Choosing Heat & Airin Washington
All decisions

Start from your house

Heat, west side

Heat, east side

Oil, propane and wood

Cooling

Wildfire smoke

Damp, crawlspaces and ducts

Money and rules

Decisions Your house West side

What do west side winters and summers ask of your house?

Updated . Sources checked November 3, 2026.

West side heating and cooling starts from NOAA's numbers: Sea-Tac's January low averages 37.7F, with no days at or below zero, and its July high averages 77.4F. So heat is the larger job here. Summer is short but no longer safe to ignore, because Sea-Tac reached 108F on June 28, 2021.

A ferry crossing grey Puget Sound with a curtain of rain falling in the distance.
A ferry crossing grey Puget Sound with a curtain of rain falling in the distance.

What to decide, in this order

  • Ductless heat pump or keep the baseboard heaters?

    The core west side question, since electric heat is so common and rebates favor it.

    Ductless heat pump, baseboards stay
    West side electric homes with an open main living area
    Baseboards alone
    Small or lightly heated homes, or homes that lean on wood
    A white electric baseboard heater with a dial thermostat on a wood-paneled wall.

  • New gas furnace or heat pump on the West side?

    A gas house with a mild climate, and a gas price that jumped in 2025.

    New gas furnace
    Furnace has failed, cooling isn't wanted, and budget is tight
    Heat pump
    Cooling matters, or an income-qualified PSE gas rebate is on the table
    A modern condensing gas furnace in a closet, with white PVC vent pipes and metal ducts.

  • Replace the electric furnace, or put a heat pump on the ducts?

    Existing ducts plus resistance heat make a large target for savings.

    Ducted heat pump
    Sound ducts and a furnace near the end of its life
    Ductless, furnace stays
    Furnace still works and the main room is the priority
    New electric furnace
    Only when a heat pump truly can't fit the house
    A low blue house on a wet driveway, with fog hiding the trees behind it, in Bothell in March 2025.

  • Your furnace is fine but you have no AC: AC or heat pump?

    If the furnace is fine and the house has no cooling, this is the first thing to settle.

    Central AC
    You want only summer cooling, and a bid shows a clear gap
    Heat pump, furnace stays
    You want cooling plus a second heat source for mild days
    A large grey and white Craftsman bungalow with a planted front bank on a sunny September day in Wallingford, Seattle.

  • Window AC or a ductless heat pump for your house?

    A low-commitment answer to a few hot weeks, and what it leaves undone.

    Window AC
    One or two rooms, a small budget, cooling only
    Ductless heat pump
    Electric heat you also want to cut, a long stay
    A window air conditioner hung on a bracket in the sash of a clapboard house, seen from outside. Photographed in New Orleans, not Washington.

  • Windows open or closed when it's smoky and hot?

    Smoke and heat can arrive together, and the usual evening habit may not work.

    Keep them closed
    Smoke outside, safe temperature inside
    Open when the air improves
    A clean break in the smoke, even a short one
    Go somewhere cooler
    Too hot to stay safe, or too much smoke indoors
    Seattle's skyline and Space Needle washed out by smoke from the Sourdough Fire and other regional wildfires, seen from Kerry Park in August 2023.

  • Dehumidifier or more ventilation for a damp Washington house?

    West side damp shows up on windows and in basements.

    Dehumidifier
    A closed basement or room that stays above 60 percent
    More ventilation
    Steamy bathrooms and moisture made by daily living upstairs
    A tall beige dehumidifier with a lit display, running in a bare basement.

  • Should a Washington crawlspace stay vented or be sealed?

    Washington's code default and why the marine climate matters.

    Stay vented, finish the ground cover
    Most existing houses with clear vents and no standing water
    Seal it (unvented)
    A designed project that meets the radon and exhaust rules
    Looking through a crawl-space hatch at drain pipes and plastic sheeting that only partly covers a dirt floor.

West side normals, with Spokane for contrast

NOAA 1991-2020 normalSea-TacBellinghamSpokane
January low37.7F34.0F24.7F
January high48.0F46.3F34.5F
July high77.4F72.7F84.4F
Heating degree days a year4,375.85,110.26,462.6
Cooling degree days a year265.075.2514.6
Days of 90F or more a year3.80.420.8
Days with a low of 0F or below0.00.02.2

Sources: NOAA normals for Sea-Tac, Bellingham and Spokane. Normals are 30-year averages at airports. They do not show a heat wave, a hillside or a house near the water.

Why does electric heat dominate the west side decision?

Because it is common and the savings are measured. EIA counts electricity as the main heating fuel in 55% of Washington homes statewide. In the NEEA field metering of 2008 and 2009, ductless heat pumps in Puget Sound homes averaged a seasonal COP of 3.05, or about three units of heat per unit of electricity.

On our running-cost table, that works out to $11.43 per million Btu delivered against $34.87 for baseboard, at 2024 statewide prices. That is our arithmetic, and it ignores your own utility's rate.

Metered homes also kept using their old heat, so a ductless unit serves the main living area and does not replace every baseboard. Most west side utility rebates are written for this situation. Check yours on the utility comparison.

Beads of water on a window pane, with a neighboring house blurred beyond the glass.
Beads of water on a window pane, with a neighboring house blurred beyond the glass.

Is cooling worth planning for on the west side?

Yes, because the risk is rare and severe. Sea-Tac hit 102F, 104F and 108F on June 26, 27 and 28, 2021. The state counted 157 heat-related deaths statewide reported from June 26 to August 31 that year.

Daily demand stays small, though. Metered cooling use in Puget Sound homes with ductless units was 72 kWh a year in that pilot, so a west side cooling choice is about safety on a few days more than about summer bills. A heat pump covers both jobs. For a house that stays with its current heat, see whether a fan is enough and the one cool room option.

North 82nd Street in Seattle during the 2008 snow, with cars buried along both curbs.
North 82nd Street in Seattle during the 2008 snow, with cars buried along both curbs.

What does the damp change?

It adds moisture to the list. EPA says to keep indoor humidity below 60 percent, ideally 30 to 50. A $10 to $50 meter tells you where you stand. Under the floor, a Building America article by WSU authors says that in the marine climates of the Northwest, "vented crawl spaces work acceptably most of the time". The crawlspace hub covers the rest.

What people ask next

Does Bellingham need a different system from Seattle?

It asks for more heat and far less cooling: about 5,110 heating degree days against 4,376, and 0.4 days of 90F or more a year against 3.8, per NOAA normals. Sizing should come from a Manual J load calculation for the house, not the city.

Decide next

Where this came from