Energy cost comparison for different fuels and systems

My previous post shows the results we obtained when we ran annual energy simulations for the same house in Asheville, NC. Obviously the actual energy use depends on the house design, but this shows how systems perform relative to one another in the same house.

You can see that solar and heat pump water heaters are by far the most inexpensive to run. This is followed by on-demand natural gas, which is about $65 per year ahead of a regular storage tank electric water heater. Alone, that's not enough to justify the service charges to have gas in the house. At $2 per gallon, the propane tankless is barely better than the electric tank, and at $3.30, it's much worse. Usually I only recommend propane tankless for second homes where usually no one is using it, but on occasional weekends 14 people in a row need to use the shower.

In terms of energy cost, geothermal wins for space conditioning. Using a heat pump with furnace backup is less expensive than using a heat pump alone - here it was 22% better, or $100 savings. Again, it's not a compelling economic case to pay gas service charges and install another piece of equipment. With propane at $2 per gallon, the savings are smaller, and with propane at $3.30 per gallon, you'd be better off with the heat pump alone. The gas furnace is easier to justify if you want a fast recovery time, or if the home occupant is really sensitive to moving air and likely to complain about a heat pump. But most of us would do just fine. The systems that use just a furnace or boiler alone always cost more to operate. If these are augmented with solar, this could turn around, but most homes would need a lot of solar. One or 2 panels isn't likely to do it.