Has anyone done the math on whether an electric or natural gas furnace is most cost effective? I live in a 1500SF multiunit condo bldg and deciding whether to replace my current gas furnace with another gas furnace or electric. We don't know what our winter heating bill will be like since we only moved in a couple months ago. The place has been quite warm thus far. Even today when it's been in the 50s we had our windows open and it was in the 70s indoors, so there is some indication that the unit will be relatively warm.