What solar panel sizes should you buy?

Comments

1. Hi, we live in the Adelaide hills and have 2 phase power to our house and shed. Would it be possible to feed back into the grid with a solar system, or would the 2 phase present a problem? Thanks for any information

2. Hi I currently have a 5kw system I would like to upgrade to a larger system I am on single phase power. Could I upgrade to a 10kw system?

3. Elon Musk was recently quoted as saying that his batteries may cost as little as US$100 per kwh by the year 2020.
   If this actually happens, it seems to change all the economics of solar PV.

   We’re planning to build next year, and I’m wondering whether is it possible to buy a solar PV system which would have the option of retro fitting a battery later without any significant extra expense ( for example just buying the battery and getting an electrician to connect it up.)

   If this is an option, it might make sense to get a larger system than what is recommended. Both before and after a battery was connected we would want to feed any surplus production into the grid.

   1. Hi Mike,

      It’s possible to get a ‘battery ready’ system installed – usually fitted out with a ‘hybrid inverter‘. That being said, it may also be possible to retrofit batteries onto your existing system when you’re ready even without a hybrid inverter.

      Battery storage is already on the cusp of making pure economic sense, although it may be a few more years before it’s a ‘no brainer’ for solar homes to install batteries.

      Another approach you could take would be to install an Enphase or SolarEdge system (microinverter and power optimisers, respectively). While these technologies may be a bit more expensive at first, they both have the attractive advantages of being a) easy to add additional panels onto and b) battery-friendly. This means that you won’t need to install all the extra solar capacity beforehand (as you might with a conventional system with a string inverter). The other upside is that both of these systems can potentially help you figure out how much battery storage capacity would best suit your needs once you’re ready to install your batteries.

      You could consider installing just a small amount of battery capacity to get started as well. Enphase’s AC Battery is perfect for this kind of situation because each unit is small and modular – you can install as many or as few as you like.

      Hope this helps.

4. hello Sir / Madam please i have an internet cafe in Ghana and we are having power crisis here in Ghana and you such business need power to run.
   so i decided to go for solar energy so i want to know how much will it cause me .
   10 computers
   1 printer
   1 scanner
   air condition
   TV set
   6 bulbs
   2 fans but wither i will use fan or AC
   how much will be am from Ghana in west Africa

   1. Hi Edward,

      Unfortunately we operate only in Australia so can’t help you out directly. As a rough guide, a system between 10-20kW might do the job for you, but you’ll want to do the math yourself (how much electricity does each of the devices you mentioned actually consume)? Additionally, if you’re not going to be connected to the grid and will be operating at night, you’ll also need batteries.

      Hope this helps, and best of luck to you!

5. Hello,
   What impact does solar power have on off peak floor heating. Can the power be stored for night time hours? Advice so far has been confusing and different depending on installers.

   Wendy

   1. Hi Wendy,

      The way solar works right now (if you have no battery storage) is that you need to consume the solar energy as your panels produce it – that means that if you don’t use your floor heating during daylight hours, having solar panels is not likely to help you save a lot of money on your bills with regard to floor heating.

      Then again, we are not floor heating experts here – once the floor is warm, does it stay warm for a long time without further energy input? If that’s the case, then you could theoretically pre-warm your floors using daytime sunshine so that they’re warm for when you come home in the evening.

      Hope this helps.

6. Interested Papua New Guinea with solarpower since Iam a mother unemployed and doing market. I loved solar power which cut cost for all the electrical powerbilling, my interest is for a 1kv power will best suite my need.

   1. Hi Nora,

      Unfortunately we only service Australia at this point in time. It sounds like you are after a small number of panels – perhaps you could source the panels yourself online and then get in touch with a local electrician to install them?

      Best of luck!

