Repair or replace your boiler? How long a boiler lasts, the 40 per cent rule and the sums per repair

Short answer: a boiler lasts 15 years on average, and 18 to 20 years with annual servicing. After 15 years, parts become scarce and efficiency drops. Repairing is worthwhile as long as the repair costs less than 40 per cent of a new boiler and the boiler is less than 12 years old. So a pump of € 250 or a sensor of € 40 is almost always worth replacing; a heat exchanger of € 600 to € 900 or a PCB of € 300 to € 500 on a 13-year-old boiler is not. Also factor in efficiency: a 15-year-old boiler uses 10 to 15 per cent more gas than a new one; at 1,200 m³ a year that is 120 to 180 m³, and what that costs depends on your energy prices. A new combi boiler typically costs € 1,800 to € 2,450 installed.

How long does a boiler last?

Manufacturers count on 15 years; in practice we see 20-year-old boilers that still run well and 10-year-old boilers that are worn out. The difference comes down to four things. Servicing: a boiler that is serviced every year keeps a clean heat exchanger, good seals and correct combustion; skipped servicing is the main cause of early failure. Water quality: hard water and frequent topping up cause limescale in the heat exchanger; iron particles from old radiators wear out the pump, and a magnetic filter catches them. Running hours and short cycling: a boiler that is too large for the home switches on and off frequently and wears twice as fast as a boiler that modulates steadily. Range and year of manufacture: top models have a cast aluminium or stainless steel heat exchanger with a 10 to 25-year warranty; entry-level models 5 years.

Age	What to expect	Advice in case of a fault
0 to 5 years	Manufacturer's warranty; faults are usually sensors, ignition or the condensate trap	Always repair, under warranty via the installer
5 to 10 years	Wear parts: ionisation electrode, seals, diverter valve, expansion vessel	Repareren; onderdelen € 20 tot € 300
10 to 15 years	Larger parts: pump, fan, gas valve, PCB	Repair up to 40 per cent of the new price; replace if it is the heat exchanger or a second major repair
15 years and older	Onderdelen worden schaars (fabrikanten leveren tot 10 jaar na einde productie), rendement daalt	Small repairs only; plan replacement

The 40 per cent rule with real prices

A new combi boiler typically costs € 1,800 to € 2,450 installed (all prices); 40 per cent of that is € 720 to € 980. Set the repair against that: the part plus € 90 to € 150 labour per call-out.

Repair	Part	Total incl. labour	Boiler less than 12 years old	Boiler more than 12 years old
Sensor, air vent, condensate trap, ionisation electrode	€ 10 to € 60	€100 to €200	Repair	Repair
Expansion vessel, diverter valve, water pressure sensor	€ 60 to € 200	€ 150 to € 350	Repair	Repair, unless it is the second repair in a year
Circulation pump, gas valve	€ 150 to € 350	€ 250 to € 500	Repair	Weigh it up; replace at 15 years
Fan, PCB	€ 250 to € 500 (fan prices)	€ 350 to € 650	Repair	Replace
Heat exchanger	€ 500 to € 900 (details)	€ 700 to € 1,200	Only under heat exchanger warranty	Replace

The rule is a rule of thumb, not a law. Two exceptions upwards: a boiler with a 10-year heat exchanger warranty where the heat exchanger itself fails (then you only pay for labour), and a boiler that fits well with a planned hybrid heat pump. Two downwards: a boiler that needed an engineer twice in one winter, and a boiler whose PCB is no longer available new.

Factor in efficiency

A condensing boiler from 2010 achieves 90 to 93 per cent efficiency in practice; a new one with good controls 96 to 98, mainly thanks to better modulation and lower flow temperatures. At 1,200 m³ of gas a year, that saves 80 to 120 m³; what that is worth depends on your energy prices. Add the avoided risk of a second repair, and a new boiler earns back the difference compared with an expensive repair in three to five years. That argument does not apply to small repairs: you will never earn back € 150 for a sensor through efficiency.

Signs that the end is near

• Fault codes keep coming back, especially relating to pressure, temperature and ignition; see the code database.
• Topping up more than twice a year: an internal leak in the heat exchanger or a tired expansion vessel, see water pressure dropping.
• Gas consumption rises without explanation: a dirty heat exchanger or poor combustion.
• Rusty water from the condensate trap or brown deposits around the heat exchanger.
• The engineer reports that parts are "end of life" or only available as reconditioned.
• The boiler is 15 years old and a renovation, move or heat pump is planned; then it is the moment to combine.

Servicing that buys lifespan

Annual servicing by a qualified professional is a condition of the warranty and the cheapest way to extend a boiler's life. In addition: a magnetic filter on the return, keeping the water pressure stable without constantly topping up, bleeding radiators at the start of the heating season, not setting the flow temperature higher than necessary (lower temperatures mean less wear and less gas), and a modulating thermostat instead of on/off, see which thermostat fits.

Replacing it anyway? The choices

Start with the CW class and the output (choosing a CW class), then choose the brand (brands compared) and decide what else is needed (flue, dirt separator, expansion vessel). Boilers with a reputation for a long life and readily available parts: Intergas Kombi Kompakt HRE 36/30 (€ 1.099), Remeha Tzerra Ace-Matic 35c (€ 1,049, tops itself up) and Nefit ProLine NxT HRC 30 (€ 1,190). All models in the · ; Instalpunt does not install, so have a qualified local installer fit it, see the installation service. The complete step-by-step plan is in Which boiler suits my home?.

Frequently asked questions

When should you replace a boiler?

When the boiler is 15 years or older and needs a major repair (heat exchanger, PCB or fan), when it needed an engineer twice in one winter, or when parts are no longer available new. Recurring fault codes, constant topping up and rising gas consumption without explanation are also signs that replacing is wiser than repairing.

How long does a boiler last?

15 years on average; with annual servicing and the right output, 18 to 20 years. After 15 years, parts become scarce and efficiency drops.

Is a € 400 repair on a 14-year-old boiler sensible?

Usually not. The chance of another repair within two years is high, the efficiency is 10 per cent lower than new, and a new boiler typically costs from € 1,800 installed.

Can I keep an old boiler and add a hybrid heat pump next to it?

Only if the boiler is less than about 8 to 10 years old. With an older boiler, choose a boiler plus heat pump package; otherwise you will still be replacing it within a few years and the controls will have to be redone.

Hoe weet ik hoe oud mijn ketel is?

From the serial number on the rating plate; with Intergas it starts with the year of manufacture, and for other brands we will read it for you. See How to read the rating plate.