Boiler repair and replacement: a guide for homes with radiators

Updated November 10, 2026 · KeystoneProGuide editorial team

What should you know if your home has a boiler?

That it is a different machine from a furnace, with different rules. The U.S. Energy Information Administration describes a steam or hot-water system as one that supplies steam or hot water from a boiler to radiators, baseboard units, convectors or heating pipes, and a central furnace as one that provides warm air through ducts to the rooms. The Census Bureau's profiles count fuel, not equipment, so there is no published figure for how many Pennsylvania homes have boilers. What the Census Bureau's Pennsylvania profile does show is the age of the stock: 25.0 percent of the state's housing was first built in 1939 or earlier.

How efficient should a new boiler be?

ENERGY STAR certifies gas boilers with an Annual Fuel Utilization Efficiency of 90 percent or more, about 6 percent above the federal standard, and oil boilers at 87 percent or more, about 1 percent above it. It credits three features for the gain:

• Electronic ignition, so there is no pilot light burning all the time.
• Newer combustion technology that extracts more heat from the same fuel.
• Sealed combustion, which draws outside air to the burner, reducing drafts and improving safety.

It estimates that a certified gas boiler saves about $780 over its life, and an oil boiler $200. Its guidance on when to consider replacement treats boilers like furnaces: more than 15 years old, especially with frequent repairs and rising bills, and it says an ENERGY STAR boiler is 5 percent more efficient than a new standard model.

Does Pennsylvania inspect home boilers?

Not in an ordinary house. Pennsylvania's Boiler and Unfired Pressure Vessel Law requires the Department of Labor and Industry to approve the installation of boilers and inspect them, but its Boiler Division lists boilers in a single-family residence as exempt from its inspection, as long as no business is located in the home. Boilers in apartment buildings with four or fewer units are exempt too. Water heaters are exempt below set limits, including a heat input of 200,000 BTU per hour and a capacity of 120 gallons.

The exemption is from the boiler law only. The department says exempt work may still be subject to the Uniform Construction Code, so a local permit is still generally needed to replace a boiler, and an emergency replacement can go first if the application follows within 3 business days. In Philadelphia, the city's mechanical permit page notes that boiler installations are regulated by the state Department of Labor and Industry; ask L&I which permits it needs for your job.

If you run a business from your home, the exemption may not apply. The Boiler Division's phone number is 717-214-4319.

What safety checks does a boiler need?

The same yearly inspection as any fuel-burning heater. The Consumer Product Safety Commission names boilers in its call for a yearly professional inspection of fuel-burning heating systems, along with chimneys, flues and vents. The U.S. Environmental Protection Agency lists worn or poorly adjusted and maintained boilers among the household sources of carbon monoxide, along with flues that are blocked, disconnected or leaking, and advises having the central heating system and its flue and chimney inspected and tuned up every year.

When a new high-efficiency boiler replaces an old one, ask how it will be vented, and what will happen to the old chimney connection if the new unit vents another way.

What does a boiler cost?

National cost surveys give these ranges. HomeAdvisor puts boiler replacement at $3,700 to $8,300 on average, rising to $12,000 for high-efficiency models, and gives $2,800 to $9,000 for a gas boiler, $4,800 to $9,000 for oil and $1,800 to $8,000 for electric. It says the total depends on the heating capacity and the type of system. No survey publishes a Pennsylvania figure.

If a boiler fails in winter and the household cannot afford it, Pennsylvania's LIHEAP Emergency Services program lists repair of hot water heating systems, heating system repair and replacement of an unrepairable system among its services for eligible households, along with thawing frozen heating pipes. Apply through your county assistance office.

How do you add air conditioning to a house with radiators?

Without ducts, the main route ENERGY STAR describes is a ductless mini-split heat pump. It names older homes with no ductwork, heated by radiators or baseboards, that have never had central air as one of the situations where mini-splits are used, and describes them as an alternative to radiator heat and a replacement for window air conditioners. Because a mini-split is a heat pump, it heats as well as cools.

ENERGY STAR also says that if you have both a heat pump and a boiler, you should use the heat pump year-round, because it is more efficient, even in winter. That makes a mini-split a way to take part of the heating load off an oil or gas boiler, with the boiler carrying the house on the coldest days.

What should you ask a boiler contractor?

1. Is the boiler repairable, and what exactly failed?
2. What AFUE does the replacement have, and is it ENERGY STAR certified?
3. How will the new boiler be vented?
4. Who is getting the local permit?
5. Will you check the radiators, valves and expansion tank as part of the job, and what would any extra work cost?

The ages and prices that frame the decision are in repair or replace, and the mini-split option is covered in the mini-split guide. Contractors are listed on the HVAC contractors directory page.

Sources

1. Boilers, ENERGY STAR
2. When is it time to replace?, ENERGY STAR
3. Boilers and Unfired Pressure Vessels, Pennsylvania Department of Labor and Industry
4. Get a Mechanical Permit, City of Philadelphia
5. 34 Pa. Code § 403.62. Permit requirements and exemptions., Commonwealth of Pennsylvania (Pennsylvania Code)
6. Home Heating Equipment, U.S. Consumer Product Safety Commission
7. Carbon Monoxide's Impact on Indoor Air Quality, U.S. Environmental Protection Agency
8. How Much Does It Cost to Install or Replace an HVAC System?, HomeAdvisor
9. Pennsylvania LIHEAP Emergency Services Program, Pennsylvania Department of Community and Economic Development
10. Ductless Heating & Cooling, ENERGY STAR
11. Air-Source Heat Pumps, ENERGY STAR
12. 2020-2024 ACS 5-Year Narrative Profile: Pennsylvania, U.S. Census Bureau
13. RECS Terminology, U.S. Energy Information Administration