7. Hi,
   I have installed a 3 Kw Delta inverter with 12 panels @250w 6 months ago and I’m not happy with efficiency of the system . During the day there is no one at home and everything is switched off apart of refrigerator. I’ve tough that Ill be able to half my power bill but for 94 days my system harvested only 187kw. Is there anyone that can check the system and improve its efficiency?
   Thank you.
   Robert

   1. Hi Robert.

      Your system should be producing around 8-10.5kWh per day–by my calculations based on the figures you gave (assuming that by 187kW, you meant 187kWh), it’s only generating about 2kWh/day. Something is clearly not right with the system. I would recommend that you get in touch with the company that installed your system–they would be the first port of call.

      As far as what could be causing the problems–is there anything that casts shadows on any part of the solar panel array?

      It’s also important to know where you are and whether or not you are signed up for a feed-in tariff incentive. If you do not have a feed-in tariff you should be endeavouring to consume as much of the power as possible yourself during the daytime. Where are you located?

      Good luck with your system.

   2. make sure all the panel blocks s are switched on, when my system was installed they forgot to switch one block on so I climbed on the roof and switched it on myself

8. Hi,
   When the solar PV is installed how, what, when and more importantly who buys the excess energy. If I am currently with an electricity supplier do I stay with them and ask them to buy my excess? How does this part of the arrangement work out?

   1. Hi Karen,

      You don’t have to stay with your current installer, in fact, as a resident of NSW it’s worth your while to shop around. We have have a number of installers on our network who work with niche energy retailers, these retailers give solar PV customers a much better deal on the energy they feed back to the grid than some of the bigger names in the business. I can see you filled in our quote comparison form, someone will be in contact with you shortly to discuss your project – feel free to quiz them on anything you want to know!

   2. hi,in nsw click energy offer 10c a kwh for excess energy after home useage with a net meter system

9. HI , I have installed a 1.5 kw inverter with 8 , 190kw panels and am very happy, so I want to upgrade to a 3kw inverter. Will I need more panels? Thanks, Lester.

   1. Hi Lester,

      You currently have 1.2kW worth of solar panels with a 1.5kW inverter. I’m glad to hear this is working out for you. However, upgrading to a 3kW inverter would not be a wise idea at all unless you are planning on at least doubling the size of your solar panel array–i.e. 2.4kW, preferably more. 3kW inverters function optimally when there is 3kW of solar power flowing into them. Generally speaking, the further the gap between inverter and solar panel array capacity, the greater the efficiency loss. Read more about solar inverter efficiency.

10. I regret having solar power panels installed.When the companys are trumping up business they make it sound so good. If I invested my hard earned $’s I would be far aheadI feel we have just wasted $12,000. The salespeople don’t explain enough. We had advice from several avenues before deciding to have 3 kw system installed.
    I guess the goverment or electricity company will lower the rates for the buy back soon and one will be further behind. The way we are going it will take us 20 years to get back our money at $1 per day Ha!!

    1. Hello Pauline,

       Sorry to hear that your system’s performance is not meeting your expectations.

       I’ll need to ask a few questions to assist in troubleshooting:

       -When are you using your electricity? If you are using electricity during the day when the sun is shining and your system is producing power, you will not see any credits on your bill because you are using the power directly. This means you are saving money from avoiding the need to purchase electricity from your electricity retailer in the first place.

       -How much electricity (in kilowatt-hours or kWh) is your system producing on average? You should be able to find this out by looking at either your electricity meter, or on your monitoring equipment (via your inverter) if you have one. A 3kW system in central Queensland should produce approximately 12kWh per day.

    2. hi pauline, I`m onto my second home with a 40 panel 10 kwh system, 1st one installed 3 years ago cost $13900. complete and generated up to 70-73 kwh per day, latest one installed a month ago same size only cost a bit over $9000 including metering and is generating up 73 kwh daily, 1st home returned up to $13000 a year from the solar buy back at 60c kwh, current one is net metered with 10c kwh buy back for excess after home useage, these system are getting cheaper all the time and I will put in a battery system as soon as they are cheap enough,

       1. Hi Brian
          I am interested to chat with you about what brands and company u have used . I am wanting a 10kw system and looking at doing this very soon. Same as you re the batteries.
          I have come across a company called Alpha-ESS and they look really appealing and have spoken today with a retailer for this system. Have you heard of it ?? Solar panels and battery.

