Fossil fuels, because I have a wood stove to heat the house anyway. Showers would be cold, but I could heat water over the stove and sponge bath or something. Bike to class ~4 miles away. The biggest thing I would worry about is the pipes freezing, I'd probably have to use an extension cord and a blowdryer to keep them warm. Losing electricity and running water would be a much greater hassle though.