How Does a Heat Pump Work? A Simple NH Homeowner's Guide
A heat pump moves heat from one place to another instead of creating it. In summer it pulls heat out of your home and dumps it outside, working as an air conditioner. In winter it reverses, pulling heat out of the outdoor air (even sub-zero air contains usable heat) and moving it inside. Because moving heat takes less energy than producing it, a heat pump can deliver 2 to 3 units of heat for every 1 unit of electricity consumed.
At A.J. LeBlanc Heating, we install and service heat pumps across southern NH. Here is what is happening inside the equipment.
The basic principle: refrigerant and pressure
A heat pump runs a closed loop of refrigerant (typically R-410A on older systems, R-32 or R-454B on newer ones) that changes between liquid and gas as it absorbs and releases heat. Four components do the work:
- Compressor: compresses the refrigerant gas, raising its temperature.
- Condenser coil: the hot, pressurized refrigerant releases its heat to the surrounding air or water and condenses back to a liquid.
- Expansion valve: the liquid passes through a restriction that drops its pressure and temperature sharply.
- Evaporator coil: the cold, low-pressure refrigerant absorbs heat from the surrounding air or water and evaporates back to a gas.
The compressor pulls the gas back in and the cycle repeats. A reversing valve is what turns a standard AC into a heat pump: by switching the direction the refrigerant flows, the indoor and outdoor coils swap which one absorbs heat and which one releases it. Same hardware, opposite directions, so the unit both cools and heats.
Yes, even cold outdoor air contains usable heat
To a refrigerant running at very low pressure (and therefore very low temperature, around minus 30°F), outdoor air at minus 5°F is still warmer and gives up heat to the refrigerant. The compressor then raises that heat to a useful indoor delivery temperature. Cold-climate heat pumps (CCHP) are built for this, using variable-speed inverter compressors, enhanced vapor injection, and improved refrigerants to extend capacity well below zero. Mitsubishi (Hyper-Heat), Bosch (IDS), Fujitsu (XLTH), Daikin, and LG all make CCHP units rated for NH winters.
Why heat pumps are so efficient
Electric resistance heat produces at best 1 unit of heat per 1 unit of electricity, a coefficient of performance (COP) of 1.0. A modern cold-climate heat pump does much better:
- COP of 3.0 or higher at 47°F outdoor
- COP of roughly 2.0 to 2.5 at 17°F outdoor
- COP of roughly 1.5 to 2.0 at 0°F outdoor
- Continued heat delivery (at lower COP) down to minus 13°F and below
That is less than half the electricity of resistance heat for the same output during most of the season. Against fossil fuels, the cost per BTU often comes out lower too, especially in NH where electricity rates are competitive with oil and propane.
Where heat pumps fit in NH
Three configurations cover most NH homes:
- Central heat pumps: an outdoor condenser paired with an indoor air handler, distributing air through existing ductwork. Best for homes that already have central AC and want off a fossil-fuel furnace.
- Ductless mini splits: an outdoor unit paired with one or more indoor heads on walls, ceilings, or floors. No ductwork required, which makes them the most popular option for older NH homes with hydronic heat.
- Dual-fuel (hybrid) systems: a heat pump paired with a backup gas, propane, or oil furnace. The heat pump handles most of the season at high efficiency; the backup takes over on the coldest days. Typically the lowest year-round operating cost in NH.
Maintenance basics
Heat pumps need annual professional service to hold efficiency and warranty coverage. A visit includes cleaning the indoor and outdoor coils, checking refrigerant charge on central and ducted systems, verifying electrical connections, capacitor health, and reversing valve operation, inspecting defrost controls, and replacing filters. On your own, keep the outdoor unit clear of leaves and snow, maintain 18 to 24 inches of clearance around it, and change indoor filters on schedule.
Schedule a heat pump consultation
If you are considering a heat pump for your NH home, whether a full replacement, a dual-fuel pairing, or supplemental heat and cooling in specific rooms, contact A.J. LeBlanc Heating or call 603-623-0412. Serving New Hampshire families since 1928.
Frequently Asked Questions
How efficient is a heat pump compared to electric resistance heat?
A modern heat pump can deliver 2 to 3 units of heat for every 1 unit of electricity consumed; electric resistance delivers exactly 1 unit per 1 unit. The heat pump uses less than half the electricity for the same output during most of the heating season.
Do heat pumps work below zero in New Hampshire?
Yes. Cold-climate heat pumps are rated to deliver useful heating down to minus 13°F and lower. Capacity drops as temperatures fall, which is why most NH installations include a backup heat source.
Does a heat pump cool too?
Yes. The same equipment cools in summer and heats in winter. A heat pump is essentially an air conditioner with a reversing valve.
How long does a heat pump last?
Modern heat pumps typically last 12 to 15 years with proper maintenance. The outdoor unit takes more weather abuse than a comparable AC condenser, so annual service matters more.
What is the difference between a central heat pump and a mini split?
A central heat pump uses ductwork to distribute air through the home. A ductless mini split delivers air directly from one or more wall, ceiling, or floor-mounted indoor units. Mini splits are zoned by design; central systems serve the whole home.