HVAC Cost in Seattle, WA: System Replacement and Heat Pump Guide (2026)
Replacing an HVAC system in Seattle usually means answering a bigger question first: ducted or ductless, and gas or heat pump. For the full local picture see the Seattle HVAC hub, or skip ahead and get three local quotes. Seattle's older housing stock, its short but increasingly serious cooling season, and real utility incentives for heat pumps all push these decisions in a specific direction, and the right answer for a 1925 Beacon Hill cottage is often not the right answer for a 1980s West Seattle rambler.
By Homeowner Henry · HVAC · Published September 7, 2026 · 9 min read
Ducted, ductless, or hybrid: matching the system to your house
The first question in a Seattle HVAC replacement is not brand or efficiency rating, it is whether your house has usable ductwork. Craftsman and pre-1950 homes in Ballard, Wallingford, Beacon Hill, and Rainier Valley frequently have no ducts at all, having relied on radiators or wall heaters, or ducts so undersized they cannot move enough air for cooling.
For those homes, a ductless mini-split system - one outdoor condenser feeding two to four indoor wall or ceiling cassette units - is usually the most practical path to both heating and cooling. It avoids opening walls and ceilings to run new duct trunks through a tight crawl space or attic.
Homes with adequate existing ductwork, common in postwar West Seattle, Magnolia, and parts of Green Lake, are better candidates for a full ducted system: either a conventional gas furnace plus AC, or increasingly a ducted heat pump that handles both heating and cooling from one system.
Some houses land in between - decent ducts to the main floor but none to a finished basement or an addition - and the right answer there is often a hybrid: central ducted equipment for most of the house plus one ductless head for the room the ducts do not reach.
What full system replacement costs in Seattle
A conventional full replacement - new AC and gas furnace - runs $10,000 to $18,500 in Seattle, reflecting labor rates that run above the national average. A ducted heat pump conversion, replacing an existing furnace with a heat pump and matched air handler, runs $12,500 to $24,000 before incentives.
Ductless mini-split systems for homes with no ducts run $6,000 to $14,500 for one to two zones, scaling up for each additional indoor head - a common configuration in Seattle bungalows is three or four zones to cover the main living area plus bedrooms.
Oil-to-heat-pump or oil-to-gas conversions run $9,500 to $22,000, a wider range because it includes professional decommissioning of the old oil tank in addition to the new equipment - a step that should never be skipped or handled informally.
Every one of these ranges assumes normal access. A finished basement, a tight crawl space, knob-and-tube wiring that complicates an electrical panel upgrade, or an oil tank that turns out to need soil testing can all push a bid toward the top of the range or above it.
Heat pump incentives and the electrical work behind them
Seattle City Light offers rebates on qualifying heat pump installations for its residential customers, and Washington State runs additional heat pump incentive programs on top of federal energy-efficiency tax credits. These can meaningfully offset the cost difference between a heat pump conversion and a conventional gas system replacement.
Heat pumps and larger mini-split systems usually need a dedicated 240-volt circuit, and some older Seattle homes on 100-amp electrical service need a panel upgrade before that circuit can be added safely. In Washington, that electrical work must be performed by a contractor holding a separate electrical license - an HVAC/R registration alone does not cover it.
Ask any contractor quoting a heat pump conversion to confirm in writing which specific equipment model qualifies for which rebate, the dollar amount, and whether they or you are responsible for filing the incentive paperwork. Henry can arrange three Seattle HVAC quotes so you are comparing licensed contractors instead of guessing.
Also confirm the mechanical permit and, separately, the electrical permit are both included in the quote. SDCI requires both for most heat pump conversions, and each closes with its own inspection.
Choosing a Seattle contractor for a full replacement
A full HVAC replacement is a big enough job that it is worth getting more than one bid, and worth checking the contractor's Washington L&I registration on the state's lookup tool before you sign anything.
Ask whether a Manual J load calculation was performed for your specific house, not just a rule-of-thumb estimate based on square footage. Undersized or oversized equipment causes comfort and efficiency problems that last for the life of the system.
Get the equipment make, model, and capacity, the SDCI mechanical permit, any electrical permit needed, the incentive paperwork plan, and separate parts and labor warranty terms all in writing before work starts.
For a replacement this size, comparing multiple written quotes side by side is the single best protection against overpaying or getting the wrong system for your house. Start at the Seattle HVAC hub or request quotes directly.
Typical cost ranges
| Ductless mini-split (1 to 2 zones) | $6,000 - $14,500 |
| Ductless mini-split (3 to 4 zones) | $11,000 - $19,500 |
| Full system replacement (AC + gas furnace) | $10,000 - $18,500 |
| Ducted heat pump conversion | $12,500 - $24,000 |
| Oil-to-heat-pump or oil-to-gas conversion (incl. tank decommission) | $9,500 - $22,000 |
| Electrical panel upgrade (if needed for heat pump) | $2,200 - $5,500 |
Ranges are general estimates gathered from homeowner-reported quotes, not an offer or a quote for your project.
Common questions
Is ductless or ducted better for a Seattle home?
It depends on your existing ductwork. Homes with no ducts or undersized ducts, common in pre-1950 Seattle houses, usually do better with ductless mini-splits. Homes with adequate existing ductwork are good candidates for a ducted heat pump or conventional system.
How much does a heat pump conversion cost in Seattle after incentives?
Before incentives, expect $12,500 to $24,000 for a ducted heat pump conversion. Seattle City Light and Washington State heat pump rebates plus federal tax credits can reduce that by a meaningful amount depending on the equipment chosen.
Do I need an electrician in addition to my HVAC contractor?
Often yes. Heat pump conversions typically need a new 240-volt circuit, and Washington treats electrical work as a separate license from HVAC/R contracting, so a licensed electrician needs to handle that portion.
How long does a full HVAC replacement take in Seattle?
A straightforward ducted replacement typically takes one to two days. Ductless installs with multiple zones, or oil-to-heat-pump conversions involving tank decommissioning, can take three to five days depending on scope.
What is the best time of year to replace an HVAC system in Seattle?
Spring, roughly February through May, before summer heat events drive up demand for cooling installs and before fall drives up demand for furnace and heating work.
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