Marginal cost - Wikipedia, the free encyclopedia
Unless you're contemplating getting rid of the gas dryer, stove, and hot water heater, the hookup fee is a sunk cost. You pay $149/yr for gas hookup, regardless of whether you install a furnace or a heat pump. Your first therm of the year costs $150, and each subsequent therm costs $1.
I accounted for taxes and fees that rise with my usage, and I excluded taxes and fees that don't.