be capped by the capacity of the inverter. I’m also wondering why they’re suggesting 2 x 2.5kW inverters as opposed to a 5kW or 7kW inverter. I don’t mean to disparage, but it doesn’t sound like a trustworthy operation.

Let’s also be clear that having solar panels will ever completely eliminate your power bill. There is currently no Feed-in Tariff in WA, so you do not get any credit on your bill for power that you export to the grid (well, actually you can get about 8c/kWh, but this is not much). You can offset your power bills by consuming your own solar power as it is being produced, but when night falls and you want to turn the lights or oven on you’ll have to draw it off the grid, which means paying for it.

The thing you need to do is 1) figure out how much electricity you can reduce in your household and 2) how of your electricity-using activity you can shift to daytime hours, when you’ll be able to take advantage of your power-producing solar panels. Only then will you be able to figure out what size system you need. As a rough estimate, however, the average household in a state with no feed-in tariff would benefit most from 3kW, 4kW, or 5kW solar systems.

If you’re still looking, give us a ring or fill out the form to the right of this page to get a free and instant solar quote comparison of installers who service Perth. Our service is free and impartial and we do our due diligence to ensure the installer in our network are reputable and do a quality job.

Best of luck!

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Lois July 7, 2012 at 9:20 pm

Hi,
I have a quote for a 3kW system with a 5kW inverter, reading the many comments from others I am wondering if the 5kW inverter is an overkill?

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admin July 9, 2012 at 5:58 pm

Hi Lois,

Oversized inverters can result in inefficiencies in your system’s output and are not recommended unless you plan on adding the balance of panels to match up with the inverter capacity within 6 months after the initial installation. Read more about inverter efficiency.

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Geoff July 18, 2012 at 1:15 pm

Hi,
Is there an expert body or person from who I can get an impartial opinion as to if some individual cells in a panel are cracked. I can see physical random cracks through several individual cells but the supply company says this is a cosmetic non issue and that the system total output as recorded in the inverter proves that the system efficiency is acceptable.
Thanks,
Geoff

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admin July 26, 2012 at 6:57 pm

Hi Geoff,

If the glass on a panel is cracked this could potentially pose a short or long-term issue, as moisture may leak in and affect the silicon cells themselves, although it seems that in your case this is not happening right now. Your panels and system should, however, most likely have a warranty that protects them against faults such as this. Contact your installer with regards to this, as they should be able to help you out–provided that a warranty does indeed exist. All quality products come with a warranty and it is a concern if they do not.

You might want to contact the Clean Energy Council about this issue. They are the independent body that regulates all things to do with solar power–including components and installers. They might be able to help you out.

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Carl July 21, 2012 at 5:33 pm

Great website with so much useful info. Thanks!
I have a new 4.6kW Motech PVMate 4600MS system with 2 strings of 10 panels. The uptime is 397 hours with only 496.4 kWh production in sunny Cairns over 37 days.
Should I be concerned? By my rough calculations, i am averaging 2.8kWh/kW per day which must be low for a sunny location.
What would you suggest?

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admin July 26, 2012 at 7:06 pm

Hi Carl,

Not sure what you mean by uptime, exactly, but an average of 2.8kWh (you do mean kWh, and not kW, right? the former measures total production, the latter refers to production at a given moment) is indeed quite low for a 4.5kW system. You should be getting about 18kWh a day in Cairns from a 4.5kW system in ideal conditions. What orientation is the solar array at? If the problem isn’t the orientation, then you might need to have your installer come back out and check that the components are all functioning properly.

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Brian July 22, 2012 at 8:46 pm

Hi

I live in the western suburbs of Adelaide in a single storey house. I have calculated that my daily average usage is approx 14.5Kwh. We have been advised that we need a 5Kw system comprising 19 – 21 panels depending on each quote and using different panels some panels are 190w and some are230 w.( is there any preference to the panel outputs.

The house has a north face aspect and due to asthetics we have decided that the panels would be installed on the western side of the roof and every company that has quoted agrees, this is due in part to a double storey home on the esaster side of our house that has potential shading impacts on my roof.

