The difference in one line each
| Furnace | Boiler | |
|---|---|---|
| Heats | air | water, or steam |
| Delivers through | ducts and vents | radiators, baseboards or a floor |
| Can also cool | yes, sharing the ducts | no |
| Per-room control | only by closing vents | a thermostat per area |
| Noise | a fan | none |
| Average installed | $4,800 | $6,100 |
$1,300 between the averages, our subtraction, from two Fixr guides updated on the same day. The ranges are $2,800 to $7,500 for a furnace and $3,000 to $8,500 for a boiler.
The framing that actually decides it
This Old House splits any heating system into three parts: a heat source, a distribution system, and controls.
Our reading, marked as ours, and it is the point of this page. Furnace and boiler are both heat sources. The thing people call the choice is really a choice of distribution, and the distribution is the part you already own. Ducts cannot carry hot water and pipes cannot carry warm air. So in a house that already has one of them, the $1,300 difference between the two machines is not the number that matters; the cost of putting in the other distribution system is.
Fixr says the same thing from the practical end: a furnace requires room for ductwork, and if you have no basement or attic to run it through, another system may be the better option, while a boiler system requires water piping installed throughout.
So the honest answer to "furnace or boiler" is usually "whichever one your house is already plumbed or ducted for". The exception is new construction, or a gut renovation where the walls are open anyway.
What each one is better at
Fixr's list, with the furnace advantages first:
- Lower installation cost, which its own cost guides bear out at $4,800 against $6,100.
- Faster to install. Fixr says a furnace install takes only a few hours.
- No water in the system, so no leak risk and nothing to freeze in a power cut.
- Heats a cold house quickly.
- Shares its ducts with central air conditioning.
And the boiler:
- Evenly distributed, pleasant warmth.
- Silent, because there is no fan.
- Per-area thermostats, so a seldom-used guest room can be turned down on its own.
Against that, a boiler costs more to install and cannot double as a source of air conditioning.
One note on the source. Fixr's article has its pros and cons lists scrambled: under the furnace's "Cons" heading it lists three items that are plainly advantages, including that there is no risk of water leaks and that a furnace heats a cold home quickly. We have put them where they belong rather than reproducing the error, and we are saying so rather than quietly correcting a source.
The air conditioning question
This is the part that turns a $1,300 difference into a much larger one.
A furnace shares its ductwork with central air. A boiler has no ducts, so cooling has to be bought separately, and that means either ducts installed from scratch or a ductless system.
Our central air page prices the ducted option and our mini split vs central air page prices the alternative for a house with no ducts, which is the situation every boiler house is in.
Our conclusion: if you want cooling and you are genuinely free to choose, the furnace side of the comparison is cheaper twice over. If you already have a boiler and want cooling, the question is not furnace against boiler at all, it is which cooling system suits a house with no ductwork.
Running and maintaining them
Fixr puts the operating cost down to three things: the AFUE efficiency rating, fluctuating fuel prices, and how warm you keep the house.
On maintenance it draws a clear distinction: boilers need no more than a yearly inspection and cleaning by a professional. Fixr's boiler guide prices that annual service at $200 to $500. Our maintenance page covers what the forced-air equivalent costs, and our boiler repair page explains why the published "boiler service" averages mix that annual visit with actual repairs.
Our note, marked as ours: a forced-air system has a filter that needs changing and ducts that leak, neither of which a boiler has. A boiler has water in it, which a furnace does not. Neither is maintenance-free and the published figures do not make one obviously cheaper to keep.
If you are changing fuel at the same time
Fixr's boiler guide adds $500 to $2,500 for piping, radiator or gas line work when converting from one fuel type to another. That is on top of the machine, and it is the kind of line that turns a like-for-like comparison into a renovation.
Our boiler replacement page and furnace page have the full figures for each, and each furnace fuel is priced separately on our gas, electric, propane and oil pages.
And the third option
This Old House lists four heat sources, not two: furnaces, boilers, heat pumps and electric resistance heating. A heat pump can replace a furnace in a forced-air system, or go in as a ductless unit, and the air-to-water kind can feed the pipes a boiler used to.
Our view: if you are replacing a heat source and the distribution stays, a heat pump belongs in the comparison on both sides of this page, not only the furnace side. Our heat pump vs furnace page prices it against the furnace, and our how a heat pump works page explains the air-to-water type that suits a boiler house, along with the output temperature limit that decides whether it will work with your existing radiators.
Before you decide
- Look at what is on your walls. Radiators or vents answers the question for almost every existing house.
- Ask what the other distribution system would cost, not just the other machine, before treating this as an open choice.
- Decide about cooling first. It is the single factor that moves the most money.
- If you are keeping the distribution, price a heat pump too. It fits either side.
- If you are changing fuel, add $500 to $2,500 for the pipework before comparing quotes.
Sources
- Fixr, Furnace vs. Boiler, What's the Difference?, updated March 5, 2024 (how each works, zoning and distribution, the pros and cons lists, the maintenance comparison, the ductwork and piping requirements)
- Fixr, Furnace Replacement Cost, updated January 28, 2026 (the $2,800 to $7,500 range and $4,800 average, lifespans by fuel type)
- Fixr, How Much Does a New Boiler Cost?, updated January 28, 2026 (the $3,000 to $8,500 range and $6,100 average, labor, the annual service cost, the fuel conversion cost)
- This Old House, The Basics of Home Heating Systems, updated October 8, 2024 (the three components of a heating system, forced air against radiant, and where each suits)
Price figures are national US ranges from the sources above as of the date shown. Your local price depends on labor rates, permits and site conditions. Read how we get our numbers.