Short definition
A heat pump is a heating and cooling system that moves heat from a low-temperature source — outside air, the ground, or a body of water — into the building, using a refrigerant cycle to do work. It can deliver three to four units of heat per unit of electricity, far better than any combustion or resistance heater. Reversible models also do summer cooling.
What it is
A heat pump is the same refrigerant-cycle technology as a refrigerator, run in reverse and scaled up. The four core components:
- Compressor. Drives the cycle; the only major moving part.
- Condenser. Where hot, high-pressure refrigerant gives up heat to the indoor air or hydronic loop.
- Expansion valve. Drops pressure and temperature.
- Evaporator. Where cold refrigerant absorbs heat from outside air, ground loop, or water source.
Refrigerant cycles between liquid and vapor phases at each stage, carrying heat from outside to inside. Because the system moves heat rather than generating it, the energy ratio is much better than 1:1 — typical residential heat pumps deliver 2.5 to 4.5 units of heat output per unit of electricity input, depending on outdoor temperature and design.
Heat pump types:
- Air-source heat pump (ASHP). Draws heat from outside air. Cheapest install. Performance declines as outdoor temp drops, but cold-climate variants stay efficient down to roughly 0°F.
- Ground-source heat pump (GSHP / geothermal). Buried pipe loop draws heat from soil. Higher install cost (drilling), highest efficiency, near-constant performance year-round.
- Air-to-air vs. air-to-water. Air-to-air pushes heated indoor air directly through ducts or ductless cassettes (mini-splits). Air-to-water heats a hydronic loop for radiators or radiant floor — useful when retrofitting a hydronic-heated home.
A reversing valve makes the cycle bidirectional, so the same equipment that heats in winter can cool in summer.
Why it matters to a homeowner
Heat pumps are the most consequential residential energy-system shift happening in WA right now, for three reasons.
First, efficiency. A heat pump’s coefficient of performance (CoP) of 3 to 4 means it runs at 300–400% efficiency compared with a 95% condensing gas furnace. On WA’s mild winters, the operating-cost gap can favor heat pumps even at higher electric rates.
Second, rebates and incentives. PSE, Seattle City Light, Tacoma Power, and Snohomish PUD all offer heat-pump rebates. The federal Inflation Reduction Act 25C tax credit covers 30% up to $2,000 of install cost. The Home Energy Rebates (HEAR) program adds up to $8,000 for income-qualified households. Stacked incentives can cover a substantial fraction of a $12,000–$28,000 ASHP install in WA.
Third, cooling. Most older WA homes don’t have central AC. A heat pump replacement of an old gas furnace adds cooling to the building for free — the same equipment.
The catch: heat pumps are sensitive to install quality. An undersized unit runs auxiliary resistance heat constantly during cold snaps, killing the efficiency advantage. An oversized unit short-cycles and dehumidifies poorly. A botched refrigerant charge degrades CoP year-round. Ask whether the contractor does a Manual J load calculation and verify their EPA Section 608 refrigerant certification.
When you’ll encounter this term
- An old gas furnace or boiler is at end of life and you’re getting replacement quotes.
- A PSE, SCL, Tacoma Power, or SnoPUD rebate flyer.
- A Manual J load calculation as part of a quote.
- A real estate listing for a newer WA home advertising “heat pump heating and cooling.”
Common variants and disambiguation
- Heat pump (space heating) vs. heat-pump water heater (HPWH). Same physics, different application. A heat pump heats your house; an HPWH heats your domestic hot water tank. Both use a compressor and refrigerant.
- ASHP vs. GSHP. Air-source draws from outside air (cheaper install, performance drops in cold). Ground-source draws from soil (much more expensive due to drilling, but near-constant performance year-round).
- Air-to-air vs. air-to-water. Air-to-air heats indoor air directly. Air-to-water heats a hydronic loop. Air-to-water is the path for hydronic-heated WA homes considering electrification.
- Single-stage vs. cold-climate. Single-stage is on/off at a fixed capacity. Cold-climate variable-speed (inverter-driven) heat pumps maintain high CoP at low ambient temperatures — important inland and east of the Cascades.
Common failure modes
- Defrost cycle stuck on. Outdoor coil ices over and the unit defrosts repeatedly. Indicates refrigerant or sensor problem; needs an EPA-certified technician.
- Compressor short-cycling. Often a refrigerant charge issue (over- or under-charged).
- Refrigerant leak. Requires EPA Section 608 certified handling for repair and recharge.
- Auxiliary heat running constantly. Heat pump undersized or in fault — auxiliary electric resistance backup is much less efficient and burns through electric bills.
- Outdoor unit obstruction. Leaves, snow, or vegetation around the outdoor unit. Clear annually.
Washington note
WA is one of the friendliest US climates for heat pumps. Mild Puget Sound winters rarely drop below 25–30°F for sustained periods, keeping ASHP CoP in the 3+ range most of the heating season. East of the Cascades, Spokane and inland valleys see lower winter lows where cold-climate variants are appropriate.
WSEC residential R403 increasingly favors heat pumps on new construction, and the state’s Clean Buildings Act drives commercial decarbonization. Permit and inspection are required: a mechanical permit for the heat pump itself and an electrical permit for the new circuit and disconnect. Refrigerant work is regulated under EPA Section 608; only certified technicians can charge or recover refrigerant.
Refrigerant phase-down under the federal AIM Act is moving residential heat pumps from R-410A to lower-GWP options (R-32, R-454B, R-290) through 2024–2026. New equipment installed in WA today may use a different refrigerant from the unit it replaces; service techs need to be trained on the specific refrigerant.
The rebate stack in WA can be substantial. PSE, Seattle City Light, Tacoma Power, and Snohomish PUD each have their own program, and they layer with the federal IRA 25C credit and HEAR (income-qualified) rebates. A typical WA ASHP install can see $2,000–$12,000+ in combined incentives depending on income, utility, and product specifics.
FAQ
Are heat pumps efficient in Washington’s cold weather?
Yes for most of WA. Puget Sound winters are mild enough that standard ASHPs maintain CoP above 2.5 nearly all season. East of the Cascades, where winter lows can hit single digits, cold-climate variable-speed heat pumps are the right pick — they keep CoP above 2 down to 0°F or below. Pair with electric resistance backup for the rare deep cold.
How much does a heat pump cost installed in Washington?
Air-source whole-home installs run $12,000–$28,000 in WA depending on house size, ductwork condition, and equipment tier. Ductless mini-split single-zone systems start around $4,000–$8,000. Ground-source heat pumps run $25,000–$60,000 because of drilling. Stacked rebates and the federal IRA 25C credit can reduce out-of-pocket cost substantially.
Do I need a new electric panel for a heat pump?
Sometimes. A whole-home ASHP typically draws 30–50 amps; a 100-amp service running a gas-heated home may need an upgrade to handle the new circuit alongside existing loads. A load calculation by a licensed electrician answers definitively. Panel upgrades run $2,500–$5,000 in WA on top of the heat-pump install.