Current innovations in heat pumps mean they are becoming more efficient, available and economical. The premise: They work like an air conditioner in the cooling cycle and merely reverse the mechanism in the heating cycle, cooling the outside and venting heat to the inside. Air-source heat pumps transfer heat through air and because they move heat around rather than creating heat, they can be a very efficient method of space conditioning—especially in moderate climates.
A typical new heat pump in the United States is on average roughly twice as efficient as electric resistance heat, although performance varies with climate, with optimal performance in moderate climes. While heat pumps can be efficient, they are also more expensive than many types of heating systems, and they generally don’t work well at very cold temperatures. But in the right context and when using a clean energy source, heat pumps should be considered an important strategy for displacing emissions from in-home combustion of fossil fuels.
A recent ACEEE report assessed two potential scenarios for heat pumps’ widespread deployment: replacing electric resistance heat pumps or replacing gas furnaces. The former could reduce residential sector electricity by 2 percent, the latter by even more. Here’s a closer look at some of the ramifications.
Converting homes with electric resistance heat
The report examined replacing both “electric furnaces (which distribute heat via ducts) and electric baseboard heat (heating coils along the baseboard in each room) with heat pumps.” Electric furnaces are popular in the south and nearly 90% of homes with electric furnaces already have central air conditioning. The best time to install a new heat pump, in terms of cost, is when the existing central air conditioner needs replacement. In this scenario, the median simple payback period (time for the energy savings to fully pay back the additional cost) is 4.7 years. For the 17% of homes with electric baseboard heat that also have central air conditioning, the savings were similar. However, for homes without preexisting air conditioners, it’s a bigger investment and the median simple payback is nearly 15 years.
Replacing gas furnaces with heat pumps
A variety of furnace, heat pump, and power plant efficiency levels were analyzed for each of the 20 states included in the report. The research found that electric heat pumps generally use less energy in warm states and offer moderate savings in these states if a heat pump can replace both the furnace and a central air conditioner. But from an economic point of view, given the cheaper cost of natural gas, life cycle costs for gas furnaces in existing homes will be lower than for heat pumps in these states. New construction, which was not part of the report, may tip the equation more favorably as it could eliminate the need (and cost) to install gas service. For cold states (colder than Massachusetts and Pennsylvania), high-efficiency furnaces still use less energy than today’s heat pumps. The technology is not where it needs to be—yet. But the goal is further development of cold-temperature electric heat pumps and gas-fired heat pumps, with an eye to their impressive energy saving potential.
As for next steps, state officials and utilities administrators should do more research to determine which sectors and zones would benefit from heat pumps and which would not. Manufacturers and R&D firms should keep working on making heat pumps perform better in colder climates. Energy efficiency program administrators should launch more programs—particularly pilot programs—to encourage use of heat pumps in warmer states.