Heating accounts for 29% of all energy used in the average American home, according to the U.S. Department of Energy, so it makes perfect sense to choose the most energy-efficient heating system possible. Ductless minisplit heat pumps, wood and pellet appliances, electric thermal storage devices, ground- and air-source heat pumps, and gas-burning furnaces and boilers are potential choices. But there is no single solution that covers all situations. Climate, utility costs, labor rates, and the fuel all should figure into a decision on which heating appliance to buy.
Houses with minimal air leaks, lots of insulation, and multipane windows require less energy to remain comfortable in cold weather than older houses or those built to code minimums. In high-performance houses like these, heating equipment can be of lower capacity, and therefore less expensive to install and operate.
Passive solar design is another way of lowering heating bills. Orienting the house with its long axis east to west—so windows on the south face can capture the sun—and choosing windows with low U-values and the correct solar heat gain coefficients for the climate are among the steps that can reduce the need for fuel-fired space heating.
Keeping heating loads at a minimum pays big dividends, not just when buying a heating system initially but also in keeping operating costs down. For example, consider a house that’s been certified under the Passive House standard, a building method that originated in Germany and is now relatively common in Europe. It sets tough benchmarks for airtightness, total energy use, and energy use for heating and cooling, and houses built to these standards far exceed the performance of conventionally built houses in the United States. Passive House Institute US estimates a house meeting its standard would use as little as 10% of the heat energy of a conventionally built home.
Finally, whether the house is old or new, make sure your heating contractor calculates heat loss so the equipment can be sized correctly. Buying oversized equipment, which contractors sometimes recommend just to be safe, is a waste of energy and money.
Getting the full story on the energy efficiency of a particular heating system requires understanding the difference between “site energy” and “source energy.” Site energy is the amount of energy that’s used at the house. As defined by the U.S. Environmental Protection Agency, source energy represents the total amount of raw fuel that’s used, including transmission, delivery, and production losses.