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,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.

Whether or not you have access to a solar feed-in tariff (keeping in mind that all of the feed-in tariffs in Australia have been closed to new applicants), you should know how many (kilowatt-hours or kWh) your solar system can be expected to produce. Knowing this number will help you calculate the revenues and savings you can expect to receive from your solar panels.

What factors influence solar system energy yields?

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. The USA’s National Renewable Energy Laboratory’s (NREL) PVWatts tool also works for Australia (using Aussie meteorological data) and is a great resource for plugging in numbers and estimating a solar system’s output. We encourage you to check it out.

Some exploration will reveal 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

{ 79 comments… read them below or add one }

Mark December 10, 2011 at 8:07 pm

Hi i was wondering if anyone could tell me the best tilt angle for burpengary which is about 30ks north of brisbane kind regards mark.

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admin December 19, 2011 at 11:50 am

Hi Mark,

The rule of thumb for systems outside the tropics is to tilt the panels at the same degree as the latitude. Solar panels in the Brisbane area should be fine at about 30 degrees.

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Ralph Lowe December 10, 2011 at 1:54 pm

I have a 3kw system on flat roof (10deg) facing north with no shading in Melbourne.
The system produces peak outputs of around 2.4 – 2.6kw with very occasional spike of 2.8 on an overcast day when there is a break in the cloud so presumably panels are a bit cooler and more efficient. Given we are now into summer with sun angles almost straight overhead at mid day I would have thought the system would be hitting closer to 3kw peak rating. Is it likely I have a panel not working or is this just typical heat derating? Appreciate your comment.
Thanks

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admin March 19, 2012 at 11:03 am

Hi Ralph,

Thanks for the comment.

The figures you’re quoting don’t sound unrealistic when heat derating is taken into account. Since all systems have inefficiencies, it is usually more useful to look at the overall daily output of your system than the instantaneous output. Taking inefficiencies (heat derating, inverter efficiency, dirt on panels, wiring, etc) 3kW system in Melbourne can be expected to produce about 11.5kWh of power per day. Broken down, this is 3kW * 3.8 sun hours. Some people do solar system output calculations without taking into account inefficiencies–e.g. 4.6 sun hours * 3kW = 13.8kWh, which is higher than what should reasonably be expected. So for the most part, it sounds like your system is doing what it should do.

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chris November 29, 2011 at 12:34 pm

I have a 1.5kw klein inverter with 9 x 180 w panels on a 45 degree tilt roof facing north with no shade. I get around 5.2 to 5.5kwh at this time of the year November. I think this is quite effecient? Appreciate your comment? I am located in melbourne.

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admin November 29, 2011 at 5:15 pm

Hi Chris,

Thank you for commenting. In November in Melbourne you should be able to expect about 6.1 sun hours per day, so (1.5kW * 6.1=) 9.15kWh. Even if it is perfectly sunny and you have no shading issues, there are other factors that might be affecting your system’s performance–including heat. What brand of panels have you got installed, and what is the heat derating coefficient?

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Karen November 15, 2011 at 10:49 am

We live on the Gold coast and had our system sine ce Apr, we have 10kW of solar panels and a 10kw inverter, on a an overcast day we will make 8-16kW, our best day to date is 62kwW. How do out figures compare, we have mostly north facing panels, some on the southern roof ( we are considering tilting these up? not sure if it is worth the money to do it) Also we have a few panels on the western roof as well. I would be interested to hear your thoughts. Why is it that some 10kW systems are ~ $28K and others up to $48K ( is there really that much difference in the quality of panels and inverters?

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admin November 28, 2011 at 11:33 am

Hi Karen,

Thanks for the comment.

First off, it’s important to note the difference between ‘kW’ and ‘kWh’–kW is the capacity measure of a system, or the instantaneous power output at a given point in time, whereas kWh are the measure of the energy produced. Perhaps you just forgot to put the ‘h’ at the end, but I wanted to clarify anyhow!

In any case, it sounds like your system is performing pretty well. The annual average for sun hours around the Gold Coast is 5.4. Multiply this by 10 and you have 54kWh per day on average across the year with a 10kW system. Since we’re almost in December now, you can be expecting a bit more sunshine than the yearly average–about 6.3. Multiply this by 10kW, and you’d be able to expect about 63kWh per day. This is almost exactly what you say your system is producing, so I think it’s safe to say that your system is a textbook example of how the calculations should work! I hope you’re happy to hear this. Of course, on the cloudy days you can’t expect nearly as much power out of your panels, but there’s nothing anyone can really do about that, is there?

In relation to your question about system prices: The variation in the market is due to a number of factors–quality of components, installer overhead, remoteness of the location of the system to be installed (travel costs may be incurred), whether the system is a ground-mounted solar array or roof-mounted, etc.