11. The comments at the top of the page are not quite correct! If the average daily usage is 12 -16 kw hrs per day not ALL of that consumption is in daylight hours?? You can only generate electricity while the sun is up! You first need to asses what the avge daytime consumption is before you can work out the size of the system you need??

    1. Hi Chris,

       Thanks for the comment. The comments at the top of the article refer to a situation where the owner of the installed system lives in a state with a Solar Feed-in Tariff or 1-for-1 Solar Buyback. Provided one of these 2 schemes is in place, the time that the solar electricity is used is not important.

       You would be correct, however, if you were thinking a state where no Solar Feed-in incentive scheme exists. In NSW and most of WA, for example, it only makes sense to install a solar system if you are planning on using the power during daylight hours.

12. what happens if you get the Q.L.D government solar panel grant and you sell the house

    1. Hi Marley,

       The Queensland Solar Bonus Scheme Feed-in Tariff is available to both those who install a new system as well as those who operate existing systems. This means that if you sell your home, the following owner will be eligible to receive the Feed-in Tariff.

13. hey can u plz help me out with a few of my questions
    1- for producing 1kw of electricity what should be the size(area/dimensions) of solar panel?
    2- how to calculate efficiency of solar panel? and when i know the efficiency,how to calculate the area of solar panel? and therefore how to calculate its cost?

    1. Hi Swapnil,

       Thank you for the questions.

       1. The area that your solar panels will take up depends on the efficiency of the the solar panel brand and model that you have installed. For example, if you went with Suntech Ad+ (190W) solar panels (a fairly standard panel for Australia), you would need about 6 panels to make assemble a system that is a little bit more than 1kW (it is impossible to get exactly 1kW). The solar array would take up about 7.6 square meters on your roof if you lay them flat (the best option), but possibly more if you have to/want to tilt them at an angle for greater efficiency (because you then need to be careful that the panels don’t shade one another.)

       2. Different solar panels have different rated efficiencies, so you don’t need to calculate the efficiency of the panels themselves. For example, the efficiency of the SunTech modules I mentioned above is 14.9%. This means that the panel can use 14.9% of the sunlight that falls on the panel. If the efficiency is lower, if means that the panel can not use as much sunlight. In effect, the biggest difference with regard to the efficiency of a solar panel is the amount of space that it takes on your roof. Less efficient panels need more space.

       Please remember that the solar panels are not the only part of the system, and the efficiency of the panels is not the only part of efficiency of a system. You also need to think about the inverter, the orientation and tilt angle of the panels, the wiring, and any possible shading that might happen as a result of nearby trees.

       A Solar Choice broker can help you to decide what size of system would be best for your home and energy usage. Please fill out our form to get a comparison of solar quotes from installers in your area of Australia, or give us a call on 1300 78 72 73.

14. Exploring Solar Panel Installation costs

    1. Hello David,

       We’d be happy to help you out. Please give us a ring on 1300 78 72 73 or fill out an online quote comparison request here.

15. just startig out on investigating solar power

16. good

17. Thanks for info. We are in NSW, and own our own home. We are thinking of putting in solar. However, we are moving overseas mid next year, and renting our house while we are away. Is there a way to credit the electricity our panels will produce to us, while our tenants pay for the electricity they use?

    1. Not that we have heard of.

18. thankyou so much for all this information. it has been very hard to find any, anywhere else. just wanting to know though how to decide which company to use? other than by price how do you find out who is reputable and who is not. everyone says they are and no one else is, off course.

19. Hi, I’m on OFFPEAK Hotwater currently. How would that fit in with a,say, 1.5kwh System? Is it all under that ‘one’ System or would there also be Domestic/offpeak? Thank you, Werner

    1. You would simply get paid the Feed-in-Tariff (FiT) rate for your state for the amount of electricity that you generate (or generation minus consumption if you live in a net-FiT state).

