Heat Pump vs Gas Furnace in Seattle: Which Is the Better Choice?

Heat pump vs gas furnace in Seattle comes down mostly to your electric utility. On City Light’s current rates, a heat pump costs less to run than a 95% efficient gas furnace whenever its coefficient of performance (COP) is above about 2.2, which modern units clear most of the winter. On PSE electricity the break-even is about 3.4.

About a third of Seattle households heat with gas, according to Census data, so this is the most common decision behind a heat pump project. The Seattle Heat Pump Company plans and manages furnace to heat pump conversions and dual fuel systems in Seattle and King County, with the work carried out by licensed and insured contractors. This guide lays out the numbers so you can make the call for your own house.

Side by side

Running cost depends on who sells your electricity

The comparison is a ratio. A gas furnace at 95% efficiency turns almost all of the gas’s energy into heat in your house. A heat pump delivers more heat than the electricity it uses; a COP of 3 means three units of heat for each unit of electricity. Whether the heat pump wins depends on how expensive a unit of electricity is compared with a unit of gas.

Here is the math using current energy charges, leaving out fixed monthly charges and taxes. PSE sells gas at about $1.67 per therm, which works out to about $17.57 per million BTU of heat delivered by a 95% furnace.

A heat pump’s COP is not a fixed number. It is highest in mild weather and falls as the outdoor temperature drops. That is good news in Seattle, where most heating hours fall between the 30s and the 50s and only about one night a year reaches 20°F or colder at Sea-Tac. Heat pumps are rated at 47°F and at 17°F, and a modern variable-speed unit typically runs well above a COP of 2.2 through most of that range. On City Light power, that makes a heat pump the cheaper heat source through most of the winter.

On PSE electricity, the bar is higher. A heat pump still beats gas in mild weather, but near freezing and below, the furnace can be cheaper per unit of heat. That gap is the economic reason dual fuel is common on the Eastside.

Three more factors move a real bill:

• Fixed charges. If switching to a heat pump lets you drop gas entirely, including the water heater, range and dryer, you also stop paying PSE’s gas basic charge, about $14 a month. Keeping any gas appliance keeps that charge.
• Controls and sizing. An undersized heat pump or a thermostat left on furnace settings leans on electric backup heat, which has a COP of 1 and erases the savings. See the backup heat settings guide.
• Rate changes. City Light raised rates an average of 5.4% on January 1, 2026. PSE has requested further increases of about 17.75% for electricity and 12.93% for gas; those are requests, not approved rates.

None of this is a savings guarantee. The operating cost guide works through annual estimates with your heating load.

Comfort: what each one feels like

A gas furnace heats air to well above body temperature and pushes it out in short, strong bursts. Rooms warm fast, then cool off until the next cycle. A heat pump delivers air that feels warm rather than hot, and it runs longer and more steadily to deliver the same heat. People used to a furnace sometimes read that cooler supply air as “not working.” It is how the system is designed, and with a variable-speed unit it usually means more even temperatures from room to room.

Two things can make a heat pump feel worse than it should. Ducts sized for a furnace can be too restrictive for the higher airflow a heat pump needs, leaving far rooms cool. And deep nighttime setbacks can trigger backup heat during morning recovery. Both are design and setup problems, not reasons to avoid a heat pump, and both should be checked before equipment is chosen. See using a heat pump with existing ductwork and the variable-speed comparison.

In damp weather near freezing, a heat pump also runs defrost cycles, briefly reversing to clear frost from the outdoor coil. A furnace never does that. The Seattle winter guide explains what normal defrost looks like.

Cooling changes the comparison

For decades, the gas furnace comparison was about heating alone, because many Seattle houses had no air conditioning. That has changed. Sea-Tac’s cooling degree days roughly doubled from 176 a year in the 1990s to 337 a year over 2016 to 2025, and the June 2021 heat dome set an all-time record of 108°F. About 53% of Seattle-area homes had a primary air conditioning source in 2021, up from about 31% in 2013, according to the American Housing Survey.

So the real comparison for many houses is a heat pump against a furnace plus a new air conditioner. A heat pump uses the same kind of outdoor unit as a central AC, with a reversing valve that lets it heat too. If you are adding cooling anyway, the heat pump gives you efficient heating from the same equipment. See central air with a heat pump for the cooling side.

Installation scope

A ducted heat pump on usable ducts typically runs about $6,700 to $20,000 in the Seattle area. That range assumes ducts that pass a static pressure test; duct changes and a panel upgrade, when needed, add to it. The installation cost guide covers the drivers.

A heat pump job carries scope a furnace swap does not: a refrigeration permit that only a licensed refrigeration contractor can obtain, a dedicated circuit and outdoor disconnect (panel requirements), an outdoor location that meets Seattle’s noise limits, and a Manual J load calculation that the energy code requires. Those steps exist because a heat pump’s performance depends on them, and they are where good and poor installations part ways.

The middle path: dual fuel

You do not have to choose one or the other. In a dual fuel system, the heat pump’s indoor coil sits on the gas furnace, and the thermostat hands heating to the furnace below a changeover temperature. The heat pump covers the mild majority of the season and all of the cooling; the furnace covers the coldest hours.

Dual fuel makes the most sense when:

• the furnace is fairly new and its blower can move the heat pump’s airflow
• the house is on PSE electricity, where gas is cheaper on cold days
• you want to avoid a large electric backup heater, which can sometimes avoid a panel upgrade

On City Light power, the economic changeover point sits lower, because the heat pump stays cheaper than gas down to colder temperatures. PSE’s hybrid rebate of $1,500, or $2,400 for income-qualified households, applies only to customers who buy both gas and electricity from PSE, so it does not reach Seattle homes. See dual fuel heat pumps and the PSE rebate guide.

Air-source vs geothermal

Searches for heat pump options often turn up geothermal, or ground-source, heat pumps. They are a different machine with a different set of trade-offs.

An air-source heat pump exchanges heat with outdoor air. A ground-source heat pump exchanges heat with the ground through a loop of buried piping, either in vertical boreholes or in horizontal trenches. Below the surface, the ground holds a far steadier temperature than winter air, so a geothermal system keeps a high COP on the coldest night and needs no outdoor fan unit.

The cost of that steadiness is the loop. Installing it means drilling or trenching, which requires equipment access to the yard, space for the bores or trenches, and restoration afterward. On a narrow city lot with mature landscaping, that can be difficult or impractical. The project involves more trades, more permits and a much higher installed cost. The federal residential clean energy credit that once covered geothermal systems also ended for expenditures after December 31, 2025.

Seattle’s climate narrows the gap. Because winters are mild, an air-source heat pump spends most of its time in conditions where it already runs efficiently, so the ground loop buys less extra efficiency here than it would in a cold inland climate. The Seattle Heat Pump Company plans air-source systems only and does not install geothermal; if a ground-source system interests you, a geothermal specialist can assess your lot.

When each choice makes sense

Keeping the gas furnace, alone or as dual fuel backup, tends to make sense when the furnace is fairly new, the house is on PSE electricity, or the house loses heat fast and envelope work is planned before resizing.

A heat pump as the main heat source tends to make sense when the house is on City Light, when the furnace and the air conditioner are both near the end of their lives, when you want cooling, or when you want to drop gas service. Homes still heating with oil are a separate case, covered in the heat pump vs oil furnace guide.

Next step

The decision rests on numbers you can get: your utility, your furnace’s age and blower size, your ducts’ static pressure, your panel’s capacity and the house’s heat loss. An assessment gathers them, and the cost estimator gives a range before you share contact details. Call or send a few details about the house and the furnace you have now to get started.