Heat pump or gas furnace in western Washington?

If you live in western Washington and your gas furnace needs replacing, you have three main choices. You can install a heat pump, a hybrid system that pairs a heat pump with a gas furnace, or another gas furnace. Cold-weather performance is easier to judge than running cost. In a normal year, Sea-Tac stays well above the 5°F test point used in cold-climate heat pump standards. Running cost depends on your own electric and gas rates. This guide gives you the climate numbers, the equipment standards, Washington's current energy prices and PSE's hybrid option. It does not turn them into a cost estimate.

How cold does it get in western Washington?

NOAA's 1991–2020 normals for Seattle-Tacoma International Airport show 4,375.8 heating degree days and 265.0 cooling degree days a year. Heating is by far the larger need.

December is the month with the most heating demand in the normals we reviewed. It has 711.4 heating degree days and a normal average high of 47.0°F.

Nights at or below 10°F are rare at Sea-Tac. The airport averages 25.2 nights a year at or below 32°F and 0.0 nights at or below 10°F. These numbers are 30-year averages for one station. A single winter, or a home at a higher or more exposed spot, can see colder nights than these normals show.

What makes a heat pump a cold-climate heat pump?

NEEP and ENERGY STAR both publish cold-climate standards for air-source heat pumps. Northeast Energy Efficiency Partnerships (NEEP) says its cold-climate specification is designed to identify heat pumps that heat efficiently in cold climates, defined as International Energy Conservation Code (IECC) climate zone 4 and higher.

Version 4.0 of the NEEP specification sets two key rules. The compressor must be variable capacity, which means it has three or more operating speeds or adjusts continuously. The heat pump must also reach a COP of at least 1.75 at 5°F when running at maximum capacity. COP, or coefficient of performance, compares heat delivered with electricity used. A COP of 1.75 means 1.75 units of heat for each unit of electricity.

ENERGY STAR's Version 6.2 heat pump requirements add a capacity test. A cold-climate unit must keep at least 70% of its 47°F heating capacity when the outdoor temperature is 5°F. PSE uses both thresholds for its heat pump upgrade rebate: a COP of at least 1.75 at 5°F, and at least 70% of rated 47°F capacity at 5°F.

In an average year, Sea-Tac sees no nights at or below 10°F. The 5°F test point therefore sits below what the airport sees in a normal winter.

Washington electricity and natural gas prices

The U.S. Energy Information Administration (EIA) reports state average prices. Washington's average residential electricity price was 14.71 cents per kilowatt-hour in July 2026, up from 13.45 cents in July 2025. A single summer month does not reflect heating season, so the year-to-date figures are more useful. They show 14.40 cents from January through July 2026, compared with 12.74 cents for the same months of 2025.

For natural gas, Washington's average residential price was $17.62 per thousand cubic feet in 2025, up from $12.72 in 2024. The U.S. average was $15.34 in 2025.

These two prices use different units: kilowatt-hours for electricity and thousand cubic feet for gas. We have not converted them into a cost per unit of heat or an annual bill estimate. Statewide averages may also differ from your utility's rates.

Utilities make efficiency claims, and they are not bill estimates. PSE says on its moderate-income heat pump page that heat pumps "can reduce your electricity use by up to 50% compared to furnaces and baseboard heaters" and are "typically 2-3 times more efficient than gas furnaces." Tacoma Power says that, compared with electric resistance heat such as an electric furnace or baseboard heaters, a heat pump can reduce electricity use for heating by 50%. Using less energy does not by itself mean a lower bill when the fuel prices differ.

PSE's hybrid heat pump option

A hybrid system pairs a heat pump with a gas furnace. On its hybrid heat pump page, PSE says that "as the weather gets colder and drops below 35 degrees, the gas furnace kicks in, quickly providing warmth."

PSE says bill impacts "may vary significantly depending on the difference between natural gas and electric rates." It adds that gas use may go down while electric use goes up, which offsets some of the savings you may have expected.

PSE's rebate flyer (rev. 03/26) lists $1,500 for a natural gas furnace to hybrid heat pump conversion, or $2,400 at the Efficiency Boost level for income-qualified customers; our guide to heat pump rebates from PSE, Seattle City Light, Tacoma Power and Snohomish PUD covers the other programs.

Whichever system you choose, the same flyer has thermostat advice. Set it to 68°F or lower when you are home and awake. With a heat pump, lower it only 2 to 3°F when you are asleep or away, compared with 7 to 10° for a traditional furnace.

Does Seattle's building emissions rule apply to houses?

Seattle's Building Emissions Performance Standard (BEPS) "requires nonresidential and multifamily buildings larger than 20,000 square feet" to meet stronger emissions targets over time. A single-family house is neither, so BEPS does not cover it. This guide did not review other city or state energy codes.

If your home heats with oil, the City of Seattle says on its Clean Heat program page that heating oil "is the least efficient, most expensive, and most polluting form of home heating in Seattle."

For a gas-heated home, the choice comes down to three things: the cold-weather ratings of the heat pump you are quoted, your own electric and gas rates, and which rebates you qualify for.