Heat pump vs boiler comparison

Heat pump vs boiler round 1 – Efficiency

The efficiency of a home heating system is essentially how much of the energy supply is converted into useful heat energy. Historically, old boilers are considered 50 – 75% efficient, which means that a half to a quarter of the energy supplied to the boiler was wasted. Modern high-efficiency boilers (gas, LPG and oil) and biomass boilers have a much-improved efficiency of around and above 90%, with only small amounts of heat lost through the flue.

On the other hand, the efficiency of heat pumps can, in effect, reach as high as 350% (or in technical terms, a Coefficient of Performance of 3.5). This is because heat pumps work by absorbing the heat occurring naturally outside of your home and moving it indoors.

Heat pump vs boiler: 1 – 0

Heat pump vs boiler round 2 – Lifespan

A typical air source heat pump lasts for around 15 years, but allegedly newer models and ground source heat pumps have a lifespan of around 25 years. This longevity is put down to their robust design, and with only a few moving parts, there’s very little that can actually go wrong.

In comparison, a typical gas or LPG boiler’s lifespan is around 8 – 12 years.

Heat pump vs boiler: 2 – 0

Round 3 – Heat Pump & Boiler Space

The outdoor fan unit of an air source heat pump usually takes up as much space as a washing machine. This is usually (but not always) connected to an indoor heat exchanger (or hydrobox), which is roughly the same size as a regular boiler. Finally, the hydrobox connects to a hot water cylinder, just like a regular gas boiler.

A ground source heat pump requires roughly twice the floor area of your home (including all floors) to be split and dug into trenches, where long pipes are laid. This is obviously a large plot of land (and not a quick installation), but once these pipes are buried underground, it’ll be unnoticeable once the flora has regrown or concrete re-laid. The actual ground source heat pump unit sits inside your home, and can be anywhere between the size of a regular boiler down to that of a large shoebox.

On the other hand, some modern boilers (or ‘combi’ boilers) take away the need for a hot water cylinder altogether, heating water straight from the water mains. Generally speaking, these are only suitable in small houses or flats though.

So if you’re including the outdoor space required, the ground source heat pump is the biggest loser for this round. However, if you’re only comparing which heating system takes up the most room inside your home, the biomass boiler would probably be the biggest. These pellet-burning green heating systems are larger than standard gas boilers, although this will depend on the size of your house and the demand for heat.

Heat pump vs boiler: 2 – 0

Heat pump vs boiler round 4 – Upfront cost

If you’re looking for the quickest and cheapest option, you’re better off sticking with a gas boiler. The Energy Saving Trust (EST) estimates that a standard gas boiler replacement will set you back on average £2,300.

For homeowners not on gas mains, the cost of an air source or ground source heat pump by comparison is between £6000 – £8000 (air source, EST) or £10,000 – £18,000 (ground source, EST). However, you will be able to claim the vast majority of this back from the Renewable Heat Incentive (subject to performance). Similarly, you can receive a tax-free RHI income with a biomass boiler, which is predicted to cost £8,000 – £15,000 (EST).

Considering a heat pump’s longevity, it’s worth noting that you may also need to replace your boiler twice in the space of one heat pump’s lifetime.

Heat pump vs boiler: 2 – 1

Round 5 – Heating running costs

Despite the cost of electricity being roughly 4 times more than gas, oil and LPG*, the running costs are surprisingly similar (this is down to the heat pump’s high efficiency). What this means is, in the event of electricity coming down in price in the future, the running cost of heat pumps would be a fraction of conventional heating methods. Given the volatile nature of changing energy prices, we think this is likely to happen.

Of course, this is speculative – we can’t know for certain if and when these prices might change, but as more and more solar farms, wind farms and hydroelectricity plants appear across the UK, it stands to reason that the cost of electricity will fall.

Heat pump vs boiler: 2 – 2

Heat pump vs boiler round 6 – Maintenance

While annual maintenance checks are advised for heat pumps, they’re not necessary. They can help to preserve a high efficiency and prolong life expectancy, but you can get away with not having routine checks without serious consequences.

On the other hand, it’s strongly advised that boilers have at least annual maintenance checks from HVAC professionals. This is to ensure safety, namely to reduce the risk of carbon monoxide poisoning.

Heat pump vs boiler: 3 – 2

Round 7 – User experience

Since both gas boilers and heat pumps are fully automated, the user experience will largely depend on the model you choose. As with most modern appliances, there are umpteen extra functions to improve ease of use, comfort and control. App-controlled systems, timers and programmable room thermostats are just a few of the functions we think are worth looking out for.

Unfortunately, a biomass boiler will require slightly more effort, as you’ll have to manually fill it with wood pellets each time. There are options to have pellets delivered to your door, but this will depend on a willing third party located in your area.

Heat pump vs boiler: 3 – 2

Round 8 – Extra costs

While most boilers shouldn’t take more than a couple of days to replace, there are always extra costs that you hadn’t accounted for. The reality is that a heat pump has a few of its own requirements to meet so that it can work effectively. The building must be reasonably well insulated to achieve a low flow temperature, and you may have to increase the size of your radiators. If this is the case, we suggest installing underfloor heating.

Although costly, the large surface area of underfloor heating makes for a significantly lower flow temperature (thus smaller electricity bills), and it also means a room is much quicker to warm up than if you only had radiators.

Heat pump vs boiler: 3 – 3

Round 9 – Eco friendliness

Despite the efficiency of gas, oil and LPG boilers rising to approximately 90%, heat pumps don’t burn fossil fuels to generate heat, making them the clear winners of this round. Their high efficiency also means that even if the electricity powering the heat pump was generated in a coal-fired power station, the carbon emissions given off would be minimal.

Furthermore, there’s the option to power heat pumps on green electricity (from solar farms or wind farms), which would practically reduce their carbon emissions to zero.

Biomass boilers are also a green heating option worth considering. As they burn wood, they’re only emitting the same amount of carbon emissions that were absorbed, so they’re technically carbon-neutral.

Heat pump vs boiler: 4 – 3

Heat pump vs boiler highlights

So, after a gruelling 9 rounds pitting the heat pump against the boiler, do we have a out-and-out winner? Not really.

For homeowners who are off the gas mains grid, building a sustainable home, or simply trying to be a bit more environmentally friendly, we’d suggest investing in a heat pump. For those on gas mains, it’s probably better financially to replace your boiler with a high-efficiency one.

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