Can you please give me some advice as to
1 Is this sound advice
2 Can you direct me to a table for comparing solar panels (best vs worse) the reason for this is due to the sales pith that we get from the companies saying that other products specified by competitors are “cheap and/or not very good

Kind regards BJ

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admin July 26, 2012 at 7:14 pm

Hi Brian,

1. That is indeed sound advice if the house next door is going to be casting a shadow on your north-facing roof. However, you can expect about a 20% loss in output with a west-facing array. This isn’t a problem as long as you know what you’re getting into, which I expect you do.

About the 190W vs 230W panels, there is no substantial difference. The figure to watch out for in the end is the cost per watt of the system, not the size of the individual panels, provided they all fit on your roof. 190W panels are becoming less common and tend to be older stock, which is not necessarily a bad thing.

2. I can’t point you to that sort of chart, as which panel is the ‘best’ is a subjective issue, and will depend on your own needs and budget. Solar Choice does give free advice regarding solar panel installations. Start a dialogue with us by requesting a free, instant Solar Quote Comparison that will give you a broad look at the market in Adelaide.

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Mel July 27, 2012 at 5:06 pm

Hi,

Looking for advice on what system is best for us…. We live in Perth & We tend to use an avg if 15 units per day in winter costing $231, & an avg of 26 units per day in Summer costing $371. I am home in the day which I was told is great as this is the best time cram our electricity usage into. We had a quote the other day & it was suggested that we get a 9 panels x 240(w)= 2.16 Kw, with an inverter type -delta, size- 2.5 & apparently we can upgrade to 3Kw in the future… We feel this may not be big enough to suit what we use? I know it will reduce our bills but will this be enough to see a difference?? Understanding all of this seems very confusing… please help us to understand this a bit better.. ;-/

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admin July 30, 2012 at 12:36 pm

Hi Melissa,

Thanks for the comment. Just a few of points:

1) We do not recommend installing a system with a significantly oversized inverter unless you plan on adding the additional panels to ‘fill out’ its capacity within about 6 months from installation–which most people don’t end up doing. So generally we advise people not to go this route, as having an oversized inverter can compromise overall system yields.

2) You’re right that your system will only provide you financial benefit if you’re using power as the system produces power, so it’s good that you’ll be home. Getting the most out of the system really means, therefor, that you need to really pay attention to how and when you’re using electricity at home. Run things while the sun is shining as much as possible! Solar Choice has a Perth Solar System return-on-investment calculator that will give you some idea how you might benefit from a system, but please keep in mind that the figures are purely indicative, and real returns will depend on a number of factors, such as weather, your electricity consumption patterns, and the price of electricity.

3) Since there is no Solar Feed-in Tariff for WA residents who install a system now, there is no point in getting a system whose output will be more than your daytime electricity consumption. I see that you’ve requested a Solar Quote Comparison from our website; one of our brokers should be in touch with you soon to discuss your options, or you can give us a ring on 1300 78 72 73 to expedite the process. They’ll ask you to look at your power bills, so try to find a recent one.

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Benny August 1, 2012 at 8:34 pm

Qld has just reduced its FIT from 44 cents to 8 cents. I am building a new house but missed out on the cutoff to retain the 44 cents FIT. I live in Brisbane. At present I have a 2.5KW system in my present house and my avg. daily usage of my last bill for 92 days was 555kWh @ $0.027 and my solar bonus was 680kWh @ $0.52; giving me a Credit of about $208 per Qtr.
I was intending to install a 5KW solar system and with my supplier topping my FIT with another 8 cents (16 cents) total, I have been told that it will not be worth my spending $8,000 on the new system. Should I invest the $8,000 and what will be my ROI?

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admin September 6, 2012 at 3:53 pm

Hi Benny,

First of all, be careful, as installing a 2nd system may result in you losing eligibility for the 44c/kWh rate. The Queensland Government stipulates that there can be only ‘one application per premises‘ for the Feed-in Tariff.

