I agree in principle, but I don't think this is the same thing, quite. This isn't like Kyoto emission credits, which are finite and can be purchased only from those nations who don't use them. (The idea being to keep greenhouse emissions on a reducing schedule.) This is paying a solar-electricity company for the electricity you use. It's unlikely that the electrons flowing into the Gore's house are all solar, but he paid through the Green Power Switch program for his 221,000 kilowatt-hours, so $30,000 worth of solar/geothermal/green energy went into the Tennessee grid.