Six reasons not to buy a heat pump

Heat pumps are currently the frontrunner to replace gas boilers over the coming decades as the country moves towards net zero.

The Government wants 600,000 of the devices installed each year by 2028, while gas boilers will be phased out. By 2035, some households will be banned from replacing gas boilers like-for-like, although that will not mean having a pre-existing gas boiler will suddenly become illegal.

In September, Rishi Sunak announced several changes to the Government’s net zero plans, which include gas boiler ban exemptions for the fifth of homes for whom heat pumps would be ineffective. This includes off-gas-grid-homes, people who need expensive retrofitting or a very large electricity connection.

The Government has also increased heat pump grants to £7,500, up from £5,000 for air source heat pumps and £6,000 for ground source options. However, the typical cost of buying and installing a heat pump is £13,000.

Publicly available figures from standards body MCS suggests there are now more than 203,400 heat pumps installed across the whole of the UK, as uptake improves but still falls drastically short of government targets.

Heat pumps don’t suit all homes; here are six reasons why it might not be the best option for you.

1. The cost is prohibitive

The main barrier to installing these devices for most homes is the disproportionately large upfront cost when compared to traditional heating systems.

A survey for the RSK Group, the services provider, found that on average the public believes heat pumps cost around £3,290 to purchase and install.

In reality, the costs are much higher. While a replacement gas boiler can cost around £1,000 to £3,000, an air source heat pump can cost between £7,000 and £14,000 to purchase and install, and ground source heat pumps can cost between £15,000 and £35,000.

The Government expects the cost of these devices to come down in the coming years and earlier in 2023 a price war among energy providers has seen a number of low-cost models enter the market, as energy companies compete to drive prices down.

In January, British Gas announced it would fit heat pumps for as little as £2,999. Weeks later, Octopus Energy, a rival, announced it would be launching a heat pump at £2,500 – the same price or cheaper than a typical gas boiler. However, most consumers are expected to end up paying between £3,000 and £3,500, depending on the size of their home.

2. They are slower at heating homes

At present, heat pumps can be slower at heating a home than a conventional boiler or electric heater. Traditional central heating systems heat water by burning gas, which can take radiators to around 75C. 

Hydrogen boilers will operate in a similar manner once they become widely available.

Heat pumps only heat water to a maximum of around 65C, meaning houses that use them take longer to warm up.

3. Better models will be available in the near future

In 2022, the UK installed 42,779 heat pumps, which equates to 1.48 per 1,000 people and was the smallest number in Europe. The figure was also well short of the Government’s 600,000 target, and a tiny amount in comparison to the 1.6 million gas boilers installed over the same period. 

In an interview with The Telegraph, former Business and Energy Secretary Kwasi Kwarteng conceded that, while gas boilers had been “refined over many years … heat pumps are still in their infancy”.

As the number of heat pumps installed every year will accelerate in the coming years, it is likely that the price of the devices will come down significantly.

As new models are developed, more efficient devices are also likely to become commercially available, in addition to the cheaper ones announced by British Gas and Octopus.

This means that households committing to a heat pump now may be at risk of jumping the gun, and may miss out on a cheaper and more efficient and effective device in several years’ time.

4. They might not work in your home

Almost all houses can accommodate an air source heat pump, but a ground source device requires more land.

Not all flats will be compatible with air source heat pumps however, as the devices usually need to sit on the ground outside to work. This can be an issue for those living in terraced houses, where outside space may be limited.

Small flats may also lack the indoor space required for the devices, as large hot water cylinders are required. 

In some cases, they can be mounted on a wall, but need to be somewhere accessible so that settings can be adjusted.

Air source heat pumps also generate some noise when working, especially in cold weather. 

David Holmes of Boiler Guide said: “The important point to take away is that for the right property, an air source heat pump can be an effective low-carbon heating system. 

“However, with so many ‘ifs’ and ‘buts’ around the technology, there is no blanket solution to how we will heat homes in the future.”

5. They don’t cut bills by very much

The potential savings gained by installing a heat pump depends on what type of system it is replacing. 

Whether a heat pump will slash a household’s bills depends on the heating system they are replacing. According to the Energy Saving Trust, a charity, a standard air source heat pump in an average-sized, three-bedroom semi-detached home can shave hundreds off a household’s annual fuel bill.

Such a household swapping out an old G-rated gas boiler would save £590 a year on energy. Replacing a newer A-rated boiler would only save £115 a year. Homes using LPG or electric heaters would also save money each year, the charity calculated. But homes reliant on oil boilers may actually lose money if they opt for a heat pump. The charity said a new A-rated oil boiler was £135 a year cheaper to run than a heat pump.

This is likely to change over the next decade. The Government plans to move green energy surcharges, which are currently applied to household electricity bills, onto gas bills. 

Ministers are expected to phase in the changes over a period of up to 10 years, however, so for the foreseeable future gas will remain cheaper. 

Air source heat pumps can become less efficient when the temperature outside is colder. According to Green Age, an energy-saving advice service, the coefficient of performance of an air source heat pump in the winter can be less than two, down from a typical three. 

This means the heat pump generates one unit of heat for every unit of electricity required to power the device.

Gas boilers have a lower coefficient of performance than this, at 0.85, but as gas is far cheaper than electricity, costs are roughly similar. 

6. They don’t work well in poorly insulated homes

When considering heat pumps, many households will have to also factor in the cost of properly insulating their home. 

Homes need to be well insulated for heat pumps to be effective because the devices work at lower temperatures and so will struggle to get the house warm and keep it to temperature. They work better with lower-temperature heating systems, such as underfloor heating.

Households may also need to upgrade their radiators to match their preferred heat pump and would need to spend up to £2,900 for a typical five-bedroom house. However, this cost does not cover the expense of labour required to install a new heating system.

Radiators aside, when deciding to install a heat pump, many households need to consider the cost of improving the insulation of their home as well.

Effective insulation is crucial for heat pumps to function optimally because these devices operate at lower temperatures, and therefore, may struggle to heat the house adequately and maintain the desired temperature. Heat pumps perform better with heating systems that use lower temperatures, such as underfloor heating.

It is estimated that approximately 25 million homes in Britain do not have sufficient insulation. Upgrading a poorly-insulated home can be expensive, potentially costing thousands of pounds, but ultimately, it pays for itself through reduced energy bills.

The level of insulation required for a house depends on its age, with older homes typically requiring more extensive insulation measures, which can be considerably more expensive.

Houses built after the 1920s usually have cavity walls, which can be insulated for around £1,000, resulting in significant energy savings. According to the Energy Saving Trust, a semi-detached home can save around £395 annually by insulating cavity walls.

Solid walls, which are more common in older homes, are costlier to insulate, with external insulation costing approximately £12,000 and internal insulation costing around £8,500, excluding redecorating expenses. Floor insulation for a typical “suspended” floor can cost between £1,600 and £2,900.

Regardless of a house’s age, loft insulation is the cheapest and most recommended option. Insulating the roof of an average semi-detached house can cost around £640, resulting in energy savings of approximately £355 per year.

This article is kept updated with the latest advice.