Solar energy and other forms of renewable energy (such as geothermal) are a good investment?

If you're referring to your portfolio, probably not. The industry is new, and failure rates in new industries are atmospheric, as has always been the case. Look at the Edsel or the Tucker in the auto industry. Great cars but lousy companies.

If you're referring to your personal life, then intangibles come into play. Would you prefer to spend less on electric bills? Would you prefer to have electricity after a big storm? Would you like to mainstream the new industry so that you can include it in your portfolio?

Most have a very low Rate of Return, and others fail. So really not a great profit center. Often the cost is high for personal use start up, but good for personal use.

It also depends on where you live, how much sun you get, for solar. Heat pumps and such are very expensive. There are high start costs, so how long you plan to live there is important. In the US, there are tax credits, depending on where you live. For an existing house, the angle of the roof and orientation to the sun might be wrong, so you have to put them on the ground. There are problems for firemen if there is a fire.

Much too general a question!

California, New Mexico, Arizona, Nevada, possibly Florida are good PERSONAL solar investment if you consider the "feel good" factor. From a portfolio investment, not so good and with oil falling even lower, it makes solar and wind less competitive. Gas right now near my house is $2.19 or less .

Thanks Guys for your awesome answer