gas forced air furnace... its OOOOLD but it works well and is pretty cheap on the bills. I keep the thermostat set at 66.

:edit: winter here is usually a few cold spells lasting a few days up to a week... maybe a grand total of three weeks of witch's titty cold dispersed over the fall/winter/spring. We also get beautiful 70* days in the middle of winter. It varies pretty wildly.