Quick answer
These three don't just make heat differently — they deliver it differently, and delivery is destiny in this comparison. Radiator homes and ducted homes are set up for different machines, and converting from one to the other costs more than any of the equipment. The practical questions: What does your house have today? Do you want cooling? And how long will you own it?
- Boiler = hot water through radiators or floors. Furnace = hot air through ducts. Heat pump = moved heat, air delivery, plus cooling.
- The delivery system (pipes vs ducts) usually decides the replacement — converting is the expensive part.
- Boiler owners who want AC don't have to abandon the boiler: keep it for heat, add ductless for cooling. It's a common and sensible combo.
- Only the heat pump earns Washington rebates (HEAR income-qualified, plus PSE), and only the heat pump cools.
Last updated: 2026-07-16 · Written & reviewed by the Eco field team
Boiler vs furnace vs heat pump at a glance
| Boiler | Furnace | Heat Pump | |
|---|---|---|---|
| Delivers heat via | Hot water — radiators, baseboard, radiant floor | Hot air — ducts | Warm air — ducts or ductless heads |
| Cooling | No | No — needs separate AC | Built in |
| Feel | Silent, even, no blowing air | Fast, hot blasts | Steady, even warmth |
| Air filtration | None — no airflow | Yes, at the filter | Yes (ducted) / per-head (ductless) |
| Fuel | Gas (most here) | Gas | Electricity |
| Typical lifespan | 15–30 years (cast iron often longer) | 8–10 years (PNW typical) | 15–20 years with annual service |
| Rebates (2026) | None | None | WA HEAR + PSE |
| Best fit | Radiator/radiant homes staying hydronic | Ducted gas homes on a budget | Most homes ready for efficiency + cooling |
Delivery is destiny: the conversion problem
Here's what most comparisons skip. If your radiator home's boiler dies, replacing it with a furnace or ducted heat pump means building a duct system inside a house that was never designed for one — invasive, expensive, and often the single biggest line item on the quote. Likewise, a ducted home has no pipes for a boiler. That's why like-for-like replacement is the default path, and why the interesting exceptions are the ones worth planning: a radiator home adding ductless heads (keep the boiler, gain cooling and efficiency), or a ducted gas home stepping to a heat pump on its existing ducts.
The boiler owner's dilemma — and the combo answer
Boiler heat is beloved for a reason: silent, dust-free, beautifully even. What it can't do is cool, filter, or qualify for rebates — and summers here now demand cooling more years than not. The honest answer for many radiator homes isn't replacement, it's addition: keep the boiler doing what it does best, and add a ductless heat pump for cooling that also happens to provide efficient shoulder-season heating. The two systems split the year between them, and you never gave up the radiators. When the boiler eventually dies, you'll already have half the replacement installed.
How does each one heat, in one paragraph each?
Boiler: a burner heats water (not to boiling, despite the name), a pump circulates it through radiators, baseboards, or floor tubing, and the rooms warm by radiant and convective heat. No fans, no ducts, no filters — just quiet, even warmth that older Seattle homes were literally built around. Furnace: gas burns in a heat exchanger, a blower pushes air across it, ducts deliver it. It's the dominant system in post-war housing, it heats fast, and its ductwork doubles as the delivery system for air conditioning — which is a bigger advantage than it sounds. Heat pump: refrigerant absorbs heat from outdoor air and releases it inside, delivering 2–4 units of heat per unit of electricity. It uses ducts if you have them or ductless heads if you don't — and it reverses in summer to cool.
When does each one win?
Boiler wins when you have radiators or radiant floors you love, the hydronic system is sound, and cooling is handled some other way (or genuinely not wanted). Furnace wins when your home is ducted for gas, the budget is tight, and you need dependable heat without changing anything else. Heat pump wins when you want cooling, your bills matter long-term, you're on electric resistance today, or rebates change your math — which, in Washington right now, they often do.
Pros and cons, honestly
Boiler (hydronic)
Pros
- Silent, even, duct-free warmth — no blowing air, no filters to change
- 15–30 year lifespans; cast iron often longer
- Older Seattle homes were built around it
Cons
- No cooling, no air filtration
- No Washington rebates apply (2026)
- Parts and expertise for older systems can be scarce
Furnace (forced air)
Pros
- Fast heat; the dominant post-war system
- Its ductwork doubles as the AC delivery system
- Lowest-friction replacement in a ducted gas home
Cons
- 8–10 year PNW-typical lifespan
- Heating only — cooling needs separate equipment
- No Washington rebates apply (2026)
Heat pump
Pros
- 2–4 units of heat per unit of electricity — the efficiency leader in our climate
- The only option that also cools
- WA HEAR (income-qualified) + PSE rebates; 15–20 year lifespan with annual service
Cons
- Needs ducts or ductless heads — the delivery system drives the install
- Radiator homes need a specialized air-to-water unit or the add-ductless combo
The conversion quote trap
The most expensive line on a heating quote is often not the equipment — it's changing the delivery system. Building ducts into a radiator home, or piping a hydronic loop into a ducted one, regularly costs more than the machine itself. If a quote glosses over that line, ask for it broken out. Like-for-like replacement, or the keep-the-boiler-add-ductless combo, usually beats a forced conversion.
