Over the past few years heat pumps have become ever more popular as a home heating solution. But, despite the Boiler Upgrade Scheme incentive, they are still more expensive to install than gas boilers.
This means, when it comes to deciding if you want to choose an air source heat pump for your self build or renovation, most of us want to know just what its lifespan is in order to understand how long your investment will cover you for.
in this article, energy expert, David Hilton explains how to the potential life of a heat pump is calculated, so you can understand what might be the outcome when you choose one to heat your home.
How long do heat pumps last?
To determine how long a heat pump runs we use what is referred to as FLEQ hours. This stands for the 'Full Load Equivalent', which is the number of hours that the heat pump runs per year, based on its full load.
Breaking it down, this means if a heat pump was running at half capacity for 2 hours that would be deemed as 1 hour of FLEQ.
With a correctly sized heat pump installed in your home, the average number of FLEQ hours per year is 1800 hours for space heating, and then another 600 hours for hot water. If you run it within these parameters, and have regular annual services, then in general, you can expect the heat pump to last between 20 and 25 years.
Although there is a caveat to this. How long a heat pump lasts can also be influenced by the type of refrigerant compressor in your heat pump. Why? This is the hardest working component of a heat pump, and not all compressors are the same.
There are a number of different types of compressors, each with different qualities. The most common types of compressors used in heat pumps are either scroll compressors, rotary compressors or reciprocating compressors. Scroll compressors are often considered the better compressors for heat pumps as they have less moving parts and are often more efficient than the others. They are however more expensive.
A good compressor usually has a 10 year warranty, but, once again, there are some specific details that influence the effective life of a compressor.
The compressor is happy to run steadily, but what stresses and wears it is start-ups. So, even if you are within the FLEQ hours tolerance, if the compressor has many short start – stop cycles then the life expectancy of your heat pump will be less.
You can think of it a bit like a car. If you do many long distance journeys, then you will find that the car will potentially do more miles in its lifetime than a vehicle that is only used for frequent short trips.
Heat pump vs boiler life span
In the past, most of us will have had different types of boiler in our homes (mainly gas or oil), and when it needed replacing the calculations were a bit simpler. It was common knowledge that better quality boilers would cost a bit more, but last a bit longer, and we would find the happy medium between cost and quality to suit our home and budget.
That said, there are still differing anecdotes as to how long they last.
Some industry bodies claim that a condensing boiler will only last an average of seven years. Personally, I think you would be unlucky if that were the case. However, as with a heat pump, the life expectancy of a boiler is dependent on a number of things so the point at which you need to replace a boiler may differ.
If the boiler works a lot harder in a busy home, then it may not last as long as a boiler in a home with lower occupancy and / or lower heat loss, and better controls.
Marine environments are also detrimental to boilers as the sea air will be more corrosive to the heat exchanger. A good annual service is also critical to keep a boiler in optimal condition and prolong its useful life.
With all these things taken into account, I would say that a well maintained condensing boiler should last around 10 to 15 years depending on work load. Although there may be some differences depending on if it is an open vent (with gravity tanks in the loft) system, or unvented system. These different types of boilers are built differently and can also perform differently.
Improving the life span of a heat pump
As with a boiler, a heat pump also regular maintenance and servicing to optimise efficiency. It's also important that you operate them in the correct way.
Heat pumps like to run steadily. They prefer delivering heat ‘low and slow’ rather than ‘hot and fast’ like a boiler, but as a heat pump has more working parts than a boiler, and air source heat pump installation takes place outside the home, there are an additional few things that influence its useful life expectancy.
All external pipework, wiring and equipment needs to be protected from the elements, so it is important to make sure that any insulation is intact and that there are no leaks or corrosion.
Poor maintenance can lead to air or moisture getting into the system. Excess heat loss from the pipework, or the heat pump having to work far harder than it needs to, can also result in poor performance and excessive running costs. If the heat pump works hard, and is not maintained, then it may not last as long as expected.
When all things are considered, a heat pump should last longer than a boiler, and even though a heat pump costs more to install, as they become more mainstream the higher volumes will inevitably also bring more competition, and more competitive prices.
Of course, when it comes to replacing your heat pump, you also won't be installing it again from scratch which will make it a more comparable exercise to replacing a boiler with a like-for-like system.
Always start your heat pump journey by informing yourself with as much knowledge as you can about this type of heating system. Start with our easy 5 point checklist to see if your home is suitable for a heat pump, and make sure you understand the difference between low, medium and high temperature heat pumps to establish which one is best for your home.