If the 2nd system is for a different location, there are still strong arguments for going solar in Queensland under the 8c/kWh rate. The article linked there also has an (indicative) return on investment calculator, so you can get an idea of what payback periods are like for solar systems in Queensland now.

If you are interested in getting a 2nd system, don’t forget to come to us for a free and impartial comparison of solar quotes from installers in your area of Australia.

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Peter O August 3, 2012 at 12:07 pm

Excellent site with sound opinions & advice.
Just what the Solar Doctor ordered!
Thanks

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Ashley Sauer August 18, 2012 at 9:46 am

Hi

I am in Mackay Qld, and have a 4KW system comprising of 2 x 2KW Growatt Inverters each being fed by a 11 x 185w panels, which face west. The system basically work extremely well, and I am on 44c/kwh rebate scheme. I still havent reduced my electricity bill to zero yet.

I am wondering if it is possible to utilise the 2nd set of unused DC input jacks to connect extra solar panels on either the northern (or even eastern ) side of the roof, to increase the KW produced early in the day and therefore the kwh per day?
Currently in cloudless conditions, in the morinings each inverter is producing about 400-500 watts. At around 11am they produce 1500-1600w, then at midday till about 2.30pm, they run close to max power output. When summer is upon us these times will obviously increase.
Are there limitations on the system, or could I damage the system?
The inverter specs are as follows
Max DC power 2300W
Max DC Voltage 500V
PV Voltage range 120V-450V
Max No Parallel strings 2
Number of MPP Trackers 1
MPPT Inut current 0-12A
Max DC Input Isc Current 15A

The installed PV panels specs are as follows
Max Power 185w
Open Circuit Voltage 44.8V
Max Power (Vpm) 36.2
Max Power (Imp) 5.11

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admin September 6, 2012 at 2:33 pm

Hi Ashley,

It’s great that solar is working out for you.

Unfortunately, your inverters are already at capacity and it wouldn’t really benefit you to add any panels as the inverters can’t handle any more power coming into them–they only really operate up to their rated capacity.

You can read more about inverter efficiency in this article: Types of Inverter Efficiency.

Best of luck with your system!

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Julie August 20, 2012 at 3:18 pm

Hi, I’ve found this site very interesting and would luv someone to help us in making a decision. We are looking at a 5kw Fronius IG60HV inverter & 20 renesola JC250S -24Bb solar panels. We live in Lancefield, Victoria, our roofline faces north & our last bill said that we use 33kw daily consumption. We have 4 children under 12 and 2 adults. With all this info could you tell me what the daily output would be in kw from this solar system, the solar hours in our area,will the system bring our bills down( last bill was $733), is it worth getting a couple more panels added to make up for the tolerance in each panel to make the whole system run at full capacity! I’m sorry for all the questions just want to make right decision as it’s such a large outlay of money.$9330!

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admin August 20, 2012 at 5:41 pm

Hi Julie,

Lots of questions! One of our brokers would be happy to assist you and introduce you to some other options available to you in Lancefield. We are a 100% free service to our customers. Give us a call on 1300 78 72 73 or fill out the form to the right to receive a free and instant comparison of solar quotes from installers in your area.

To answer your questions quickly, $9330 is not a bad price for a 5kW system with those components. A perfectly designed and properly designed 5kW system in your part of Vic would produce just under 20kW/day on average throughout the year–more in the summer, less in the winter, of course. I imagine that with the size of the family you’ve got, you’re probably using a lot of electricity during the day, which is perfect, even if you don’t make the deadline for the Vic Feed-in Tariff. Hope this is helpful.

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Phil Shea August 22, 2012 at 2:13 pm

Mate,I,m led to believe that people around the place who have installed lots of panels are cleaning up on the Govervment feed in tariff. And as a consequence the Government have decreed that in such cases they,re feed in tarrif will be reduced. My panels get me to pretty much a break even point. An annual electricity bill of say $60-$80.If I go over the top and say,cover myself in blankets rather than use the air con while watching T,V. And actually come out in front financially, { lets say, the electricity provider pays me $50 or$60] does this mean that my feed in tariff reduce???? Cheers Phil

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admin September 6, 2012 at 12:48 pm

Hi Phil,

Thanks for your comment. Which Feed-in Tariff are you referring to? If it’s NSW, it’s certainly true that those who made it in on the 60c/kWh gross Feed-in Tariff are doing very well, as it was an extremely generous scheme (somewhat to the embarrassment of the Greens who helped get the program through state parliament and later saw the backlash that occurred in its wake).