Solar Choice’s role is to impartially asses the systems and prices on offer from our network of installers from region to region across Australia and assist our customers in deciding which systems that best suit their budgets and needs. This gives us a bird’s eye view of the solar power market. Several years ago $40,000 for a 10kW system might have been acceptable, but nowadays $30,000 is a bit more in the ballpark. Through research and market analysis, our Solar Energy Brokers have even come across systems as low as $20,000 for a 10kW solar power system with decent quality components! This is admittedly a rare case (possibly unique in Australia), but we have witnessed the price of solar power come down dramatically in the past few years, so it does not come as a total surprise.

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Raymond Lobo November 10, 2011 at 1:02 pm

In relation to question 1, I have found out that the ETSA smart meter is an import/export meter; so one reading is what has been put back into the grid. Yesterday my system generated 17kwh; 13.1 kwh was put back into the grid. So I assume, the solar also contributed approx 3.9 kwh towards the consumption which would normally have been an import. Does this make sense?
Thx
Raymond

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admin November 25, 2011 at 12:13 pm

Hi Raymond.

Yes, that’s correct. You used the 3.9kWh in your home, so it was not exported to the grid. Only excess electricity produced by your panels when you are not using it is exported.

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Raymond Lobo November 9, 2011 at 9:23 am

Hi – find this a fantastic webiste. Am keen to get some feedback and provide some information for your stats as well.

My 3KW system was installed yesterday in Adelaide. It has 14 panels (Suntech STP 220 – 20 Wd, Clenergy Inverter). Also have the smart meter installed by ETSA. (North East facing – 30 Deg)

1) Yesterday, at the end of the day (was only put into operation at 2:30 pm), noticed a difference between the ETSA smart meter and the Inverter panel (the invertor showed it had generated 2KWh for the day, the ETSA meter 1.3 kwh for the day) – wondering if this is because the ETSA METER gives a reading which is what is being used in the house minus what is being sent to the grid?) Any idea?
2) Also the clean energy council says a 3kw should generate on average12.6 kwh daily. Is this an average across the year? So in general should I be expecting in summer say 15 – 16 kwh per day and in the winter 8 – 10 kwh per day; such that the average across the year is 12.5 kwh per day. General question – understand that there could be a lot of variations etc, however there is no shading etc on the panels
3) Probably a question I am going to regret since already installed – but are the panels and inverter in general – on average, above average or below average
Regards
Raymond

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admin November 25, 2011 at 12:20 pm

Hi Raymond,

Thanks for the comment. The responses to your questions are below.

1. You’re right that the meter will show what is exported to the grid. What is exported to the grid (and what you get paid for) is the electricity your solar panels produce minus what you use domestically (and therefore don’t get charged for.)

2. the 12.6kWh is an annual average–you will see variation throughout the year.

3. Since your system was only put in at 2:30, you wouldn’t expect a full day’s worth of electricity to have come from it, so it’s hard to judge. Have you got any more recent figures?

Hope this was helpful.

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Brian E November 8, 2011 at 2:14 am

There is a special on at the moment here in Perth which has a 4.2kw Growatt inverter with 8 190W ceeg panels for $2299. I don’t know much about this technology but wouldn’t you need a load more panels before you could make maximum use of the inverter? I have already got a 1.5 system on the roof but putting up another would mean me losing the 40c rebate, so i’m not sure whether I’ll be ahead, especially as it would cost me closer to 5K to install, because you only get one govt refund. I don’t know whether this piecemeal approach would be beneficial. Any thoughts?

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admin November 9, 2011 at 5:32 pm

Hi Brian,

Thanks for the comment. The combination of a 4.2kW inverter with 1.5kW of panels is an interesting one to say the least. You’d want to check the production curve of the inverter to see if such a system would even be worth considering in the first place–inverters need a minimum voltage to switch on, so if your panels don’t meet that, you’re not going to be getting much juice out of your system.

The second thing is that the price of the system as advertised almost certainly includes the REC price–the up-front ‘subsidy’ given by the federal government for renewable energy generation systems. Individuals are only eligible for one Solar Credit rebate per premises, so this will not be applicable to you. As you pointed out, the actual cost of the system may end up being much higher if it is the case that the RECs have been included in the advertised price.

Finally, it is not possible to increase the size of your current system and still be eligible for the 40c/kWh WA Feed-in Tariff that you are currently receiving, so even using the parts from the new, cheap system would still mean significantly longer payback periods. Unless you use lots of electricity during the day and your electricity bills are quite high, it doesn’t seem like it would be advisable to purchase the system you’re talking about.

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Sean B November 6, 2011 at 6:27 pm

I must be drunk, I meant to say that there has been no shade whatsoever, NOT no sun. It has been cloudless days.

