An air source heat pump typically lasts 15 to 20 years, with the outdoor unit often requiring replacement after around 15 years. The UK Energy Saving Trust states that a well-maintained system can operate efficiently for 20 years or more, while the indoor components such as the hot water cylinder may last 10 to 15 years before needing attention.
Key factors that affect lifespan include:
- Installation quality: Poor installation can reduce lifespan by 5-10 years. MCS certification is a reliable indicator of a competent installer.
- Annual servicing: Skipping annual checks can lead to compressor failure, costing £1,500-£2,500 to replace (roughly the price of a new boiler).
- Usage patterns: Running the pump constantly at low temperatures (e.g., 35°C flow) is less stressful than cycling on and off at higher temperatures.
- Location: Units exposed to coastal salt or industrial pollution may corrode faster, reducing lifespan to 10-12 years.
| Component | Typical lifespan | Replacement cost (installed) |
|---|---|---|
| Outdoor unit | 15-20 years | £7,000-£11,000 |
| Indoor hot water cylinder | 10-15 years | £800-£1,500 |
| Compressor | 10-15 years | £1,500-£2,500 |
This matters more if you are planning to stay in your home for 15+ years, as you will likely need to budget for a replacement unit within that timeframe. It matters less if you are a short-term owner (under 5 years) or are installing a heat pump as a secondary heating system, where wear is lower.
Bottom line: A properly installed and serviced air source heat pump should last 15-20 years, with the outdoor unit being the main component to replace. Budget for an annual service at £150-£250 and plan for a full replacement after 15 years.
Sources
A worked example
A 1930s semi-detached house in Manchester with a 12 kW air source heat pump installation costs £6,500 after the £7,500 Boiler Upgrade Scheme grant and 0% VAT until March 2027. The homeowner replaces an old gas boiler and saves £395 per year on heating bills according to the Energy Saving Trust. With annual servicing at £200, the net yearly saving is £195. The payback period on the upfront cost reaches 33 years, which exceeds the typical 15 to 20 year lifespan of the outdoor unit. Over a 25-year lifetime the system generates £4,875 in net savings after servicing costs, though the homeowner should budget £7,000 to £11,000 for a replacement outdoor unit around year 15.
| Item | Figure |
|---|---|
| Upfront cost after grants | £6,500 |
| Yearly savings | £195 |
| Payback period | 33 years |
| 25-year lifetime savings | £4,875 |
What homeowners often get wrong
The most common mistake is assuming an air source heat pump works like a boiler and needs to cycle on and off. Here are three misconceptions that shorten lifespan and inflate costs.
- Running the pump intermittently saves energy Heat pumps are most efficient when running constantly at low flow temperatures around 35°C. Cycling on and off forces the compressor to work harder every restart, which can reduce lifespan by up to 5 years and increase electricity bills by £150 per year.
- Any installer can fit a heat pump properly Using a non-MCS certified installer voids the BUS grant, the 0% VAT relief, and the manufacturer warranty. Poor installation causes early compressor failure at £1,500 to £2,500, and the system may lose 10 years of its expected lifespan.
- Skipping annual servicing saves money A missed service lets refrigerant leaks and dirty filters go unnoticed. The resulting compressor failure costs £1,500 to £2,500 to fix, which is roughly the price of a new gas boiler and more than 10 years of servicing fees at £200 each.
Quick reference
- An air source heat pump outdoor unit lasts 15 to 20 years with proper maintenance according to the Energy Saving Trust.
- The indoor hot water cylinder typically needs replacement after 10 to 15 years, which costs £800 to £1,200.
- Annual servicing costs £150 to £250 and is required to maintain the manufacturer warranty and BUS grant conditions.
- Running the pump at 35°C flow temperature instead of 50°C can extend compressor life by 3 to 5 years.
- Coastal or industrial pollution can corrode the outdoor unit and reduce its lifespan to 10 to 12 years without protective measures.
Frequently Asked Questions
In the UK, an air source heat pump typically lasts 15 to 20 years, with the outdoor unit often needing replacement after around 15 years. The Energy Saving Trust states that with proper annual servicing, a system can operate efficiently for 20 years or more.
Replacing the outdoor unit of an air source heat pump in the UK costs between £7,000 and £11,000 installed. The indoor hot water cylinder replacement costs £800 to £1,500, while a compressor replacement can set you back £1,500 to £2,500.
Yes, annual servicing is essential for air source heat pumps in the UK, costing around £150 to £250 per year. Skipping these checks can lead to compressor failure, which costs £1,500 to £2,500 to replace.
Key factors include installation quality (MCS certification is recommended), annual servicing, usage patterns (constant low-temperature operation is better), and location, units in coastal areas may corrode faster, reducing lifespan to 10-12 years.
Air source heat pumps are less beneficial for short-term owners (under 5 years), as you'll likely need to budget for a replacement unit within 15 years. They are more worthwhile if you plan to stay for 15+ years, given the typical lifespan of 15-20 years.