Which feed in tariff are you receiving, if any? And which state are you in?

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Robyn October 4, 2012 at 11:28 pm

We live in Adelaide and have had a 3.2 KW system installed. We are not seeing the cost saving results that we expected.
Is there anything that we are doing wrong? The last billing period of 3 months we have only been producing 3 KWH per day according to our bill – but our solar is reading an average of 9kwh per day.

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Solar Choice October 10, 2012 at 11:50 am

Hi Robyn,

The difference in your meter reading and energy bill is because residents of South Australia are on a net metering set up. The 3kWh you see on your bill is what you export to the grid the ‘missing’ 6kWh is what you are using during the day.

There is not way to increase the energy you export unless you become more energy efficient e.g. hanging clothes out to dry instead of using a dryer or turning the air conditioning down or off. There are lots of energy saving website out there that will give you great advice.

We hope that answers your question.

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Thomas November 11, 2012 at 11:29 am

I have a 3.5 KW Growatt inverter with one string of 8 x 190 watt panels and one string of 7 x 195 watt panels. The watts they are producing are 1440 watts for the first and 840 watts for the second string. At any time of the day the wattage difference is aprox 60% but it should be ony 10%. Please help! Thanks Thomas

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Solar Choice November 12, 2012 at 10:41 am

Hi Thomas,

There few things you can check for. Is there shading on any part of the second string or at they on a different facing roof space than the first string (e.g. west instead of north)? Either of these will dramatically reduce the production of your panels. Is there any damage to any of the panels on the second string? Do they need cleaned? Do any of the panels look like they’re a different make or model? Were the two different strings installed at different times, performance will degrade over time so if you installed the 195 watt panels a few years ago they will be performing lower than newer panels.

With solar panels, they system only works as well as the worst panel. If there is an issue with one of the panels on the second string this could be bringing the whole performance down. If you contact your installer they should be able to come out and service your system (which is recommended every few years) and identify any possible issues.

We hope this helps!

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teddy December 15, 2012 at 7:13 am

I have 2kw system with 10 – 190w facing north and want to upgrade to extra 3kw with 12 – 250w facing west will SMA 5kw will work or I need another inverter.I have approved to put extra 3kw.

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Solar Choice December 17, 2012 at 11:38 am

Hi Teddy,

From what you’re saying you currently have a 5kW inverter with 1.9kW of panels attached and want add another 3kW to this. Technically this is feasible and I know some installers, who are not on our network, actively sell larger inverters with the promise you can ‘add on’ later. The problem you do have is that ‘adding on’ is not straight forward.

Hopefully your inverter will be a dual input inverter meaning that to can set up the 250 watt panels and plug them into this second input socket. You may need have have your cables upgraded but the installer should be able to advise you of this.

The worst case scenario is that you have a single input inverter. This causes a problem as solar PV systems only work as well as the worst panel, so your new 250 watt panels will only function at 190 watts at best and possibly a lot lower than this depending on the age of your panels. If this is the case you have a few options: find some 190 watt panels that are as close a match as possible to your existing system; replace all the panels with 250 watt panels, or stick with your current set up. Although the second suggestion sounds a bit extreme if it dramatically reduces your consumption from the grid thew ROI may be worth it.

Lastly please bear in mind any changes to your solar PV system may result in you loosing your current feed-in tariff, your energy provider and installer should be able to help you with this.

We hope this helps

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Hany Azzam January 5, 2013 at 8:52 pm

Hi, I live in Punchbowl in NSW. Recently I got a 2kw Trina Solar installed along with a Delta inverter. Today the 4th of Sydney the inverter showed that it produced 13,340wh which 13kwh. Is this correct?