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Sean B November 6, 2011 at 6:25 pm

Hello,

I believe I have a problem with my system but just want to check before contacting the company that installed them. They were installed last Wednesday and the inverter that came with the system tells me that the panels are only working at 60% effeciency. This shouldn’t be the case, as I have pretty good conditions for the panels.

It is a 2kw system, the roof has a pitch of 16 degrees, the roof faces 10 degrees off true north at 350 degrees, there is no sun whatsoever at any time of the day, the roof is colourbond sand colour, and there is no shade from any other sources. Yet at numerous times between 12noon and 2pm in the prime of the day, with no clouds, full sun, and a cool breeze at times (hence eliminating a heat issue) the system is only producing between 1.4 and 1.5 kws, from the 2kw system. Shouldn’t I be expecting a better result?

The only thing that may impact on the result is that it is a 3kw inverter, but that shouldn’t make too much difference should it?

Any help would be very much appreciated!

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admin November 25, 2011 at 12:09 pm

Hi Sean,

It’s hard to say exactly what the problem might be without seeing the system, but it could very well be an issue with the inverter being undersized. What brand of inverter do you have?

You can read more about inverter efficiency curves and types of inverter efficiency in these articles.

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Lesley November 3, 2011 at 4:05 pm

Hi,
We’ve had a 2.0 kw system installed in Dubbo & our system is generating about 13.12kw per day, so we’re pretty pleased with that.

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Tania November 1, 2011 at 7:50 pm

Thanks for the fast reply with the info. Yes we thought we’d be better off installing a bigger inverter with the aim of adding another 4 – 6 panels in 6 – 12 months. Difference in cost was approx $1000. We couldn’t fit all the panels on the roof facing north thus we had to split them up, though the sales man said this would only have a small effect on efficiency.
Yesterday the weather was sunny, clear & 29*c & we totalled 21.5 units for the day……i think we’re happy with that???

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admin November 2, 2011 at 9:59 am

Sounds like, fortunately for you, my estimates were a bit low! Your system is performing phenomenally well. It may have something to do with your roof angles–is your west-facing roof at a low angle?. It may also be due to the fact that I was using the yearly average as opposed to a season-specific number of Peak Sun Hours–5 as opposed to, say 7. Enjoy your system and your savings!

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Tania October 31, 2011 at 8:26 pm

Hi there,

We have a Sunny Boy 5000TL inverter with 18 x SF 190 panels. 10 panels facing 0* N, 8 facing 270* W on dark colourbond roof. No shade at all from buildings or trees etc. We are situated approx 20km north of Perth CBD. We have only just had the system installed & were wanting to know what the highest possible reading we can expect from our system on an ideal day. Going from our previous electricity bills on average we are using 15units per day. I am hoping to cover the bill entirely in the future :)

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admin November 1, 2011 at 11:20 am

Hi Tania,

Doing some quick back-of-envelope calculations, you could expect up to 11.8kWh on a good day, but this number may well be lower depending on how your inverter handles the two strings of panels, with are of disparate capacity. If all the panels in your system were facing due North and both of your strings were the same size, you could expect to just about be able to cover the 15kWh/day that you’re currently using.

I notice that your inverter (nominally 5.0kW) is oversized for your solar panel array (currently about 3.42kW–although this isn’t really an accurate description of capacity because of the different orientations and voltage levels of each string). Fortunately, with the particular make and model of inverter that you have this is not a huge issue, but you are losing a bit of efficiency. Did you install the 5000TL inverter with future expansion of your solar panel array in mind? That’s why people usually install an oversized inverter.

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Toni October 18, 2011 at 9:04 pm

Hi there, I am just wondering what my 5 kw system which included 21 panels should produce. On average 28 degrees temp with panels facing north with full sun for at least 9 hours. We have only been averaging between 20 and 25kw per day but we were Expecting a lot more and we were told by the sales man when we signed up that we should still produce 17kw on a cloudy day.
Our neighbor has a 3kw system with only 16 panels and he is producing almost the same as us and his system was $10,000 cheaper.
I hope you can help..

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admin October 20, 2011 at 10:59 am

Hi Toni,

Thanks for the comment. What type and brand of panels do you and your neighbour have? Some types of panels perform better than others in hot conditions, and this may be your problem. If that isn’t your problem, there may be other, balance-of-system issues that may need to be looked at.

If you get back to me with the panel information (try to get your neighbour’s as well), I can do some quick calculations to see if overheating might be the issue.

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Tim September 3, 2011 at 1:32 pm

If I have a 1.5kW solar system, does that mean it is producing 1.5kW power at any time given a fully sunny day?

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admin September 5, 2011 at 12:04 pm

Hi Tim,

Thanks for commenting on our article.

As the sun moves through the sky, it casts varying amounts of light on your solar panels. You will only get the full 1.5W of electricity produced when the sun is shining directly onto your panels. You can therefore expect less output from your solar system in the mornings and afternoon because the angle of the sun would be less than what is optimal.

