I've been a fan of solar for decades, it's free energy that just falls on everything we own. It's almost literally like cash raining from the sky, and we mostly just sweep it up and throw it in the trash without using it. A square meter can have just over a thousand Watts of energy falling onto it under really good conditions, and even up here away from the equator it's pretty easy to catch 500-700 Watts with a square meter of PV. Solar water heating is even more cost-effective, and in fact, before the advent of natural gas pipeline distribution systems solar water heating was very popular and growing quickly.
Lots of info in this well-researched book:
Did you know people were using solar heating principles four thousand years ago? If I were to recommend just one book on the subject of solar energy, I'd recommend this one.