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Solar Choice January 7, 2013 at 3:40 pm

Hi Hany,

When we talk to customers about how much energy their solar system will produce we normally advise an average of 4kWh per kW installed. As we’re in the middle of summer with longer day light hours and the beautiful sunshine your panels will be generating for longer and at a higher intensity.

We hope this helps

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Tanya Alonso January 7, 2013 at 10:09 pm

I got a 3 Kw solar system installed last month – 12 X 250W Polycrystalline LDK panels with Omniksol 3.0k TL Inverter. The inverter allows for remote monitoring via wi-fi and I’ve been watching the performance of the system for its 20 days of operation so far. All panels face West (even slightly NW) and there is no any shadow cast at any time on any of the 12 panels. The tilt is approx. 22-25 degrees. What I would like ask is whether it’s normal that the highest peak power generated so far on a really nice clear sunny day is between 1650-1700W with only 1 exception of 1980W after a period of cloud. Now I understand that I can’t expect to get 3.0Kw (as peak) since my system is facing West and I believe I automatically loose around 10-20% efficiency but what I get is actually bordering 50%. Am I right to think that there maybe something wrong (with the installation?) and what do you think the possible reason for that low peak power might be? Do you think I should contact the company which I purchased the solar system from or the subcontractor who installed it.
Thank you very much for your support!

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Solar Choice January 9, 2013 at 11:51 am

Hi Tanya,

I’ve just spoken with one of our team who is a qualified electrician and used to install system before moving to Solar Choice. Given the details you’ve passed on he suspects it’s an electrical issue and advises that you contact the installers to arrange for them to come and check the system. Check your warranty as you may have a clause which would cover this call out.

If the electronics are wire correctly the other option is the inverter, Omnik Inverters are not used by any of the installers on our network and I’m not familiar with their products. I’m slightly concerned with the poor English on their website, the better quality manufacturers tend to spend the time getting the small things right. If it turns out that this is the problem I would try switching to a different manufacturer, you can research the different options online. Whirlpool forums are great for getting feedback from people who have dealt with both installers and manufacturers.

Generally we advise that people spend some time doing their own research before signing any contracts. We do the due diligence on behalf of our customers but it’s always great for customers to go that extra mile to ensure they’re really comfortable with what they’re signing up for. Look for companies that have been around for a while are generally a good choice, a companies website is a good indication of whether they’re investing in the long haul and reviews from other customers (try getting ones in the last few months) are a good indication of performance.

Hope this helps.

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ray January 12, 2013 at 1:54 pm

I have a 16 panels/3kw JSI 3000TL grid connected inverter (CHINESE MAKES ) and I have noticed that my panels are now a mixture of blue and black . This was not the case when they were installed 10-2-12. I have been experiencing larger than normal power bills of this period .My panels are on a tilt system and I live in Hallett Cove south of Adelaide and have full sun for 100% of the day What I have stated Re: the colour of the panels ,IS THIS NORMAL APPRECIATE any comments you have Regards Ray

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Solar Choice January 14, 2013 at 11:12 am

Hi Ray,

Although you’re panels can change after they are exposed to the elements it’s not normally a huge change. Mono panels should all be uniformly dark, while poly panel will have a range in colour.

If you’re panels started dark and have discoloured to a light blue colour this suggests that something could be very wrong. We had a visit from a premium panel manufacturer and he showed how their panels perform over time compared some of the less reputable manufacturers, the panels who’s performance decreased significantly over time had turned light blue.

The other thing you might want to check is the inverter, generally speaking we encourage customers to go with European manufacturers because the Chinese products just aren’t up to scratch, although we’d be happy to be proved wrong.

I would contact your installer and get them to come and check your system, if it turns out it’s an inverter issue and they offer to replace I’d recommend investigating the possibility of upgrading to a European model. SMA, Fronius and Aurora are reputable brands but you can research anything else you’re offered on the internet before going ahead.

We hope this helps and it’s only faulty wiring not the components that are the problem!