So the short answer to your question is no, a 1.5kW system does not consistently produce 1.5kW of power throughout the day–it would only produce this amount when the angle of the sun is shining on it at the best angle angle and orientation for solar.

There is solar power jargon for the cumulative sunlight that shines during the course of a day–PSH or ‘peak sunhours’. This unit measurement of daily sunlight takes into account the differences in sun angle throughout the day, consolidating it into one easy-to-understand number. You can read about peak sunhours and average daily solar system production in this article.

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Ambika August 24, 2011 at 7:23 pm

While surfing i came across this excellent site.
Sir i have a doubt..
If i am using 1.5 KW Solar system what will be my monthly energy and how do i calculate that.. I am from india i am planing to install solar panel on my home. Give me a general idea on this.. i hope you reply me soon…

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admin August 25, 2011 at 9:21 am

Hi Ambika,

We usually only answer questions about Australia, but I’ll try to give you a basic answer to your question.

The answer to your question would really depend on how many peak sun hours you get in your area of India. You can see such a map here. (This is similar to the map in our article about RECs/STCs and the different solar insolation zones in Australia.)

If your system capacity is 1.5kW, on a clear, sunny, cool day, you should be able to determine how much electricity your system will produce simply by multiplying 1.5kW by the number of peak sun hours you get on average in your area.

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dianne rhodes August 24, 2011 at 11:07 am

hi there. just wondering if you can help me optimize my 1kw inverter and system. i currently have 6 x 170w panels. rated power output 1.02. i was getting a 2kw system but there was quite a delay, and wouldnt have been eligble for the full rebate, so settled for the 1 kw instead. they have placed the panels northwest, as i have a double storey next door and assumed that would block some of the light.
it seems though that im producing next to nothing, which makes me wonder why i waited a year to get them!
according to your chart, i should be producing 3.6kwh per day based on a 1kw system? i would be lucky to get 1 kwh.
it doesnt help when the electricity company cant get the bills right either!
can you work out what i should realistically be expecting, and if moving the panels is an easy answer? can i add more panels to the current system?
hope you can help.
dianne

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admin August 25, 2011 at 9:42 am

Hi Dianne,

Sounds like a tough situation. I can’t answer your questions in detail without knowing the specifics of your situation. However, I can say that if you’re getting even partial shading on your array from the house next door, it is not impossible that your system would be producing the amount of energy you claim that it is currently producing–1kWh. You are right that this is significantly less than what you should expect per day from a 1kW system.

I don’t know where you’re located, but I presume (because you said you should be producing 3.6kWh/day) that you’re probably on the southern end of the Australian mainland–this may be the case in winter, but the angle of the sun may change in summer, and you might see an uptick in production. When did you have your system installed?

About adding extra panels–I would only suggest doing this if you are sure that the new panels will not be shaded! Other it will be all expense for little benefit. Moving the panels might be a slightly better option–if shading is indeed the cause of your problems.

Also check out our article about how to troubleshoot your solar power system.

I hope you find this helpful.

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Robin August 14, 2011 at 2:08 pm

Apart from area, is there any advantage/disadvantage in using say 12 x 250 watt panels as opposed to 16 x 190 panels? How do they compare in efficiency and cost?

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admin August 15, 2011 at 10:59 am

Hi Robin,

The efficiency and cost of any panels have more to do with the brand/manufacturer than the actual rated power of the panels. What brand are you looking at?

The only inherent advantages and limitations that would differ between the two combinations you mentioned is how the arrays can be configured. Depending on your system’s inverter, you may have to have a certain number of ‘strings’ of panels to achieve the correct voltage. Also, if you have any shading issues, you would want to configure your strings to minimise the impact of this–something you would have less flexibility with with a 12panel x 250W system.

I hope you found this helpful. Remember that we offer free solar installation quote comparisons nation-wide. You will have one broker to walk you through the process and help you to choose the installer and system that are right for you. You can also give us a call on 1300 78 72 73.

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bob August 8, 2011 at 11:46 am

hi, we have had 16 190kw panels and 3kw Aero-Sharp inverter installed we live in cairns the roof pitch is around17 degrees facing nw the best output we have had was 9.1 kwh our friends have 16 175kw panels and 4kw inverter. on the same day their output was 14.4kwh they live 2k from us and face nnw there was no cloud that day and they get some morning shade from neighbours trees seems to be a big output difference any ideas how to boost output?

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admin August 9, 2011 at 10:13 am

Hi Bob,

It sounds like your tilt angle is perfect for your location–latitude and tilt angle should be about the same or +5 degrees. Your latitude is 16 degrees, and your solar array tilt angle is 17. And NW is not a bad orientation.

That sounds a bit strange, for sure. We have an article about troubleshooting solar power systems for problems with output. This may help you a bit.

