I have seen number as low as $200\ \text{W}/\text{m}^2$ to $1000 \text{W}/\text{m}^2$.

I'm in California and looking for information on how much power my solar panels will pick up.

I have $4100\ \text{W}$ panels.

I can get the efficiency of the panels from the manufacturer but I need to know what I'm starting with.

Assume a clear day. Obviously it will vary with the date ( distance from the sun ) and geographical location ( same ), assume California.

Assume I am at ground level. Any kind of graph / chart would be useful.

I was boggled at all the stuff Google pulled up that was not relevant for someone trying to do simple ground level calculations for a few solar panels.

These guys state $1000\ \text{W}/\text{m}^2$

These guys state $300\text{W}/\text{m}^2$ to $600\text{W}/\text{m}^2$ depending upon location and weather.

Given a clear day and no other information (location, season, etc.), should I assume $500\text{W}/\text{m}^2$?

Probably best to get a meter and just measure it.

These guys state $1000\ \text{W}/\text{m}^2$

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    $\begingroup$ This is both very latitude-dependent (i.e. more sensitive than "assume California", which spans 10 degrees of latitude) and very weather-dependent, which is why you see such variation. $\endgroup$ – probably_someone Dec 5 '18 at 1:42
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    $\begingroup$ You might get the most useful feeling of it at your exact location by Googling for a a solar irradiance map of the planet or of your continent. $\endgroup$ – Steeven Dec 5 '18 at 8:28

The most basic answer is 1000 W/m^2. The reason you see lower values is that they are covered by cloud, etc.

But the question you really want to ask is "how can I calculate how much power my panels will produce?"

The answer is "you use this calculator". Just follow the prompts and you'll get everything you need, including average insolation.


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