[N]ot-very-glamorous changes like [compact fluorescents lightbulbs] as well as obsessively sealing and insulating your home will save more than, in the words of one expert, “greenie weenie” additions like green roofs and solar panels.
The whole article is worth reading. But in case you’re too busy, here’s the point in a nutshell: if you really want to reduce the environmental impact of your home, do all the simple, boring things first. Seal up holes with caulk, insulate, and buy efficient lights and appliances. It’s not sexy, it’s not trendy, but it’s important.
Once you’re done with all the boring (but cost effective) stuff, you can think about the nifty high-tech energy solutions, like solar panels. (Or, perhaps you’ll do even more good by helping your neighbors do the simple stuff, too.)