If you can’t find any answers there, I would recommend contacting your installer to have a look. You may be dealing with some kind of component problem. What components are used in your system?

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bob August 9, 2011 at 8:48 pm

hi thank you for reply have contacted installers they will send someone to have a look next week
not sure about components used will have to wait and see if they can find anything

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admin August 10, 2011 at 9:16 am

Thank you for coming to us with your question, Bob. Good luck with your system.

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Tommy August 7, 2011 at 10:39 pm

Hi I just want to ask you, I originaly paid for 7 solar panels at 1.5 kw thrue my electrical company , but after they istalled them, i noticed it was alot more than 7 panels. Its been bothering me, so on my enverters lcd screen today I checked it had (system 171w ) and below it (today 3.004wh) it was cloudy and lightly raining and around 18 to 20 degrees in aearly august in sydney . so what I wanted to know did they install to my benefit more panels than I asked by mistake? also on my first bill i had (solar Pv buyback 490kW for 78 days)
If you could reply i would greatly appreciate it. Thanks

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admin August 8, 2011 at 10:41 am

Hi Tommy,

Thanks for the comment. I think you can consider yourself lucky if they installed extra panels by mistake. How many are there? You might even want to call them up and ask if they did it by mistake–it’s unlikely that they’d actually charge you for them at this point. I can’t see any reason for them to install extra panels without telling you why they did so…

The numbers you mentioned don’t mean a lot without a bit more context. 171W was the system reading at the moment you looked at it, while 3.004Wh was the total amount of electricity produced during the day up until that point. The numbers are very low–not a surprise for a rainy, cloudy day! The important question to ask is how much your system produces on sunny days.

The important thing to remember is that W (watts) is the instantaneous measure of power (it will constantly fluctuate as the sun moves through the sky and passes behind clouds, etc), while Wh (watt-hours, or kilowatt-hours) is the measure of the total electrical energy produced across a period of time–for example, 1 day.

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George July 27, 2011 at 8:09 pm

Hi, I have a 3.8kw system (20x190w panels) with a Xantrex 5.0kw inverter.
Panels face around 10 deg.
I have a little morning and afternoon shade.
I have mono panels
The system created around 13.7kw for yesterday which I am happy with.
I live SW Brisbane.

A work mate has just had a 1.52Kw system (8 Panels) and a Xantrex 3.0Kw inverter.
Not sure on his panel direction.
He claims full sun all day.
He claims 12.7Kw for yesterday .
He lives east Brisbane closer to coastline.
From what I gather a 1.5kw system should only see 4 to 7 kw/day.
How is this possible ?
Perhaps he is reading the display wrong or could it be faulty ?
My sytsem cost $11,000 more than his.

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admin July 29, 2011 at 10:24 am

Hi George,

I’m not sure what to say! Your friend’s system shouldn’t be producing that much electricity in one day, especially in winter. On an average Brisbane July day, you should be looking at (4.2 peak sun hours X 1.52kW system =) 6.4kWh at most!

Yours, on the other hand, would be (4.2 peak sun hours X 3.8KW =) 15.9kWh, but as you said, you have some shading problems and a less than optimal tilt angle. So your system is performing quite well, I think.

You might want to have a look at your friend’s system and monitoring equipment. Or you might just need to question whether he’s telling you the truth, trying to one-up you with claims of superior system performance. Something doesn’t sound right with his figures…

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Brian August 2, 2011 at 11:06 am

Hi Admin, George,

I have a system that sounds identical to your friends (1.52Kw system (8 Panels) and a Xantrex 3.0Kw) and only managed to get it turned on over the weekend. Took Energex two months to upgrade my metering :-( . With an almost perfect roof (26 degree picth and only 4 degree of true north) I generated 8.203kWh yesterday. Sat and Sun I did approx 7kWh with some slight cloud during the day.
So 12.7kWh sounds very high but can quite comfortably achieve more than the 6.4kWh that has been mentioned as the “at most.”

What level of generation from the panels would the inverter normally cut out. I believe this can make a big difference as I have been advised that the cheaper inverters can cut out when generation starts to drop down to a couple of hundred watts. Is this true? as I have seen the reading on my inverter show 40W just after 5:15pm ( the sun was just about completely down) but it is still generating.

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admin August 2, 2011 at 12:18 pm

Hi Brian,

Thanks for the response. You are right about 6.4kWh being a bit low for ‘at most’–some panels actually produce more than their nominal capacity, so around 8kW is feasible, especially considering that my estimation was based on the minimum peak sunhour number of 4.2kW. Right now (in August), it’s actually a bit more than that.

13kWh, in any case, seems pretty incredible for the current level of insolation for a 1.52kW system.

About the inverter cutting out: with the Xantrex 3kW, you would see the efficiency begin to drop significantly when your array output drops to about 100W. You can see a chart of the efficiency curve at the bottom of this document.

