A good price may not really be a good deal. With whom you spend your money (and how they treat their neighborhood) can say a lot about your sustainability.

For instance, from what company do you buy your paper, electricity or gasoline, and how sustainable are they? Do they pollute? Use renewable energy? What is the recycling policy?

If you look up "commodity" in Webster's you should see a picture of a gallon of gasoline. Like toothpaste, the price differences are minor, and the quality is nearly impossible for consumers to tell apart.

The Sierra Club has rated the major oil companies for their environmental policies in an online guide. If you guessed ExxonMobil (hello Valdez!) as the "bottom of the barrel" you are correct. The Sierra Club rates BP and Sunoco most highly, so they are worthy of your business. Since gas stations are generally clustered, switching to the most sustainable company could not be easier, and any difference in cost probably washes out over the year as prices vary so much.

Yes, it is somewhat of an encumbrance on consumers to ask them to learn the environmental policy of every company, but if you start with the obvious choices like gasoline, appliances, or cars, the subject of sustainability will start coming up more often.