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kurt February 8, 2013 at 11:24 pm

Hi,I have had a 3kw system on a north facing roof for just a year. The panels are 12x LDK 250 D and the inverter is an Aurora 3kw. I have noticed that the peak output of the system has not exceeded 2140 w since the start of this year and was only 2150 last year. The reading on a sunny day is around the 14.5kwh mark. This would seem to indicate the system is producing approx 2/3 of its rated power. Is this reasonable or is there a possible problem I should follow up? Thanks Kurt

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Solar Choice February 19, 2013 at 3:02 pm

Hi Kurt,

With all the variables optimised, your solar PV system should operate at about 90% efficiency. A one year old system operating at 60-70% does sound like there is a problem. In an ideal word your panels will face due north and be tilted to a degree that is a little lower than the line of latitude your house lies on. You might want to check that there is nothing shading your panels (including themselves – unfortunately we have come across this from installers not on our network), if one panel is even partially shaded it will effect the output from those on the rest of the string.

As the problem has been ongoing for a year, it might also be worthwhile getting the installer out to service the system. Issues with the wiring or the inverter would dramatically effect the reading on your meter.

Hope you get this issue sorted soon.

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Frank February 18, 2013 at 3:37 am

Calculating the energy output of a solar system can be rather complex. The formulas to use are difficult for a person that has no or little knowledge of elementary physics.

There are several sites that provide an easy way to calculate the energy output of a solar system. For example on http://www.sustainableenergyworld.eu/solar-panel-energy-output-calculator/.

The calculator on that page first determines the maximum capacity in Watt of your solar system by asking you the number of panels and the maximum capacity of each panel. Then the revenues of the system are calculated depending on where you live. The revenue is given in kWh/year. Finally a correction is made for the actual placement of the panels depending on the irradiation factor. The irradiation is a function of both the orientation and the inclination of your solar panels. You only have to supply the orientation and inclination in degrees to finish your calculation. The calculator gives you the result in kWh/year. Furthermore the calculation method used is explained in a clear way. Worth a visit!

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Solar Choice February 20, 2013 at 10:13 am

Thanks Frank!

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Patricia Mitchell February 27, 2013 at 5:26 pm

Unfortunately this calculator only covers Europe. So, no good to us.

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Solar Choice February 28, 2013 at 9:23 am

Hi Patricia,

We’ve found one that works globally at EcoWho.com, visit http://www.ecowho.com/tools/solar_power_calculator.php. There is no perfect answer but this should give you a good idea.

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Deepak March 20, 2013 at 3:09 am

Sir. How much area is required to make around 100kwh(4*24) per day? I my area we receive sunlight for 5-6 a day.

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Solar Choice March 20, 2013 at 4:59 am

Hi Deepak. You’d need approximately 20kW of solar panels to produce 100kWh of power per day. The area will depend on the exact panels used, but assuming an average-sized 290W panel (1.954m x 0.982m) is used and the panels are laid flat, approximately 6,620 square meters of are would be required.

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Tony Van Der Ark May 5, 2013 at 2:37 pm

Hi, I have 3kW of panels and a 5kW growatt invertor. North facing at 30 degrees tilt and zero shade. I have 2 questions…. what instantaneous wattage should I get at Noon? and secondly, what total gereration on a cloud free May Autumn day? Have had issues with the unit and can’t seem to get reliable advice on what I should be getting. Thanks !!

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David May 9, 2013 at 6:45 pm

Hi I am answering a question for my uni assignment and its on “Is the efficiency of Solar Panels improving”?

I need some statistical data preferably graphs that show a trend of solar panel conversion efficiencies improving over the years and predicted efficiency conversions well into the future but i’m not sure where to start with my research, any suggestion guys?

Kind Regards

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Solar Choice May 14, 2013 at 7:41 am

Hi David,

There have been lots of developments that promise to improve solar panel efficiency have been taking place, but it’s hard to predict which ones will be adopted first. A big factor is commercialisation–whether these technologies can be implemented economically. Conventional silicon–currently the most popular technology–might even be usurped by other materials like graphene.