Hope you found this helpful!

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doris July 3, 2011 at 5:36 pm

I have had installed 18 panel solar system facing west in melbourne what kws should this system produce per day

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admin July 4, 2011 at 11:47 am

Hi Doris,
That would depend, first of all, on your solar panels. What is the rated capacity of each of your solar panels?

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DAVE EADE July 2, 2011 at 9:24 pm

I Like to know how much 5x 4(kw) would cost solar panels

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admin July 4, 2011 at 10:19 am

Hi Dave,
The answer to your question depends on the solar installer, your location, and a few other factors.
Give us a call on 1300 78 72 73 if you would like to discuss your options. Solar choice offers free quote comparisons of different installers who operate in every region of Australia.

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kevin June 16, 2011 at 8:56 pm

I have had installed a 6.3kw inverter with 30 X 210 Watt Solar Panels Roof is facing North with a 22 deg pitch. Located on the Gold Coast in your opinion what sort of yield should I obtain in Winter?

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Rosemary Taffinder April 22, 2011 at 8:10 am

I have just purchased a 2kw solar sytem panels (11 panels) i have just recieved the first bill which was taken from January to April in Melbourne. We have had a very lot of sunny day. On my solar panels i recieved a solar buy back of 126 kw. This does not seem to be very much to me. This was a saving of 83.00 on my electricity bill. When they came to seel the panels to us the gentleman told me a 2kw system will almost reduce my bill to nothing during the summer months. this is not so. With the month previous to having solar panels my electricity was a very lot cheaper than it is now. Am i set up to optimise and get the most of my panels or is there something else i should be doing

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admin April 27, 2011 at 9:44 am

Hello Rosemary,
In order to help you out specifically, I would need to know the details of your location, both to calculate the the number of Peak Sun Hours (PSH) per day in your location, and the feed-in tariff for your state. Making some assumptions and doing a quick back-of-envelope calculation, however, the amount of savings you described sounds within the bounds of reason but still a bit low. How much was your quarterly bill? (Assuming: 4.5 PSH x 2kw x 84 days x $0.20 = $151) Every system is subject to inefficiencies, and you are also subject to the whims of the weather, which, even if they’re only a few days a month, could take a chunk away from your savings. (E.g.: 15 days without sun x 4.5 PSH x $0.20 = $13.50). Is there anything that might be shading your panels? Even just a small amount of shading can have a significant effect on your system output. I hope you find this reply helpful. Please also see this blog entry about how to troubleshoot a solar power system that is not producing to capacity, which we wrote a while back. Good luck.

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Kieran Lee March 18, 2011 at 5:57 pm

I have 6 kw panels with a 5 kw inverter and my generation is averaging between 32 kwH and 37 kwH per day [except for a couple of very cloudy days] while it has been consistently over 30c and often over 35c right into the evening so I’m not sure if the heat can be to blame (unless this varies on the brand of panel) for Eddie and Adrian’s poor panel performance unless they have had a lot of overcast days. What I have noticed is that for the first month after installation, generation was peaking at close to 5 kw while for the past week or so it is now peaking at closer to 4.5 kw which I am curious about as could conceivably mean a loss of 10% of generation across the day.

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admin March 21, 2011 at 10:41 am

Hi there Kieran,

The losses you are experiencing could well be due to high temperatures in your system. If you can check the operating temperature of your panels and know the ambient (air) temperature around them (this may be hotter than the temperature on the ground, especially if your roof is a dark colour, which it likely is), then you can use this handy tool to calculate what % loss in efficiency you should expect. You’ll also need to know the temperature derating factor for your solar panels, as this may be a bit different from the one on the linked page.

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Eddie March 13, 2011 at 4:45 pm

Adrian,

I’ve also had the same system just installed, and like you have been quite disapointed with the power my 3kw 16 190kw panels and 3kw Aero-Sharp inverter. So far on my best day I’ve only generated 6.9kw which is way below the expected daily average that has been mentioned when reading around the web. My position is also good. I’m going to contact the installer tomorrow and have a chat on what they think i’ll let you know the out-come.

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admin March 18, 2011 at 1:27 pm

Eddie and Adrian,
If you are in hotter, sunnier climes, your problem may be with overheating of your panels–there’s not a lot you can do about this. Generally, STC (standard test conditions) are 25C and 1000W/m2 of sunlight. For every bit that the temperature of your panel goes above that, its rated output is reduced. You should be able to get more info about just how much of a reduction to expect by looking at the specs for your panels, which generally include this type of information. You may attempt to run some water over the panels to test this hypothesis.

