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Get a wood fired water heater.
I build wood fired hot water heaters out of discarded gas hot water heaters. See www.fcpj.org for a video. As you can see from the video its not a unit for suburbia but in the country it works great. One firing gives two days of hot water if you take short showers.
I like the idea of a wood fired hot water heater, but I think the particulate pollution would become a major contributor to smog if this type of hot water heater became popular. I live in a city where some people still use wood as a source of heat in the winter and the smoke from burning wood even in a ultra efficient wood stove causes smog alert days.
You are correct this unit would not pass EPA standards for particulates. If you live in an area like we do where particulates are only a problem when we have a wildfire a wood fired water heater is a viable alternative. Because of the wood fired water heater our electric bill is around $25 a month. We use an average of 5 KWH per day of electricty. We also heat with wood.
