Should I repair or replace my boiler?

Repair your boiler when it is under about 15 years old, the heat exchanger is sound and the fault is one replaceable part such as a sensor, igniter, pump or valve. Start pricing a replacement when it is past 15 years, needs repairs every season while your fuel bills climb, or the heat exchanger has cracked or leaked outside its warranty. The best way to decide is to have one licensed technician quote both, in writing, on the same visit.

Start with the boiler's age

Age is the first filter. ENERGY STAR lists a furnace or boiler more than 15 years old as a sign it may be time to call a contractor about replacement^[1]. Navien says much the same: both condensing and non-condensing boilers can have a service life of around 15 to 20 years^[3]. That range is not a deadline. Navien says lifespan depends on maintenance, the quality of the water passing through the boiler and how well the system is designed to work with it^[2], and that a well-maintained boiler in a properly designed and installed system could last up to 20 years or longer in some cases^[2].

So a 7-year-old boiler with a failed igniter is a repair. A 25-year-old boiler with the same failure is still often a repair, but it is the moment to get a replacement price too, so you are not choosing in an emergency next January.

Then look at what failed

Replaceable parts. Sensors, igniters, flame rods, circulator pumps, zone valves, expansion tanks, relief valves and control boards are replaced routinely. Fixing one usually makes sense unless the boiler is old and has needed several of them recently.

The heat exchanger. This is the part that decides most cases. Minerals from constant fresh make-up water can build up in the heat exchanger, reduce heat transfer, overheat it and cause it to fail^[4]. On a newer boiler, check the warranty first. Navien's NHB-H warranty, for example, covers the heat exchanger for 10 years in a single-family home, then makes the owner pay a rising share of its list price, 30% in year 11 up to 70% in year 15, with labour not included^[4]. Out of warranty, the decision turns on the part's price, the labour to drain the system and fit it, and the age of everything else on the boiler, so ask for a repair price and a replacement price in writing before you decide.

Repeated failures. ENERGY STAR also flags equipment that needs frequent repairs while your energy bills go up^[1], and rooms that are too hot or too cold, which can come from the equipment, the distribution system or poor insulation^[1]. A run of service calls is worth weighing even if each one was cheap.

Efficiency: what a new boiler would save

Older boilers waste more of the fuel you buy. Navien notes that traditional boilers have an AFUE of up to 80%, so up to 20% of the fuel is lost, while its condensing gas boilers reach up to 95%^[3]. ENERGY STAR certified gas boilers are rated at 90% AFUE or greater and oil boilers at 87% or greater^[5], and ENERGY STAR says a certified boiler is 5% more efficient than a new, standard model^[1]. The savings are largest when you are replacing an old, low-efficiency boiler in a house with a long heating season.

ENERGY STAR's advice is to compare cost, energy efficiency and warranties^[7], and it warns that the lowest price may not be the best deal if it is not the most efficient, because your energy costs will be higher^[7].

What replacement involves that a repair does not

A replacement is a bigger job than swapping a boiler in the same spot, and the quote should reflect that:

• Venting. A non-condensing boiler must be vented through a proper chimney or flue because its exhaust is extremely hot.^[3] A condensing boiler can be vented in PVC or polypropylene, but it needs a drain line for its acidic condensate^[3]. Moving from one to the other changes the venting and drainage work.
• Sizing. Weil-McLain says your heating professional should do a heat-loss estimate based on the size and construction of your home before recommending a boiler size and model^[6]. ENERGY STAR agrees that a contractor should size the system based on the size of the house, its insulation and its windows^[7]. As ENERGY STAR puts it, "A bigger system isn't always better"^[7].
• Permit and inspection. Virginia's building code requires a permit before installations or alterations involving mechanical systems or fuel supply systems, or any equipment the code regulates^[8], and its exemption for replacing mechanical appliances covers only equipment that is not fueled by gas or oil^[8]. So a gas or oil boiler replacement needs a permit. The application can be made by the owner, the owner's agent or the contractor^[8], so settle in the quote who will apply.
• Incentives. The federal energy-efficient home improvement credit covered improvements made through December 31, 2025^[9]. Ask about current utility rebates, but do not let an offer you cannot verify drive the decision.

For what all of that adds up to, see how much a new boiler costs in Virginia, and for the repair side, how much boiler repair costs in Virginia.

Questions to ask the technician

• How old is this boiler, and what is the condition of the heat exchanger?
• What failed, what does the repair cost, and what is the warranty on that part?
• What else on this boiler is likely to need work in the next few years?
• What would a correctly sized replacement cost, including venting, permit and removal of the old one?
• What efficiency would the replacement have, and roughly what would it save on fuel?

When to call a licensed pro

Both choices are licensed work. Virginia's tradesman rules define HVAC work to include the installation, repair and maintenance of "steam and hot water heating systems, boilers"^[10], and no one may work as a tradesman unless licensed^[11]. Our guide to who can service a gas boiler in Virginia explains the licence types, and you can check any business on DPOR's License Lookup^[12]. To compare businesses that install boilers, browse boiler and radiant heating pros or more HVAC repair answers.

To get a repair price and a replacement price on the same visit, describe your boiler once and compare quotes from licensed technicians.