Quick answer
It hinges on the delivery system you already own. A sound hydronic loop makes a like-for-like boiler swap the low-friction path — but it buys another 15–30 years of heat-only, rebate-free equipment. A heat pump adds cooling and captures Washington's 2026 incentives, and in a radiator home the smart version is usually ductless heads, not a duct-construction project. Many homes do best with the hybrid: keep the boiler, add ductless.
- Delivery is destiny: radiator homes have pipes, not ducts — converting to ducted equipment means building a duct system, often the single biggest line on the quote.
- Ductless sidesteps the conversion problem: $6,000–$9,000 single-zone, $12,000–$16,000 for a 3–5 head whole-home layout, on Eco's published ranges.
- Only the heat pump path earns 2026 money — WA HEAR (up to $8,000, income-eligible) plus utility rebates. No program pays for a new boiler.
- Boiler heat is genuinely excellent — silent, even, dust-free — and only a heat pump can also cool, filter, and dehumidify.
- The keep-the-boiler-add-ductless combo is a legitimate answer, not a compromise: the boiler carries deep winter, the heads carry shoulder seasons and summer.
At a glance
| New boiler | Heat pump (ductless) | |
|---|---|---|
| Uses your existing delivery | Yes — the hydronic loop stays | No pipes needed — wall/ceiling heads, no ducts either |
| Cooling | None — heat only | Built in — every head is air conditioning in summer |
| 2026 rebates | None | WA HEAR (income-eligible) + PSE/SCL/SnoPUD/Tacoma Power |
| Comfort character | Silent, even, radiant warmth — the reason owners love it | Warm-air zones with room-by-room control |
| Typical lifespan | 15–30 years; cast iron often longer | 15–20 years with annual service |
| Operating economics | Buys gas per therm for every BTU | 2–4 units of heat per unit of electricity |
Lifespans per manufacturer data and field experience; efficiency framing per ENERGY STAR categories. The right answer starts from your hydronic system's condition, not the equipment brochure.
What does each option cost installed in the Seattle area?
These paths aren't priced like-for-like because they aren't the same project. The boiler swap reuses your pipes; ductless reuses nothing but your electrical panel; a full ducted conversion builds a delivery system from scratch — which is why we quote it per home rather than publish a range that would mislead you.
| Option | Typical installed range | What that covers |
|---|---|---|
| Like-for-like boiler replacement | Quoted per system | High-efficiency condensing boilers vary widely with system type, venting, and hydronic condition — we price it at the home after inspecting the loop. |
| Ductless heat pump, single zone | $6,000–$9,000 | One outdoor unit, one head — cooling and shoulder-season heat for the main living space while the boiler keeps its job. |
| Ductless multi-zone (3–5 heads) | $12,000–$16,000 | Whole-home heating and cooling without touching the radiators — the full-replacement path most radiator homes actually choose. |
| Ducted heat pump + new duct system | Quoted per home | Building ducts into a house that never had them is invasive and often costs more than the equipment — we break that line out honestly on any quote. |
What changes the price
- Hydronic system condition: a sound loop and healthy radiators argue for keeping them; a failing loop changes the math toward full ductless replacement.
- Electrical capacity: ductless needs a dedicated 240V circuit per outdoor unit — panel headroom gets confirmed by load calculation before we quote.
- Zone count and head styles: wall heads cost less than ceiling cassettes; line-set runs and outdoor placement move labor.
- Rebate stack: the heat pump path draws WA HEAR (income-eligible, point-of-sale) plus your utility's rebate; the boiler draws nothing in 2026.
- Asbestos and access in older homes: pre-1960 basements sometimes add abatement or access work regardless of which path you pick.
Ranges are representative Seattle / Puget Sound installed prices, not a quote — your home's specifics set the real number. Eco gives you an upfront price before any work begins.
How do they work differently?
How a boiler heats your home
A burner heats water — not to boiling, despite the name — and a pump circulates it through radiators, baseboards, or floor tubing. Rooms warm by radiant and convective heat: no fans, no ducts, no filters, no air movement. It's the quietest, most even heat in residential use, which is exactly why radiator-home owners hesitate to give it up. What it can't do is cool, filter, or earn a rebate.
How a heat pump replaces it
A heat pump moves heat from outdoor air indoors — 2 to 4 units of heat per unit of electricity in our mild climate — and reverses in summer to cool. In a radiator home the practical version is ductless: refrigerant lines feed wall or ceiling heads room by room, no ducts required. (Air-to-water heat pumps that feed existing radiators exist, but low-temperature radiator compatibility has to be engineered per home — ask us honestly whether yours qualifies.)
Pros and cons, honestly
New boiler
Pros
- Keeps the silent, even radiant heat the house was built around
- Reuses the existing hydronic loop — low-friction replacement
- 15–30 year lifespans; simple annual service
- No electrical panel demands
Cons
- Heat only — no cooling, no filtration, no dehumidification
- Zero rebate support in Washington in 2026
- Ties the home to gas rates for decades
- Parts and expertise for older hydronic systems can be scarce
Heat pump (ductless)
Pros
- The only path that also cools — and summers here now demand it
- 2–4× the heat per unit of energy purchased
- WA HEAR + utility rebates cut the real price
- Room-by-room zoning; no duct construction in a duct-free house
Cons
- Different comfort character — moving warm air, not radiant silence
- Wall/ceiling heads are visible in the rooms they serve
- Needs panel capacity and a dedicated circuit
- Full replacement means walking away from a beloved heating type
Which one should you choose?
