Another factor to consider in "going green" is how much impact you'll have by switching to solar or another renewable energy source.
I've long dreamed of running my office on solar power (I work as an environmental writer and editor, so it's a natural for me and a selling point for my services), but where I live nearly all our electricity comes from hydropower and thus produces no greenhouse gas emissions or conventional air pollutants. In my case, switching to solar would have pretty much zero benefit to the environment, and the cost of electricity here is so low that it would take decades to recoup my investment. My heat and hot water are electric as well, so really the only ways for me to reduce my emissions are in the areas of transportation, waste, and the food I choose to eat.
If you want to find out how clean your electricity is, use EPA's Power Profiler:
You plug in your Zip code and it gives you the result. Every region in the United States has a different power mix. What gets tricky is coming up with an average of the baseload mix versus the plants that are brought online only to provide power at times of peak demand. Some of those plants are really dirty (e.g., diesel), while others are relatively clean (natural gas).
Thanks for the link. It looks as though we're living smack dab in the middle of coal country, as that's the source of nearly 80% of our power, with nuclear filling in the remainder.
The thought of solar hot water hadn't crossed my mind at all; from what little I've read it sounds doable. Not sure how well such a system would hold up during the winter months, but it's something to keep in mind.