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I'm interested in installing a solar array on my property, and am trying to find tools that can help me do a cost analysis so I can optimize my budget and see how long it will take to balance the upfront cost.

Are there any tools available to help me with these calculations?

  • 2
    Hi and welcome. At the very least you should specify where you want to install solar panels. It's such a huge difference if you want to install them in Germany, the U.S. or South Africa... – soc1c Jan 30 '13 at 21:28
  • Curious as to the reason for the downvote on this. Does it seem off topic or vauge? – thatmiddleway Jan 30 '13 at 21:33
  • I didn't downvote, but the answer is quite specific to where you live and questions which are 'too localized' tend to get closed. – THelper Jan 31 '13 at 14:35
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    It's OK for this question to be location-agnostic - the laws of physics and economics are pretty consistent worldwide. Prices and government incentives will be local, perhaps too specialized for this site. – Jay Bazuzi Feb 4 '13 at 17:30
  • Unless you want to use it for winter power in Alaska... – user141 Feb 14 '13 at 14:32
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If you are in the U.S. in particular, I would recommend the National Renewable Energy Laboratory's PVWatts calculator, which will provide both likely solar gain (the defaults are reasonable, but you can tweak them to your situation) and potential savings on electricity. For installation costs, again for a US case, LBNL has a great report on installed costs (panels, balance of system, labor, etc.) - the 2011 US-wide average was $6.1/W for small systems (<10kW) Adjust that with local policies and you can get a pretty good ballpark.

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You have to get several numbers:

  • payments

    • how much will you pay to obtain the PV system
    • how much will you pay on taxes, recycling fees from the PV system etc.
  • returns

    • how much will you get back from produced power
    • how much will you save on your electricity bill (price of electricity is rising)
    • how much will you be payed from incentives (if any)

Generally the only (almost) objective answer can be given on how much electricity you can produce. Anything else is subject to change depending on country/location, legislation and on time.

Have a look at my answer. It contains a sample calculation of yearly solar gain too.
Just the explanation: the calculator is based on Europe & Africa data, but those can serve as a rough estimate for any place on the Earth if you keep the right latitude. I'd pick somewhere in Spain as a substitute for Colorado, USA.

After dividing total payments by expected yearly returns you'll get the approximate return time.

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If your want to calculate your own Insolation figures then I would highly recommend having a look at the gaisma website, which provides sunrise, sunset, dusk and dawn times for thousands of locations all over the world.

For our purposes though, it also provides details of average Insolation (kWh/m²/day), along with Clearness, Temperature, Wind speed, Precipitation and Wet days.

For my own location, in Oxford, UK, it provides the following information:

Sun path diagram and Solar energy and surface meteorology Sunrise, sunset, dawn and dusk times graph, Oxford UK

Details of your own location, and prospective PV solar system should allow you to estimate the kWh generated by the system over an average year.

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    -1 as I think the solar irradiance data seems to outdated. You should get better results when using something like PVGIS. – bmu Feb 14 '13 at 10:21
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I think the best tool freely available at the moment is the System Advisor Model (SAM) by the National Renewable Energy Laboratory (NREL) of the US.

For Europe/Afrika a good starting point is PVGIS.

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