What country should use solar power or has the ability to use a lot of solar power but?

Saudi Arabia, Iraq, Iran, Egypt, Libya, Morroco, in fact most of Africa, Australia………..

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Any desert country.

All countries can make use of solar power. The extent to which they can do this is determined by the weather. If you are looking for a market, try any country that has a desert.

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Right now, you're looking at any nation on Earth. Any roof without a solar panel is a waste of potential energy. If you're looking for the nations which will gather the most energy, you'll want nations with lots of sun and lots of land area (count England out, for example)… but more importantly in marketing is finding a nation where the government or powerful people care about the environment and have the money to spend.

anywhere in the Arabian peninsula, but why would they bother, they have enough oil

you know how many people are clueless about solar in the u.s.?