20. Hi, we are going to build a 3 bedroom cottage at Palana, Flinders Island, House roof dimensions 17m x 8.5. Tasmania. We are a retired couple, Could you please help us in determining an estimate of installing a system that would also feed electricity back into the system. We are connected to the grid. Also, can you assist us in what currently is the situation as to how much is paid to us in feeding the ‘over-load’ and as to what rebates are available (federal and tasmanian state). Thank you

    Carita Bathman

    1. Hi Carita,

       Wow. Sorry for the very delayed reply. I hope we’ve already been in touch with you. For a price quote comparison, please see this page:
       http://www.solarchoice.net.au/request-quote-comparison.php

       Thanks!

21. What happens in a blackout? These are common in my region (1-2 times pA). During the day, when a 2kW system is producing 8-10kWhrs, it may cover the household use – but it may not. Can I wire my house so ‘essential’ services (fridges, TVs) are fed? If not, where does my unused power go? Obviously, no benefit at night.

    1. Usually the inverter will shut down and the power being generated by your panel will be wasted, unless you have a battery to store the energy and direct it to your house-hold essentials. Thus, if blackouts are common in your area then you might want to consider a battery pack sized for your essentials during the night when the sun is not shining. And yes, we can help you in refining your criterion and connecting you with an appropriate installer.

22. Hi,
    The author has done a great work. I appreciate his work.I am highly oblige for this because it helps me a lot.

23. It doesn’t appear that there are any rebates if the system is installed in a holiday house. Is this correct?

    1. Hi Allan,

       No this is not correct, except if you are a Victorian. All of the standard rebates including the REC solar credits and feed-in tariff are completely eligible for a holiday house in NSW, Qld and SA. Infact, there are substantial benefits to installing solar panels on your holiday home, particularly if you live in Qld or SA. For an indepth discussion of this, please see our article; Putting solar cells on your holiday home – a nice little earner.

       In Victoria, however, holiday homes are not eligible for the Victorian Government solar feed in tariff, although installations will still recieve the REC bonus and the market rate of electricity. Assuming you are a Victorian, thanks for pointing this out. I’ve made a correction to our post.

       Here are the relevant quotations and links on this matter:
       REC solar credits (applies nationally): No reference is made to occupying or residing at the premise, nor to holiday homes. See Definition of and eligible premises in SGU owners guide.
       NSW: eligible premises must be “owned or occupied”, not owned and occupied. See FAQ answer; Can I install a solar photovoltaic (PV) system or wind turbine up to 10 kilowatts on a neighbour’s roof and receive a credit under the Solar Bonus Scheme?

       Victoria: “The premium solar feed-in tariff cannot be claimed for holiday homes”. See FAQ answer; Who is eligible for the premium rate?

       Queensland: No reference is made to occupying or residing at the premise, nor to holiday homes. See FAQ answer; Who is eligible to receive the bonus?

       South Australia: No reference is made to occupying or residing at the premise, nor to holiday homes. See FAQ answer; Who is eligible?

       Kobad Bhavnagri
       Solar Energy Consultant
       Solar Choice Pty Ltd

24. We are moving to Northern NSW near Yamba, this year to build a new house. We would like to put in solar with the right amount of panels for a family of 5 max at any one time. House will be approx 28 sqs physical rooms and 35 under rooflines in brick/rock/glass/tile roof. We would like to know what to look into NOW, – blogs, websites, feedback etc for the best solar system in NSW so we can choose the right system for us and build it with the house. Anyone have any ideas where to start. I am very ignorant of the workings of this at this time but intend to be fully informed. Please feel free to email us. Thanks

    1. Start by building with blocks, sand in all openings of the blocks. PUT INSULATION on the OUTSIDE 2 INCH OR MORE SOLD FOAM, concrete floors with as much tile as you can, porches over as many of your openings as possible. Use high rated windows and doors installed with foam and foam in ever crack inside and out. The more overhang of the roof you have the better. Look at concrete home building systems. By doing this your home becomes a huge icebox with the heat and cold STORED INSIDE, IN ALL THE CONCRETE.

