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# How do I convert KWP of my panel to KWHrs

• 18-06-2022 4:46pm
Registered Users Posts: 2,156 ✭✭✭

I see there is plenty of online calc's but wondering if someone can confirm a simple sum of how to get the output for below based on the normal 1000m2

4KWP system (11no Longi 375W panels) which are approx 1755x1038 so works out approx 1.8mtr per panel

• Registered Users Posts: 2,400 ✭✭✭

The math is both simple and complicated.

Simple as in there's no differential equations, but complicated as while your right that it's a matter of surface area and solar radiation that day......there are many variables at play. Some of which are ..... the temperature of the panels (not the ambient temp), the time of the year.....which affects the "slant angle" that the suns rays are hitting the panels. Are the panels facing due south, or maybe south east/west etc (or some other angle), the slope, the efficiency of the panels (20%, 21% etc)

Basically while in theory it's possible to work it out from the solar radiation, you need to spend a lot of effort doing so.

A better way is to look at the actual KWhr generated for a specific forecast and then average that out over (say) 10 days to get a Kwhr / 1000 solar.

There was a good thread on this...... read it from the start....

Forecasting tomorrow's sunshine (to better use the solar) - Page 4 — boards.ie - Now Ye're Talkin'

• Moderators, Home & Garden Moderators Posts: 5,732 Mod ✭✭✭✭

And also using this for a monthly estimate

https://re.jrc.ec.europa.eu/pvg_tools/en/#PVP

• Registered Users Posts: 10,773 ✭✭✭✭

Okay there's no direct translation of kWp to kWh

kWp is the maximum amount of power your panels will generate at a given time. It's measured under standard test conditions and allows you to compare systems. So a 4kWp system should generate twice the power of a 2kWp system under the same conditions

kWh is the total usable energy generated by the panels over a given time. If a 4kWp system generates 4kW for 1 hour, you've gotten 4kWh. 4kW over 2 hours gives you 8kWh, and 2kW over 2 hours gives you 4kWh

So the only way to figure out the amount of kWh you'll get is using an estimation tool like the one below

https://re.jrc.ec.europa.eu/pvg_tools/en/

"The internet never fails to misremember" - Sebastian Ruiz, aka Frost

• Registered Users Posts: 2,156 ✭✭✭

Thanks everyone, not sure why by not get notifications to my posts so a bit late replying