That diagram suggests Northern Sweden to Southern Europe is 50%, not 80%, which sounds more plausible.

Thanks! That is quite surprising, and very encouraging.

It seems that solar is a very good overall fit for even most of the world, and once the tech is good enough to be used in huge numbers the differences can probably be compensated with other, local power sources (like hydro in Scandinavia, which is huge there).

> What people miss is that during the summer the sun is up all the time. (In the winter, not so much.)

It sounds like these two effects should cancel each other out. Are you saying that people take winter into account but not summer?

Depends on what you're using it for. A common use-case is cottages that run off the grid, which are only used in the summer half of the year anyway.

But cold panels produce more power.

PVGIS is an excellent tool and I have been using it for years!

Do I understand correctly that the wishful thinking value of 75% photovoltaic conversion efficiency is plotted in the diagram?

It means the conversion factor of yearly yield in kWh to installed PV in kWp. "Yearly sum of solar electricity generated by 1 kWp system". It's not about the physical PV efficiency.

The 75% performance ratio represents system losses not module efficiency. So a system rated at 1kW(peak) which may be 5-6 square meters in size, and which is exposed to annual sunlight of 1200 kWh/m2 might only produce 900 kWh of usable power.

So efficiency has to do with the rated power per surface area and the performance ratio reflects all the system electrical and environmental factors that reduce the amount of usable power below what would be expected based upon module ratings and annual sunlight exposure.