The verdict, by situation
Boiler
Keep it if your house was built around it
Sound radiators and piping mean a new boiler drops in with the least invasion and often the least cost. Want cooling too? Add ductless heads — don't abandon the radiators.
Furnace
The low-friction swap for ducted gas homes
If the ducts exist and the budget is tight, a like-for-like furnace swap is dependable heat with nothing else changed — and the ducts stay ready for AC or a heat pump later.
Heat pump
The efficiency-and-cooling answer
2–4 units of heat per unit of electricity, built-in summer cooling, and the only Washington-rebated path. On existing ducts, it's the natural next step from a gas furnace.
Which Washington homes this fits
1920s Craftsman with radiators (Wallingford, Queen Anne)
Delivery is destiny: keep the hydronic system if it's sound. The classic upgrade is boiler-plus-ductless — silent radiator winters, efficient cooling in the heat.
Post-war ducted rambler (Everett, Shoreline)
The duct tree is the asset. A furnace swap is the budget path; a ducted heat pump on the same ducts is the efficiency-plus-cooling path with rebates behind it.
Radiator home whose boiler just died
A new boiler into sound piping is usually the least invasive, least expensive answer — a forced duct conversion is the biggest line item on any competing quote.
Electric-resistance home with neither pipes nor ducts
Ductless heat pump heads skip the delivery problem entirely — no ducts required, room-by-room control, and the biggest bill cut available.
How we build this guidance
- We service all three — boilers, furnaces, and heat pumps — across Seattle and Everett, including the older hydronic systems many companies won't touch.
- Recommendations follow your home's delivery system first, because that's where the real costs live.
- We'll tell you when keeping your boiler is the right answer — even when a full conversion would be the bigger sale.
Methodology: Lifespan and efficiency figures from manufacturer data and field experience; rebate details verified against program sources as of July 2026.
Ready for the next step?
Get a free estimate for your actual house, not a hypothetical one — honest numbers and rebate eligibility checked before any work begins.
Continue exploring
- Learn: Furnace vs heat pump — which should heat your Puget Sound home? →
- Learn: Ducted vs ductless vs mixed — which layout fits your home? →
- Learn: How do heat pumps work? →
- Learn: Washington HVAC rebates explained →
- Evaluate: Heat pump vs gas furnace — the decision framework →
- Compare: Furnace repair vs replacement — how to make the call →
- Compare: Furnace vs air handler — which indoor unit? →
- Book: Heating estimates and service →
Common questions
My boiler died. Do I have to switch to a furnace or heat pump?
No. If the radiators and piping are sound, a new boiler drops into the existing system — usually the least invasive and often the least expensive path. Conversions make sense in specific situations, not as a default.
Can a heat pump work with my radiators?
Standard air-source heat pumps heat air, not radiator water. Air-to-water heat pumps that drive hydronic systems exist and are improving fast, but they're a specialized fit — sizing, radiator temperatures, and insulation all matter. Ask before assuming either way.
Which is cheapest to run?
In our climate, generally the heat pump, thanks to 2–4 units of heat per unit of electricity. Gas boilers and furnaces land close together, with the edge shifting on fuel prices and system condition. What you're switching from matters more than brand brochures.
Why do boilers last so long?
Fewer moving parts and no air handling — mostly a burner, a pump, and sealed water. Cast-iron boilers running 25–30 years aren't rare. The flip side: when they do go, parts and expertise for older systems can be scarce.
Does a boiler home need duct cleaning or filters?
No ducts, no filters — nothing to clean or change. That's part of the appeal for allergy households. The tradeoff is that nothing is filtering the air, either — a consideration if smoke season or dust is a concern.
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.
Heating system types
- Furnaces and boilers: how each works and efficiency considerations — US DOE Energy Saver — Furnaces and Boilers
- Heat pump systems overview and efficiency — US DOE Energy Saver — Heat Pump Systems
Washington rebates
- HEAR: income-qualified heat pump rebates administered by Washington State (funds first-come, first-served) — WA Dept. of Commerce — Home Electrification and Appliance Rebates (HEAR)
- Puget Sound Energy residential heat pump rebates — Puget Sound Energy — residential rebates
Equipment lifespan (our published data)
- Puget Sound service-life figures: furnaces 8–10 years, central ACs 12–15, heat pumps 15–20+ with annual service — Eco — How Long Does an HVAC System Last in the PNW?