My '05 didn't have heated seats as an option... however, we did learn that some features of the car can really impact the fuel economy. One pretty big offender was the rear window defroster, which reduces fuel economy by .9 mpg all by itself (apparently it takes a lot of power to change the temperature of the mass of the glass while continuously exposed to icy cold outdoor weather in order to melt ice, frost, or evaporate condensation).

My "guess" is that the seat heaters may be drawing a similar amount of power. I'm thinking that if you leave them on even when no passenger is sitting in that seat then it might make a noticeable difference in fuel economy.

Does anyone happen to know the amperage of the seat heaters as compared to the amperage of the rear window defroster??