Electric Heat Pumps
- A heat pump is like a conventional air conditioner except it also can run in reverse.
- Heat pump efficiency often exceeds 200%.
- Heat pumps do not emit indoor products of combustion.
Heat Pump Advantages
An electric heat pump has numerous advantages compared to a natural gas-fired furnace, an oilfired furnace, or an electric resistance baseboard heating system.
- Higher efficiency ratings
- Lower operating costs
- Lower initial capital cost (all electric)
- Electricity is available everywhere
- Heats and cools
- No indoor products of combustion (including carbon monoxide)
- No venting required
- No open flame
- Extended equipment life
- How a Heat Pump Works
A heat pump is like a conventional air conditioner except it also can run in reverse and provide indoor heat in the winter. Both the air-source heat pump and the air conditioner contain two sets of coils, a compressor, and fans to circulate the conditioned air. However, a heat pump also contains a valve that enables it to switch between "air conditioner" and "furnace." When the valve is switched one way, the heat pump acts like an air conditioner, and when it is switched the other way it reverses the flow of the refrigerant and acts like a heater. It does this by extracting available heat from the outside air and transferring or ''pumping'' it inside a home. During the summer, the heat pump reverses this operation, extracting heat from the air inside a home and pumping it outside.
Geothermal heat pumps (ground-source) are more versatile than air source heat pumps because they have a lower setpoint temperature and can also provide hot water. The backup or supplemental heating needs are not as great. Geothermal heat pumps exchange heat with the earth through a system of buried plastic pipes called a ground heat exchanger. In the winter, fluid in the pipes extracts heat from the earth and carries it through the system and into the building. In the summer, heat is pulled from the building, carried through the system, and conducted into the cool earth.
How NOT to Use Your Heat Pump Thermostat
The way you run your heat pump may be costing you a lot of extra money. With heat pumps, there's an extra setting on the thermostat. In addition to heat, cool and off, there's a setting for emergency heat. A heat pump pulls heat from the outside air (unless you have a ground source heat pump, which pulls heat from the ground or a body of water). As it gets colder outside, your heat pump is able to pull less heat inside. Eventually it can't meet the heating load of the house. That's where supplemental heat, which is NOT the same as emergency heat, kicks in.
What happens when your heat pump can't keep up?
For most heat pumps, the supplemental heat source is electric resistance (strip) heat. When the heat pump can no longer pull enough heat from outside to meet the heating load of the house, the electric resistance heat comes on and supplements the heat pump. If you have an all-electric home, your supplemental heat source is almost certainly electric resistance heat.
If your home has natural gas, propane or fuel oil, the supplemental heat may be supplied by a furnace. This is called a dual-fuel system. Most of these are connected in a way that when it gets too cold outside for the heat pump to supply all of the heat, the heat pump shuts off and the furnace supplies all of the heat.
If your supplemental heat is supplied by electric resistance, it's 100% efficient. That may sound good, but it's not. The heat pump, by that same measure, is 200 to 300 percent efficient, so when the heat pump by itself can't supply all the heat your home needs, you at least want it to supply as much as it can. That gets you more of the 200-300% efficient heat and less of the 100% efficient heat.
Unfortunately, some people have a misunderstanding about how this works, and sometimes that misunderstanding comes from a surprising source.
What's your emergency?
For some reason, a lot of people overlook that the thermostat says 'emergency,' and not 'supplemental,' and think that when it gets cold outside they have to switch over to emergency heat. Now here's the kicker. Evidently they have good reason to think that, because many times their HVAC company told them to switch over when it's 'in the thirties' or when it's 'below freezing.'
How are people supposed to learn the correct way to use their thermostat for a heat pump when they're getting such bad advice from the person who's supposed to know? If you switch to emergency heat, you're going to pay a lot more, perhaps hundreds of dollars more, to heat your house.
In short, if you have a heat pump with electric resistance heat as the supplemental heat source, keep the thermostat in the 'heat' setting. Do NOT use the 'emergency heat' setting unless it's really an emergency; for example, when the heat pump doesn't work. You won't notice a difference in how well it heats your home, but you will notice a difference in your electricity bills.
Considering the installation of a heat pump? Contact us or call 1-800-879-4056 for more information.
White River Valley Power Factor has been prepared solely for the purpose of providing helpful information to users of this service. The information has been compiled by Tech Resources, a contractor to White River Valley Electric; however, no representation is made by either Tech Resources or White River Valley Electric as to the completeness or accuracy of the information contained therein. In particular, some information may be incomplete, may contain errors or may be out of date. In addition, neither Tech Resources nor White River Valley Electric endorses any product or service mentioned therein. Energy Vanguard Blog also was a contributing source for some of this information.