Peter Thomson, on Gristmill, writes about switching out an oil-eating monster in his basement with a combined heat and power system which only cost 15% more than a conventional high efficiency gas boiler:
Combined heat and power--or cogeneration, as it’s also known--captures the waste heat from generating electricity to heat a building. Thomas Edison himself thought it up in the late 1800s, but only now, in the face of 21st century energy challenges, is it starting to catch on for small-scale use. Ours is one of the first 80 or so residential MCHP units to be installed in the entire country. And it should cut both our total annual energy cost and our carbon footprint by roughly half.