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Gordon Gifford March 5, 2011 at 11:19 am

I have a 2.035 kw system 11 x 185w panels and I live in Yeppoon in central Queensland my roof faces north with 24 degree pitch (I am told)
The salesman quoted figures of 6 hours usable sunlight per day giving 12 kw daily.
I have a monitor on the system which tells me what is being produced minute by minute and this does not go above 1600 watts at any time
I was told that the system had an efficiency of 95% which should give 1933 watts
the best daily production I have had is 11 kw does this sound right to you

Regards Gordon

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admin March 18, 2011 at 2:07 pm

Hi Gordon
Thanks for the comment. It sounds like the production you are talking about is in the ball park of what you can expect from your system. What is the operating temperature of the cells? They become less efficient when they heat up, and this may be the cause of your unsatisfactory performance.

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tom March 3, 2011 at 5:09 pm

if i had a wind operated device to run an alternator, could i add this to the solar system. or rather to the inverter

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admin March 18, 2011 at 2:20 pm

A wind power generator would produce AC power. Solar panels produce DC power. An inverter is necessary to turn DC into AC power (which is the type of electricity that the power grid provides.) It is possible to connect a wind power generator into your system–this will most likely be fed into a regulator/inverter, which is a bit different from a standard DC-AC inverter. You couldn’t connect the wiring directly to the photovoltaic part of the wiring.

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Adrian March 3, 2011 at 3:17 pm

I am hoping you can help clarify an issue I am having with my solar panels that I have had reciently installed. It is a 3kw system with 16 panels facing North. I am in SE QLD. I have a 3.6 kw inverter. During the day when I check the inverter it is saying that I am getting 1.8kw an hour when the sun is out and unobstructed. I was expecting the output to be higher. Is this to be expected? The graph peaks after a couple of hours once the sun has come up in the morning and if there is no cloud cover it then levels out at 1.8kw for the remainder of the day before falling back to 0 as the sun goes down. I was expecting it to peak higher at the optimum position of the sun during the day. Im not sure if what is happening is normal or not.

Adrian

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Tom March 2, 2011 at 5:12 pm

Looking to install but looking for a bit of advice first. I live in Perth and have a north facing installation roof with no obstructions. Looking to have 10 x 190w panels with either a 1.9kw or possibly a 2.28 kw inverter. What sort of daily ‘unit’ return should I get with either of those options?

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Pratik March 2, 2011 at 11:21 am

Hi,
Does this mean that we should not buy a larger capacity inverter for the panels, with possible future expansion in mind eg 3 KW inverter for 1.5KW panels?
Pratik

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admin March 21, 2011 at 11:29 am

Hi Pratik,

Thanks for the comment.

The above doesn’t mean that you shouldn’t buy an oversized inverter, but it does mean that you shouldn’t expect optimal performance until you install the rest of your array to fill out your inverter’s extra capacity.

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Julio Bonilla February 25, 2011 at 12:03 pm

Following my previous enquire, I forgot to mentioned that my panels array (8×190 w) is north facing and not shaded at all.
Julio

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admin February 25, 2011 at 1:37 pm

Hi Julio,
Thanks for the comment. How much power is your system producing, then? How far is ‘not even close’ from 1.52kW? Generally, inverters should be oversized by about 10%, but it sounds like yours is over by 50%, so this could be part of your problem. How long are you planning to wait before installing the rest of the system? Your efficiency should improve once you’re operating at the capacity of your inverter.

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Tim Snelson February 19, 2011 at 12:32 am

For several weeks now I have been concerned that my 2.16kw(12 panels) system has not been working to its full capacity, only producing 6.9kw after 12hours of sunshine( I did numerous readings of the inverter to reach that result).Having found your website and read your Average daily production table,it confirms my concern of my system and now I must contact my installer.I thankyou for all your information and the comments from all the other people. Regards Tim.

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admin February 24, 2011 at 1:02 pm

Thanks for the comment, Tim! Good luck with your system.

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Anndrew February 4, 2011 at 5:39 pm

Hi,

I have had a an 1.5KW system put in and commissioned three days ago.
I am in Sydney and have 6 x 240 panels =1440W. The panels are facing North and I have had an average of around 4.5KW being produced per day. 5KW on the sunniest day.

Just wondering is this right? I had assumed that I would get a lot more on a summer day with full sun?

It has been around 40 degrees each day, not sure if this affects the inverter as it has been measuring 52 degrees internal temp.

Thanks Andrew

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admin February 24, 2011 at 1:55 pm

Hi Andrew,
Thanks for the comment. That number doesn’t sound too off the mark, and as noted in the above blog entry, the amount of power produced will vary depending on your circumstances, so it’s a bit tricky to estimate the numbers. Do you get much shading early or late in the day, from trees or nearby buildings? Heat could have something to do with it, as a lot of solar panels are rated for a standard operating temperature of 25 degrees because a lot of manufacturers have cooler climates in mind. You might want to give your installer a call and ask them about it; they should be familiar with the peculiarities of your system. Best of luck!

