Solar capacity factors averaged 15 per cent globally in 2025, according to Thunder Said Energy, with a wide variation in the efficiency of solar by region.

An efficiency of 15 per cent would equate to 1MW of AC solar capacity generating 1MW x 24 hrs/day x 365 days/yr x 15 per cent, which works out at 1,315 MWh per year.

This clearly matters for solar economics. At one side of the spectrum, Germany is one of the least sunny countries in the world, with around 1WWh/m2/year of insolation, supporting a 12 per cent capacity factor. The UK is slightly higher.

On the other side of the spectrum, the Atacama Desert, in Chile, is one of the world's sunniest locations, receiving 2.6MWh/m2/year of insolation, supporting a 30 per cent capacity factor, and a lot more seasonal stability. This stability lowers the cost of a round-the-clock solar and batteries combination. Numbers are similarly high and stable in the heart of the Saudi Arabian desert.

Real-world solar installations tend to fall short of these potential capacity factors by 0-5 per cent, due to tracking error, pollution and grid issues.

Which makes for interesting economic decision, over whether to invest in transmission or production, and which renewable option is best for any country.

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