I’d recommending looking towards Bloomberg New Energy Finance (BNEF) and McKinsey for some actual past and predicted future figures.

Good luck with your project!

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Harsh August 20, 2014 at 4:51 am

Hi,

Nice summary. I am a novice and would like to setup a mini solar electricity generation system in my roof. But I have no idea what all things will I be needing to do it (Exhaustive I mean). Assuming I have a 500W 24V solar panel, what else should I need to make it usable for household use – 220V AC.

As far as I browsed, I would be needing a charge controller, battery and an inverter. So, what would be the config of these devices which would be required in my case and also are there any other things I would be needing?

Thanks a lot for someone who takes time to reply to this.

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Solar Choice Staff August 21, 2014 at 3:44 am

Hi Harsh,

We’re not in the position to tell you what you’ll need if you’re planning on installing the system yourself, although it is certainly possible (especially if you happen to be an electrician). Getting a solar installation kit (with all parts included and designed for a 220V AC home) might turn out to be an easier choice than piecing a system together from individual parts.

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Harsh August 25, 2014 at 1:30 am

Thanks for the reply.
I am just wondering how hard could it to be to assemble such a setup. Should just be connecting few ready-made devices properly, noe..!
Anyways, thanks again.

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D hayes August 8, 2012 at 4:18 pm

I have been told that the 2 strings are very close in voltage. I donot know if each panel has been tested, but wouldnt this show up on one of the strings if a panel is faulty? I have been in contact with a number of people (including the installer and gren energy council) and have been told my system appears to be poviding reasonable daily kwh. No one can tell me why my brothers system is repeatedly providing him with at least 100% more kWh than mine per day. I would appreciate any further advice.

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admin August 22, 2012 at 5:51 pm

Hi D,

This one has proven to be a tricky issue. I’ve spoken to a independent consultant with a longer history in the solar industry than myself and he suggested the difference in outputs between the two systems could be due to differences in the panels’ power tolerance. An XH solar panel datasheet that I found here says (rather confusingly) “High reliability with guaranteed + 3% power output tolerance”. Usually power tolerance figures are listed in the form “-3%/+3%” or “-0%/+3%”, for example. I presume the latter is what they mean.

Power tolerance figures indicate how much actual power output could potentially vary relative to the nominal capacity of the panel. A 250W panel with a -0%/+3% power tolerance would therefore produce anywhere from 250W to 257.5W at standard operating temperature. If all of the panels in your brother’s array just happen to be on the higher end of the power tolerance, this could explain why your brother’s system is producing significantly more power than yours, especially if there is some other as of yet unidentified issue pulling down the output of your panels.

Apologies if this doesn’t answer all of your questions. Hoping that you get it figured out.

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D hayes August 27, 2012 at 9:07 am

Thanks for your assistance. I have increased my system to 4.5 kw. I guess the system is what it is and the reason for my brothers system producing a lot more kwh will remain a mystery. Just one last thing, do you know of any company or person in melbourne that could do a complete test of my system?

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admin September 4, 2012 at 6:35 pm

Hi D,

You may have to pay an installer to do the test. I don’t know of any offhand who offer such a service (it’s not ordinarily advertised) but I would recommend simply Googling ‘solar power melbourne’ and finding an installer that has an office in the area. Check with a few before you reach a final decision, though.

Good luck with your system!

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D hayes September 26, 2012 at 9:33 am

Thanks again for your comments. I just have one final question (i think). I have noticed that on cloudy days my inverter is producing lets say 1.5kW. When the sun comes out, this will increase rapidly to approx 3.5kW. If the sun stays out, the production will slowly reduce and settle around 3.1kW. can you tell me why this happens?

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Solar Choice September 27, 2012 at 10:24 am

Hi D,

It might sounds strange but solar panels prefer cold but sunny conditions. When the sun first comes out after a period of cloud the panels are cool and can function at their optimum capacity, as the panels heat up in the sun they loose some of their conversion efficiency and this is why you see a slight reduction in the energy produce even though it’s still sunny.

Hope this helps!

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