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Leo January 24, 2011 at 4:37 pm

We just had our solar panel installed last Wednesday and last weekend, I was able to capture the highest generated watts (looking at the LCD display of the inverter). I figured these times are the best time in Blacktown NSW since the sun is directly on top. Note, it was clear sky and hot day 30C+.

Saturday 1:45pm – 2224w
Sunday 1:50 – 2300w

Our system is 2.31kw (11 panels) using SMA 2500.

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John January 15, 2011 at 4:23 pm

Is there a website where I can find out the “Average Daily Energy Generation” or projected average energy production for my town. I understand there will be many factors associated to the results I may achieve. Thanks, John

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admin January 20, 2011 at 2:05 pm

Hi John,
Thanks for the comment. You can check out the insolation (sunlight, generally referred to in the solar power world as ‘peak sun hours’ or PSH) for your area by finding your location on this map, assuming you are in Australia or New Zealand. The amount of power that your system will actually generate depends, of course, on not only your location, but also on the capacity and efficiency of your system and whether there is any shading on your panels from nearby objects (this can adversely affect the output of your system, sometimes seriously.) Check out our FAQ page for more answers to other common questions.

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Rob. January 10, 2011 at 11:58 am

I have been informed that my 2Kw. system(11 panels) connected to 2.5 inverter, can on a good day actually produce more power than 2Kw presumably because I have a larger inverter. Is this the case? Would appreciate your response. Thanks Rob

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admin January 14, 2011 at 1:14 pm

A solar panel system rated at 2kilowatts will on average produce 2kilowatts of power/hour. However occasionally if the temperature of the panels rises due to a greater intensity of sunlight hitting them, this can create a condition where a greater amount of current can be generated. If your inverter is not oversized then this increase will not be noticeable. The inverter does not generate any electricity it merely converts the direct current electricity that it receives into alternative current.

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Rob. January 28, 2011 at 11:04 am

Thanks heaps for that response, I appreciate you taking the time to reply to my query. Regards Rob.

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Wally November 21, 2010 at 12:54 pm

You might be interested in my figures for Sydney:
3kW (12x250W panels) connected 11 Oct 10. Pretty good orientation.
According to the inverter, 490 kWh since then = 11.8 kwh/day
According to the Gross meter, 483 units. Why the difference? Inverter ineficiencies? Metering errors?
Best on a sunny day has been 18 units, worst was 3 on a wet/dark day. Sydney has had a wet Spring, so I expect the figures are below average. And I expect higher figures in Jan at the height of Summer.
Comments?

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admin November 28, 2010 at 5:42 pm

This is very interesting!
The difference could be due to shading, wire losses, lack of sensitivity in the unit from the electricity retailer and as you said inverter efficiency.
The assumption of higher figures in summer is not wrong but it does depend on other factors like ambient temperature and what temperature the modules are rated for.

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Kurt Lehmann July 18, 2010 at 1:34 pm

To work out the electricity output for a 2 kWh system do I just double the figure given above ? For Sydney eg.- 4 kWh per day gives me 8 kWh per day for a 2 kWh system. I would appreciate your reply very much. Thank you.
Kurt

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admin July 19, 2010 at 10:18 am

Yes, that is correct. You multiply the average kWh/day by the size of your system.

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Jo January 26, 2010 at 9:40 pm

Have you guys tested this calculator?
http://solar.anu.edu.au/EduResources/applets/PVPanel/_PVpanel.php

I’ve put some specs in for the basic system I’m purchasing, including upping the number of panels to make a 1.7kW system etc. Admittedly my roof pitch, orientation and location (SE Qld) are pretty ideal, but I got quite high figures (between 5-6 in winter and 10 in summer). Just curious to know if you’ve used this calculator and how accurate you think it is? Cheers, Jo

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admin January 28, 2010 at 10:41 am

Hi Jo,

Thanks for your comment. That is the first time I’ve seen that calculator. It does seem like an interesting application.

When I gave it a run for Brisbane I got figures of 4.7kWh/kWp.day for Summer (1st Jan) and 4.1kWh/kWp.day for Winter (1st June). This isn’t quite as high as the numbers you got (I assume you are in a different location in SE Queensland), however, it is higher then the figures advised by the CEC. The reason for this is that it appears the ANU calculator is measuring the raw output of the PV modules. In reality your PV modules are connected to an inverter and transformer, then wired through a meter and on to the grid. Through all these electrical processes some energy is lost (known as electrical losses, or a DC to AC derrate factor), and the CEC figures take that into account. Another calculator you may like to try is PVWatts (http://rredc.nrel.gov/solar/calculators/PVWATTS/version1/) which takes all of the various losses into account.

Regards,

Kobad Bhavnagri
Solar Energy Consultant
Solar Choice Pty Ltd

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