Choose the boiler swap when
Your hydronic system is sound, you love radiant heat, cooling is genuinely handled some other way (or genuinely unwanted), and you want the lowest-friction path back to reliable heat. It's an honest choice — just make it knowing it's rebate-free, heat-only, and commits the home to gas for another generation of equipment. If the boiler is limping rather than dead, that's the window to plan the hybrid instead.
Choose the heat pump when
You want cooling — which more Puget Sound summers demand every year — or your bills, electrification plans, or rebate eligibility push electric. In a radiator home, price the ductless multi-zone layout before any duct-construction quote: $12,000–$16,000 for 3–5 heads against a from-scratch duct system is rarely a close call. Income-eligible households can take up to $8,000 off at the point of sale through WA HEAR.
Also consider: keep the boiler, add ductless
The combo is often the best answer in the whole comparison: the boiler keeps doing what it does beautifully in deep winter, one or two ductless heads add summer cooling plus efficient shoulder-season heat, and you've effectively pre-installed half the eventual replacement. When the boiler finally dies, the decision is smaller — and until then, you gave up nothing.
The verdict, by situation
New boiler
The loyalist's low-friction swap
Right when the loop is sound, radiant heat is non-negotiable, and cooling truly isn't wanted. Priced per system after a hydronic inspection — never off a brochure.
Ductless heat pump
The full answer for most radiator homes
Whole-home heating AND cooling at $12,000–$16,000 for 3–5 heads, with the only rebate stack in the comparison — and no duct construction anywhere.
Boiler + ductless combo
The quiet overachiever
Keep the radiators, gain cooling, split the year between two systems that each do their best work. The most underrated option on this page.
Which Washington homes this fits
1920s craftsman with cast-iron radiators, Wallingford
The classic combo candidate: the boiler stays, two or three heads add cooling and shoulder-season efficiency — and Seattle City Light rebates apply to the heat pump.
Radiator home with a failing, corroded loop, Everett
When the hydronic system itself is the problem, full ductless replacement beats reinvesting in pipes — and SnoPUD pays on qualifying installs.
Mid-century rambler with baseboard hydronics, Burien
Single-story layouts take clean multi-zone designs — price the 3–4 head layout against the boiler swap and let the cooling decide it.
Radiant-floor home the owners adore, Mount Vernon
Floor hydronics are worth keeping. Service the boiler well, add a head where summer heat bites, and revisit at end of life.
Ready to compare for your home?
Get honest numbers for both options side by side — an upfront range, the considerations, and the rebates you qualify for, before any work begins.
Continue exploring
- BookDuctless mini-split services
- BookHeat pump installation
- BookHeating services
- CompareDuctless Mini-Split vs Central HVAC: The Whole-Home Decision
- CompareSingle-Zone vs Multi-Zone Mini-Split: One Head or the Whole House?
- CompareDual Fuel vs All-Electric Heat Pump: Is the Gas Backup Worth It?
- CompareHeat Pump vs Electric Furnace: The All-Electric Showdown
- GuideBoiler vs furnace vs heat pump — the three-way explainer
- GuideWashington rebates & incentives
- GuideHVAC system cost guide
- CompareAll heating & air comparisons
Common questions
Can a heat pump use my existing radiators?
Sometimes — that's an air-to-water heat pump, which heats the loop water instead of blowing air. The catch is temperature: radiators sized for a boiler's hot water may underdeliver at a heat pump's lower water temperatures, so compatibility has to be engineered per home, radiator by radiator. For most radiator homes, ductless heads are the simpler, better-supported heat pump path.
Is replacing a boiler with ductless cheaper than adding ducts?
Almost always. A 3–5 head ductless layout runs $12,000–$16,000 on our published range and touches no walls beyond the line-set penetrations. Building a duct system into a house that never had one is invasive, and that construction line regularly costs more than the heating equipment itself — which is why we quote ducted conversions per home rather than publish a number.
Are there rebates for a new boiler in Washington?
No. The federal 25C credit expired December 31, 2025, and Washington's live 2026 programs — WA HEAR point-of-sale rebates plus PSE, Seattle City Light, SnoPUD, and Tacoma Power utility programs — fund heat pumps, not boilers. If incentive money matters to your decision, it all points one direction.
Will I miss radiant heat if I switch to ductless?
Honestly: the character changes. Radiant heat is silent and perfectly even; ductless moves warm air, quietly but audibly, with the temperature control concentrated where the heads are. Most converts stop noticing within a season and consider summer cooling a more-than-fair trade — but if radiant warmth is the thing you love most about your house, the keep-the-boiler-add-ductless combo exists precisely for you.
My boiler still works. Should I wait for it to die?
A limping boiler is the best planning window you'll get. Emergency replacements get decided in a cold house under time pressure — the moment conversion options can't be properly designed. If yours is past 20 years or needing regular service, get the hybrid and replacement paths priced now, add ductless on your schedule, and let the boiler retire with dignity instead of drama.
Last updated: 2026-07-17
Sources & references
Equipment ratings, program details, and industry figures on this page come from manufacturers and primary sources, linked below. Verify program status and requirements for your home where applicable.
Equipment & efficiency
- Boiler efficiency is rated by AFUE; ENERGY STAR certifies high-efficiency models — ENERGY STAR — Boilers
- Cold-climate heat pump capacity listings, including ductless systems — NEEP — Cold-Climate ASHP List
Rebates
- WA HEAR point-of-sale rebates fund qualifying heat pumps for income-eligible households — WA Commerce — HEAR program
- Utility heat-pump rebates for PSE customers — PSE — Rebates