It depends where you live, as "green energy" typically tends to make the most efficient use of its immediate environment. For example, hydroelectric power is very useful is you live near oceans, rivers, or other dynamic water sources (a lake, being typically static, is not a good source of hydroelectric power). And if you live in a windy valley, then wind-powered turbine generators make the most sense. If you live in sunny California like me, solar panels are great, because we get so much natural light! But I think, as a general rule, it's safe to say that investing in some solar panels is the overall best value. They are expensive at first, especially if you pay someone to install them for you, but they are very consistent and effective at converting solar energy into usable power. They will pay themselves off in the long run, and don't come with the high labor and maintenance costs of wind or water power.