A boiler has all year to break. It could go in June, when you’d barely notice and the only casualty would be a lukewarm shower. It doesn’t. It waits for the first night it drops below freezing, ideally a Sunday, and ideally when you have people coming over.
So now the house is 58 degrees and falling. Someone is wearing a winter hat indoors, which is a look. And a quote for a brand-new boiler is sitting on the kitchen table, written in the time it took the water in the kettle to boil, which is more than the boiler can say.
That quote may be perfectly good. But it’s the one heating quote almost nobody compares, because comparing quotes takes days and the house is cold now. That makes it the most expensive kind of decision to get wrong: big, rushed, and in force for the next twenty-five years.
The short answer
You can usually buy yourself a few days. Do that first (there’s a list below), then get a second quote, and read both for the things a same-day proposal tends to leave out:
- How the new boiler was sized. “Same size as the old one” is not a method. It’s a tradition.
- Steam or hot water, said out loud. They are different machines, piped differently, at different prices.
- The piping right around the boiler. On a steam system, that piping decides whether the radiators heat quietly or bang like a radiator in a movie about a haunted house.
- The chimney. A new boiler can leave your water heater venting alone up a flue that was built for two.
- Startup and cleaning. A combustion test, and on steam, skimming the new boiler.
- The permit, removal of the old boiler, and anything wrapped in old white insulation.
None of these missing is proof of anything. Each one is a question.
First, buy yourself a day
Before anyone sells you a boiler, it’s worth five minutes making sure you need one. This isn’t a repair guide, and anything involving gas or a hot boiler is a job for a pro. But a surprising number of “dead” boilers are really one of these:
- The emergency switch. In a lot of older houses there’s a switch at the top of the basement stairs, often with a red plate, that looks like a light switch. It shuts the burner off. It also gets flipped by people looking for the basement light. Check it.
- The thermostat. Fresh batteries, set to heat, set higher than the room. We know. Check anyway.
- The water level, on a steam boiler. There’s a small glass tube on the side showing the water inside. If it’s empty, a safety control has done its job and shut the burner off. Do not add water to a hot boiler with an empty glass. Let it cool and call someone. Cold water on a hot cast iron boiler is how a bad night becomes a much more expensive one.
- The reset button, on an oil burner. Press it once. If it doesn’t start, stop. Pressing it five times is not five times the fix. Each press can pump more oil into the chamber, and that ends with a cleaning crew.
- If you smell gas, none of the above applies. Leave the house and call the gas company from outside.
If it’s truly down, a repair visit to get it running for a week is often worth paying for even when it’s going to be replaced anyway. A week of heat buys you a second quote. Meanwhile, plug space heaters straight into the wall (not a power strip), keep them three feet from anything that can burn, and open the cabinets under the sinks on outside walls so the pipes get some of the warm air too.
Why it works that way
Sizing: the old boiler is not a measuring tape
Plenty of old boilers are much bigger than the house needs. They were sized generously decades ago, and since then somebody insulated the attic, replaced the windows, and took out two radiators to make room for a bookcase. Replacing it “same size” repeats that guess.
How a boiler should be sized depends on what it feeds:
- Hot water: from the house’s heat loss, the same kind of load calculation a furnace should get.
- Steam: from the radiators. Every radiator in the house gets measured and added up, and the boiler is matched to the total. It’s tedious, it involves a tape measure and a chart, and it’s the honest way. A quote that says the radiators were counted is telling you something good about the person who wrote it.
Steam and hot water are not two flavors of the same thing
A hot-water system pumps warm water around a loop. A steam system boils water and lets the steam rise to the radiators on its own. Different boiler, different controls, different piping, different price. Some old houses have steam radiators that look exactly like hot-water ones, so if your quote doesn’t say which system you have, ask. If it says the wrong one, ask faster.
On steam, the piping next to the boiler matters as much as the boiler
Every steam boiler comes with the manufacturer’s instructions for the piping right above it: how high it rises, how it connects back. Get it wrong and you get wet steam, water hammer, and radiators that clang at 5 a.m. like they’re trying to send you a message. A good quote describes this piping, or says the manufacturer’s piping diagram will be followed. A quote that just says “connect to existing” may be planning to reuse piping that was built for a different boiler.