       1. Hi Rick,

          Good points. We often point out that the first step in ensuring you’re getting the best out of your solar PV system is to make sure that your home energy use is as low as possible, which means utilise passive solar design techniques (such as insulation and thermal mass in concrete as you’ve described), and then use your electricity wisely–don’t squander it.

25. We are moving to Northern NSW near Yamba, this year to build a new house. We would like to put in solar with the right amount of panels for a family of 5 max at any one time. House will be approx 30 sqs in brick/rock/glass/tile roof. We would like to know what to look into NOW, – blogs, websites, feedback etc for the best solar system in NSW so we can choose the right system for us and build it with the house. Anyone have any ideas where to start. I am very ignorant of the workings of this at this time but intend to be fully informed.

    1. Hi Claire,

       We are also in the same boat – moving to north coast in a couple months and wish to put solar on our house before we get there. Would be interested in any information you receive.

       1. You can get the same information tailored to your interests if you can fill out the short form in the link below.

          Click Here

26. So just how reliable are these systems (inverter and PV panels) ?
    Do you have to purchase the meter from the power company or is it part of the install ?
    Do you have to climb on the roof and wash the panels or they become less efficent with age due to dis-coloration.
    Can you get adjusting panels to accomodate the lower angle of the winter sun

    1. Hi Greg. The minimum standard for reliability is established by the Clean Energy Council and the BCSE accreditations, which all installers on the Solar Choice network maintain and abide by. This ensures the proper international standards for construction of the panels and inverters has been verified, and they have been tested to various temperature, weather and output controls. 25 operational warranties exist on the panels and 5 year operational warranties on the inverters. Manufacturers warranties differ from installer to installer, but are a good standard to test various quotes by.

       The meter must be purchased from the power company as the costs and arrangements differ based on the supplier, and a level 2 qualified electrician needs to carry out the work.

       The panels do require a wash down occasionally, depending of course on how much dust/salt build-up they are exposed to. In reality a strong enough downpour of rain will carry out this work for you.

       Here is an article on various types of solar tracking, including the adjustable tilt frames you’ve mentioned: http://www.solarchoice.net.au/blog/solar-trackers.html

27. I’d love to hear comments from someone who has actually had the solar electricity panels installed.

    1. Hi Gerald.
       I’m currently exploring the grid-connect thing and am running across hidden pitfalls.. eg. The chit-chat about the feed-in discount, etc. sounds good, but they DON’T tell you that it only relates to the unit-price of electricity, and does NOT count the the ‘service charge’, which has just gone up about 14% and is set to double in the next 18 months. (I’m currently paying about as much for the service charge as for the power!) And there’s no accounting for the GST component.

       I mention all this because I lived with solar (and later also hydro) power from 1982 to 2001, and gained a LOT of experience.

       GETTING the power is relatively easy; the problem lies in the storage. Batteries and their maintenance are always a nuisance, though I must say part of my problems were due to using old traction batteries from the tip. (free!) A friend of mine who bought proper (though second-hand) deep-cycle batteries replaced them recently after 26 (mostly trouble-free) years. She’s also using my old panels (second-hand in 1982 for $6 per watt), and they’re still producing just over 85% of their rated power!

       If you can afford to commercially grid-connect, you can afford top-shelf INDUSTRIAL deep-cycle batteries like the ones used in forklifts, etc, which should last forever. And if you keep your system under 50 volts (ie: panels NOT connected in series as per grid -connect) then you can do it all yourself instead paying some rip-off merchant inflated prices for the donkey-work.

       And unless I get a much better deal than I’ve been hearing that’s the way I’ll go, and bugger the FIT. Instead of paying up to $14 per watt, you can buy panels (eg ebay ~ but you need to be careful) for as little as $2 per watt. I’ve done the arithmetic, and reckon I can set up a stand-alone 3kw system (in Victoria) for about $7500 to $8000.

