Which PV tilt calculator would you recommend?

Hello All!

I am in the process of installing PV on the ground (south facing). I want to align the PV well with the sun to make the best use of the spring / summer / autumn time.
I am looking for a reasonable calculator (preferably open source) that will help me calculate the optimal panel tilt for ~ (52N, 21E).
Can anyone recommend something worth attention?
Thanks in advance for any constructive feedback.

This may help JRC Photovoltaic Geographical Information System (PVGIS) - European Commission

I also found https://pvwatts.nrel.gov/
They show a little difference in results.

That appears to be for the US only. So US (as in UnServiceable) for the rest of the world.

Where’d you see that?

Unless they’re lying to us, their landing page says:
image

and the “about” section says:

:slight_smile: I did not know this abbreviation explanation before.
Nevertheless the site seems to calculate some results for other countries as well.

When I tried to tell it where I lived. I gave it the first 3 characters of my postcode, it showed the map putting me the opposite side of the city to where I live, when I clicked on my true location as instructed, it told me my address wasn’t in the US. Which is true, it isn’t.

image

The other website mentioned earlier worked fine for me, and appeared to be credible.

If you give it Birmingham UK vice your post code, you get this:

Resource Data Map

The blue rectangle on the map indicates the NREL National Solar Radiation Database (NSRDB) grid cell for your location. If you want to use data for a different NSRDB grid cell, double-click the map to move the rectangle. Dragging the rectangle will not move it.
If your location is outside the NSRDB area, the map shows pins for the nearest alternate data sites instead of a rectangle: Click a pin to choose the site you want to use.

Using the “defaults” for each calculator, I got:

PVWatts:



PVGIS:

A difference of 139 kWh over the span of one year.