Thousands of Detroit homes still heat with a boiler and cast iron radiators. A well-kept boiler gives even, quiet heat for decades. When it does need replacing, a new boiler is usually simpler than switching to a furnace.
Price ranges on this page are national figures published by HomeGuide for 2026. They are not our quotes. Your house, the equipment you choose, the venting and the ductwork move the real number up or down. Last checked October 2026.
How much does a new boiler cost?
A new boiler costs $3,200 to $9,000 installed on average, with a national average of $6,100, by HomeGuide's boiler replacement page. Standard-efficiency boilers run $2,200 to $7,000 and high-efficiency boilers $4,000 to $10,000.
| Fuel | Unit only | Installed |
|---|---|---|
| Gas | $1,400 to $5,600 | $4,000 to $9,000 |
| Oil | $1,700 to $6,500 | $3,300 to $9,000 |
| Electric | $1,000 to $6,000 | $1,800 to $8,000 |
| Propane | $1,800 to $4,000 | $2,800 to $7,500 |
Steam boilers cost more than hot water boilers as units: $1,800 to $6,000 against $1,200 to $4,000, by the same page. Old radiators that need replacing cost $250 to $500 each.
How do I know my old boiler needs to be replaced?
An old boiler needs to be replaced when it leaks from the body, keeps failing, or can no longer be made safe. Age alone is not enough. HomeGuide gives an average boiler life of 10 to 20 years and says some cast iron boilers last 30 years or more, and it flags boilers over 15 years old as replacement candidates.
A 40-year-old boiler that still runs is not automatically a problem, but it is worth a combustion test and a look at the heat exchanger and controls. Planning a replacement in summer is far better than an emergency swap in January.
Should I replace my boiler or switch to a furnace?
For most Detroit radiator homes, replacing the boiler is better than switching to a furnace. A switch to a furnace means running ducts to every room through plaster walls and floors. That is a large job, and the radiant heat many owners like is lost.
Switching can make sense when you also want central air and are opening walls anyway. Ductless mini-splits are another way to add cooling while keeping the boiler.
Why are my radiators cold at the top?
On a hot water system, a radiator that is cold at the top has trapped air, and you need to bleed it. Open the small valve at the top with a radiator key and a rag until water comes out, then close it. Check the boiler pressure afterwards.
If radiators need bleeding often, the system may be losing pressure or the expansion tank may have failed. Steam radiators are different. They have a vent that lets air out on its own, and a cold steam radiator usually has a bad vent.
Why do my steam radiators bang?
Steam radiators bang when water is trapped in the radiator or pipes and steam slams into it. The radiator may need to tilt slightly toward its valve, the valve may be partly closed, or a pipe may have sagged. Steam radiator valves should be fully open or fully closed, not in between.
Banging in a hot water system usually points to air or a failing pump instead. We trace the cause and fix the pitch, vents or pump.
How often should a boiler be serviced or flushed?
A boiler should be serviced once a year, before the heating season. HomeGuide lists routine boiler service at $70 to $350 and a flush and descale at $150 to $600, by its national figures.
Steam boilers also need their water level and low-water cutoff checked during the winter, and many need a periodic blowdown. Hot water systems are flushed when sludge or scale builds up, not on a fixed schedule. We tell you what your system needs.
Is a high-efficiency condensing boiler worth it?
A condensing boiler is usually worth it on a hot water system, where it can reach its efficiency because the water coming back is cool enough to condense. HomeGuide lists high-efficiency boilers of 90% to 95% AFUE or more at $4,000 to $10,000 installed, against $2,200 to $7,000 for standard models, by its national figures.
Steam systems cannot use a condensing boiler, so a steam home stays with a steam boiler. Large old cast iron radiators often let a condensing boiler run at lower water temperatures, which helps its efficiency.
Can I get central air in a radiator house?
Yes. The common choices are ductless mini-splits, a small-duct high-velocity system, or an attic air handler with short duct runs to the upstairs rooms. Each keeps the boiler and radiators for heat. See our AC replacement cost page for the national price ranges.
The only way to get a real price for your home is an on-site visit and a written quote. Call or text (313) 488-2188.