       There are many other hints and innovations that make such a system more practical, and you’re welcome to contact me if you want to discuss them.

    2. If you are off the grid and install batteries and inverter to store and convert you power to 220V then it can become expensive and ” not so green” Battery technology and storage is still not highly efficient so if you have the ability to feed into and extract from the grid it seems to me that is the most efficient way to do it while we wait for storage capacities to improve.

       1. Hi Bailes,

          At the moment the economics of energy storage do not stack up for most people, but things are changing quickly. We will be keeping an eye on the changing technologies and reporting on them here in our blog.

28. The thing that really annoys me is the fact that we are still connected to a grid. Why are people not realising that you have the potential to produce all your own electricity and not be a slave to the power companies. They say that producing green energy is more expensive and hence the consumer must pay more. So all that green energy that gets pumped into the grid is charged to other consumers at what rate exactly? Want to save the planet? Then break free from corporate greed

29. Helen,

    Just to expand slightly on Glen’s comment, a solar energy system doesn’t provide your house with electricity. It simply adds electricity on to the grid you are connected to. You will still be using energy from the grid if you have a solar energy system installed, but the amount of energy your panels generates is measured at your meter box and minused from your bills.

    When you are generating more than you are using, your meter winds backwards, and you are compensated at a premium rate in most states for this. This is known as the feed-in reward rate.

30. Val,

    The short answer is no. Any increase in market rates for electricity will result in proportional increases in the feed-in reward rate. The main benefits for a stand-alone system are if the costs of connecting to the grid is prohibitive or if you need a back up battery system in times of blackout.

31. @Helen
    Hi Helen,
    I can help you with this one, “Since the solar panel don’t work in darkness and they don’t store the energy itself, then what energy are we using at night?”
    On a grid feed system, your electricity is taken as per normal from the grid. Your new electricity meter that is installed, winds back when you are generating electricity and goes forward when you are using electricity.

32. Since the solar panel don’t work in darkness and they don’t store the energy itself, then what energy are we using at night?

    1. Helen,

       you are using power from the grid at night, unless you have a batter pack in which case it is the power from the solar panel.

33. If one is to install a solar system now. Will the providers up your rate because they are loosing revenue? Or disguise it as a new rate rise to think one is saving something which gives a false saving? This may occur unless we are self certificant.

34. No one is telling the potential worth in dollars of the Feed in Tariff to thr Victorian Grid. Will it be capped at a value of $600 p.a.for systems less than 3.2 k.w.h. Some adverts say you could save $180 p.a. with a 1kw solar panel array (power into your house). Would you then add the two figures for a maximum annual saving, potentially $780p.a.? What is the math on what you can earn/save, please.

    1. David,

       A 1kW solar panel system produces on average 4-5kW hours per day. A 3.2kW solar power system would produce approx 14.4kW hours per day.

       To calculate how much a solar energy system will earn you in real terms/$, imagine you were away overseas for a year, and all appliances in your home are turned off. For a 3.2kW system, 365 days x 14.4kW hours is 5,256kW hours. Victoria’s solar feed in tariff rewards you at 60c per kW hour. So 60c x 5,256 works out at $3,153.60 per year.

       That is the maximum amount a 3.2kW solar energy system can earn for you with the solar feed in tariff in Victoria, and for 1kW the figure would be $1,051.20. How much you actually earn depends on how much energy you take from the grid, and of course there is a great variance in individual energy use. Have a look at your energy bill and work backwards from these figures.

       Your new bi-directional meter keeps a tally every 30mins on whether your solar panels are producing more energy than you are drawing from the grid. If you come out ahead for that 30min period, you are rewarded at the premium rate of 60c per kWhour for that surplus amount only. So the more you can maximise the amount you are ahead during daylight hours by running an energy efficient home, the more your panels will reduce your bill and earn you credit.

35. Thanks … very helpful!

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