I did this! Well, I and a small team. google.com/sunroof It even does the integral over every pixel of your roof, so as to take into account shading from nearby trees and houses (as well as non-flat roofs, horizon effects, chimneys and other roof obstructions, ...). You might also like NREL's PVWatts calculator <https://pvwatts.nrel.gov/>, which is less accurate (because it doesn't do the full ray-tracing over the roof thing) but provides more intermediate information. -Thomas C On Mon, Jun 29, 2020 at 10:52 AM Henry Baker <hbaker1@pipeline.com> wrote:

I'm considering putting a solar PV system on my roof, and I thought that I should be able to calculate most of the numbers myself from first principles. I have searched for so-called online 'calculators', but found that most of them are aimed at idiots.

Here's what I expected to find:

A formula giving the exact sun position throughout the year, given latitude and longitude, as well as a factor which handles the distance from the sun w.r.t. time.

Now this only provides the *input* energy.

I now need to overlay this with average *weather* data on a per-hour basis to get the expected net energy.

Finally, I need to *integrate* these data over an entire year to get the values for my own house.

There may be such an online calculator, but I haven't been able to find it yet.

It may be possible to factor the weather info out of the integration, so that I could 'correct' my location sunlight & weather data with my own lat/lon azimuth (angle of my house) and roof angle, but I'd need to see the equations to find out if this factoring is possible.

I presume that someone on this list has already done these calculations for their own home?

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