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Historic solar data

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March ended up being a better solar month than April, which was surprising as we have more shading and snow in March. Is there a website that I can look up what average monthly sun was by zip for a particular month, or a site that lists nearby PV systems with their monthly production numbers?
 
This came up before, and I found (but did not use) Solcast - Solar Forecasting & Solar Irradiance Data - it has an API and free registration for individual homeowners. It may give you the history (as well as forecasts.)

Also Home - NSRDB - this is the data used for PVWatts. However (also not having used it) I am not certain how quickly it adds historical data.

Interestingly, for here, April was the best month I've had so far by a good margin (with August being my first full month on grid, so not a full year) - the first to actually beat PVWatts. March was good (matching PVWatts) after February was terrible.
 
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March ended up being a better solar month than April, which was surprising as we have more shading and snow in March. Is there a website that I can look up what average monthly sun was by zip for a particular month, or a site that lists nearby PV systems with their monthly production numbers?

pvwatts should for past dates should be historical.

That said, my production numbers have far exceeded pvwatts estimate and Teslas estimate of what it should produce.
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For historic output from nearby solar systems, pvoutput.org has a map that you can locate installs near a particular area, and if you like can match details like size or orientation to best approximate your own - daily, hourly, 5-minute data is available if the contributor logged the granularity. Going back more than a month, you do have to log in to see the historic data - I think a free account would suffice, but not 100% sure, since I use a $10/yr paid account to upload my own data.

Alternatively, you can search the Enphase map of public systems

Enphase US Map

and view historic daily and hourly generation data as well. All are Enphase micro-inverter systems though.

For historic solar radiation data, you can search Personal Weather Stations (PWS) in wunderground.com that upload near you, and find the rare one that has a solar sensor, and it will give you historic data from past days. I see in the daily view the irradiation graph over the day, but not sure if they summarize the total daily irradiation under the curve or not for you.
 
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