A brand-new steam boiler also needs skimming after it’s installed: the oil from the factory gets flushed off the water’s surface. Skip it and the water level bounces around in the glass like it’s had too much coffee. It’s a line item, or at least a sentence, and it’s easy to leave out.
On hot water, high efficiency has fine print
A condensing boiler (the high-efficiency kind, usually wall-hung) gets its efficiency by squeezing heat out of its own exhaust, and it only does that well when the water coming back to it is fairly cool. Big old cast iron radiators are good at that. Baseboard that needs very hot water is less so. A condensing boiler also needs new plastic venting, a drain for the acidic water it makes, and something to neutralize that water. Good quotes list all three.
The chimney you forgot you share
In a lot of houses, the old boiler and the water heater share one chimney. Take the boiler out of that chimney (a new high-efficiency boiler often vents out the side wall instead) and the water heater is left venting up a flue sized for two appliances. That can mean poor draft and a chimney liner nobody priced. The quote should say what happens to the water heater’s venting. “Nothing” is an answer, as long as someone decided it.
The white stuff on the old pipes
Older boilers and pipes are often wrapped in white insulation that may contain asbestos. If it has to be disturbed, it usually means testing and a licensed removal crew, generally a separate company and a separate bill. It’s not a reason to panic. It is a reason to know before the old boiler is in pieces on the basement floor.
What we can actually see in the numbers
Not much yet, and we’d rather say so. We have nine homeowner-submitted boiler quotes on file, and every one is a hot-water boiler. Zero are steam. None of them is marked as an emergency, so we can’t tell you whether a same-day quote costs more. We can’t see it either way.
Here’s what the nine show. The middle one came in at $10,100. Five of the nine landed between $8,350 and $13,600. The low end was $7,650. The high end was $29,750, and that one wasn’t just a boiler: it was a combination boiler that also makes the house’s hot water, with two heating zones re-piped. Same word, “boiler,” at the top of the page, very different job underneath. That’s the whole reason to read the scope before the price.
If you’re holding a boiler quote this winter, especially a steam one, you are holding the thing we have the least of. Running it through the Quote X-Ray gets you a reading of what it says and what it never mentions, and, if you opt in, it becomes one of the rows the next person compares against. It’s free, and it takes about as long as the kettle.
What to ask
- “How did you size it?” On steam: “Did you measure the radiators?” On hot water: “Did you do a heat-loss calculation?”
- “Is this priced for steam or hot water?” Then check that it matches what’s in your basement.
- “What happens to the piping around the boiler?” On steam, ask whether it will follow the manufacturer’s piping diagram.
- “What happens to the water heater’s venting?”
- “What’s included at startup?” A combustion test, and on steam, skimming.
- “Who pulls the permit, and who takes the old boiler out?” And, if the old pipes are wrapped in white: “Who deals with that?”
What a bad answer sounds like
“Same size as the old one, you can’t go wrong.” You can, specifically by buying the old guess again.
“Steam, water, it’s all the same boiler.” It isn’t, and the person who installs it knows that better than we do.
“We’ll figure out the piping when we get there.” That’s the part that decides whether the thing works quietly for twenty-five years. It’s worth figuring out before.
“This price is only good today.” Maybe. But the boiler cost the same yesterday and will cost about the same on Thursday. A quote that can’t survive a weekend of you thinking about it is telling you something about the quote.
One to look at yourself
Go stand in front of your boiler. Look for the small glass tube on the side. If there’s one, you have steam, and you’re now ahead of some of the quotes we’ve read. Then look up. Count the pipes coming off the top and follow them as far as you can. That tangle is the near-boiler piping, and it’s about to become the most important line on your quote.
Where this stops
Nine quotes is a sample, not a market, and we won’t pretend it’s more. This post can tell you what to look for on a boiler quote. It can’t tell you whether yours is priced right, whether your old boiler can be saved, or what your house needs. That takes someone standing in your basement. It might as well be the second someone, not just the first.
Data: the nine homeowner-submitted boiler quotes in the Read the Nameplate database (scope type “boiler”, source “user”), pulled October 29, 2026. Quotes are self-reported by homeowners; the high one is called out above because its job is much bigger than the rest.