### Author Topic: Calculating peak sun hours using historic data  (Read 250 times)

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#### flainn

• Member
• Posts: 27
##### Calculating peak sun hours using historic data
« on: July 15, 2020, 03:21:59 PM »
Hello,

I'm thinking of installing a solar electric system on my house, and am in the planning phases. One of the things that you use in planning these systems is "peak sun hours per day" for your location -- the number of average hours each day during which the sun is shining at 100% of maximum for a given location.

You can look up these values for a nearby city (in my case, the closest is Albuquerque, 6.77 peak sun hours per day or 6.77 kWh/m^2/day), but I've been running a Davis Vantage Pro 2 at my location (with a watt meter and a UV sensor) for about fifteen months now, collecting the data with WeeWX, so I should have pretty reliable data by now. But I don't know how to turn the wattage data (instantaneous watts per meter) into what I need, which is KWh / m^2 / day. Probably it's possible with a lot of math and/or a spreadsheet, but I was wondering if perhaps WeeWX has some built-in method.

This isn't at all critical to have, but it should be more accurate than Albuquerque's data (Albuquerque being about 70 straight-line miles north of me). Thanks!

#### Storm017

• Contributor
• Posts: 125
##### Re: Calculating peak sun hours using historic data
« Reply #1 on: July 15, 2020, 04:43:24 PM »
Might want to ask the question over on the weewx user group: https://groups.google.com/forum/?oldui=1#!forum/weewx-user

#### flainn

• Member
• Posts: 27
##### Re: Calculating peak sun hours using historic data
« Reply #2 on: July 21, 2020, 10:50:28 AM »
I've posted it to the WeeWX group on Google Groups. Thanks for the suggestion.