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Heat Pumps

Research, scores and rankings for 16 ground source and air source heat pump brands.

We look at types of heat pump, their efficiency and performance, environmental impact, carbon savings, running costs, and grants. Plus give our Best Buys and recommended buys.

About Ethical Consumer

This is a product guide from Ethical Consumer, the UK's leading alternative consumer organisation. Since 1989 we've been researching and recording the social and environmental records of companies, and making the results available to you in a simple format.

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What to buy

What to look for when buying a heat pump:

  • Does it have good efficiency ratings? This will be listed as A+++ and also sometimes as SCOP or SFP. The better the efficiency, the more energy you will save and the more you will help the climate.

Subscribe to see which companies we recommend as Best Buys and why 

What not to buy

What to avoid when buying a heat pump:

  • Does the company have no conflict mineral policy? The big electronics companies have a significant influence on what goes on in the DRC.

  • Does it have a good supply chain policy? Many of these companies will be manufacturing in the far east where workers’ rights may be less well protected.

Subscribe to see which companies to avoid and why

Score table

Updated live from our research database

← Swipe left / right to view table contents →
Brand Score(out of 20) Ratings Categories Positive Scores

Kensa heat pumps

Company Profile: Kensa Group Ltd

Danfoss DHP-H Heat Pump

Company Profile: Danfoss Heat Pumps UK Ltd

Glow-worm Clearly heat pumps

Company Profile: Vaillant Group UK Limited

Vaillant heat pumps

Company Profile: Vaillant Group UK Limited

CTC heat pumps

Company Profile: CTC

LG heat pumps

Company Profile: LG Electronics Inc

Nibe heat pumps

Company Profile: NIBE Energy Systems Limited

Daikin heat pumps

Company Profile: Daikin Industries Ltd

Grant heat pumps

Company Profile: Grant Engineering (UK) Ltd

Viessmann heat pumps

Company Profile: Viessmann Limited

Dimplex heat pumps

Company Profile: Glen Dimplex Group

Worcester heat pumps

Company Profile: Worcester Heat Systems

Mitsubishi Electric Ecodan heat pumps

Company Profile: Mitsubishi Electric Corporation

Panasonic heat pumps

Company Profile: Panasonic Corporation

Samsung heat pumps

Company Profile: Samsung Electronics Co Ltd

What is most important to you?

Product sustainability

Our Analysis

Heat pumps do not look like a hugely sexy technology, but what they do is pretty magical. Technologically, they are just fridges in reverse. They move outside heat – either from the air or from the ground – into your house.

The way they work makes them hugely efficient, which is why they are being viewed by so many as the key to decarbonising the UK’s heating.

Heat pumps are still rare in the UK, only about 30,000 were installed last year compared to about 1.5 million gas boilers. But internationally they are widely used. In Sweden and Switzerland they account for about a third of heating system sales.

The UK government has just announced that it intends to try to reach 600,000 heat pump sales per year by 2028, a twenty-fold increase.  It hopes that there will be 5.5 million heat pumps installed in homes by 2030, of which 2.2 million will have been installed in new homes, and the rest retrofits.

Heat pump performance

Heat pumps have had a mixed reception in the UK.

Trials conducted between 2008 and 2013 initially showed that they were performing very poorly, much less efficiently than in other European countries. But in the second phase of the trial, once specification and installation were improved, they improved markedly.

Efficiency seems to have been improving further since, and there are more trials ongoing now.

Where they are specified and installed well, satisfaction levels seem to be high – around 80% of people say that they are happy with their pump.


Cost and running costs of heat pumps

For many people heat pumps probably don’t fall into the ‘win-win, save money and save the climate’ bracket. We cover cost in more detail below, and also see our feature on heating and energy grants.

However, there are UK properties for which they are much more financially attractive, particularly the 14% which are not connected to the gas grid. And if you’ve already insulated your house, getting one is a major step you can take to help the climate.

The biggest problem with heat pumps is the cost. The upfront costs are quite high, and if you’re comparing one against a modern efficient gas boiler, you sadly may not save money on running costs.

Electricity is currently about 3 or 4 times the cost of gas. So although heat pumps are about 3 or 4 times more efficient, these cancel out and you could expect your running costs to be about the same.

  • The Climate Change Committee estimates the average cost of an air-towater heat pump + installation at £6,415, and ground source at £13,380, with up to £3,500 additionally required to make house changes such as increasing radiator size. Installation prices can, however, vary a lot. The Energy Saving Trust estimates an efficient gas boiler replacement to be about £2,300.
  • A hybrid system can be cheaper if you already have a boiler and are just installing a heat pump to work alongside it, because you may get away with a lower capacity heat pump and without replacing your radiators. Costs vary, but one report suggested that it could be around 30% less than a full heat pump system.
  • There’s less information available about air-to-air heat pumps. On their face they look significantly cheaper, but you would need something else for hot water, and additionally you may need more than one. Those factors may well counteract the savings.

The Climate Change Committee estimates that the price of the pump and installation may fall by about 23% over the next fifteen years, if – as it recommends – the UK becomes such a large heat pump market that there start to be efficiencies of scale involved.

Government Grants for heat pumps

There are, luckily, government schemes to help with the cost, and these can make heat pumps much more financially attractive. The two main ones at the time of writing (February 2021) were the renewable heat incentive (RHI) and the Green Homes Grant (latter is now closed to new applicants but has been replaced). These can cover a significant proportion of the cost (up to £5,000 or £10,000 if you are on a low income). You may also qualify for a 5% VAT reduction if you are over 60 or on benefits.

Ground source, air-to-water and hybrid heat pumps are eligible for these schemes.

Air-to-air are excluded, probably because of the difficulty of differentiating them from straight air conditioners. But they aren’t the only type of heat pump that can be used for cooling too – many heat pumps can be switched to cooling mode.

Different types of heat pump and what do you need to install a heat pump

Installing a heat pump is likely to require other changes to your house. Firstly, they do produce less heat, so the house needs to be well insulated.

Secondly, most heat pumps are at their most efficient when they heat radiator water to 35-45 degrees, as opposed to the 65-80 degrees normal with gas boilers.

This means that you may need larger surfaces like large radiators or underfloor heating, and to increase the size of your hot water tank.

There are some ‘high temperature heat pumps’, which are optimised to heat to a higher temperature so they can be used with standard-sized radiators. But they are less efficient, the external units are much larger, and the pumps are 20-35% more expensive than standard ones.

Installation involves drilling holes through the walls, which may require planning permission.

Type 1 air source heat pumps: air to water

Most of the heat pumps installed in the UK are air to water. They do both space and water heating.

They can be installed on almost all properties, including flats. A normal pump is about the size of a fridge, and you just need a place outside where it can be fitted to a wall or placed on the ground, with space around it to get a good flow of air.

All air source heat pumps do produce some noise, as they contain a fan, but the modern ones are much quieter – about 40 to 60 decibels, which is rarely a problem.

Type 2 air source heat pumps: air to air

Air to air heat pumps are just air conditioners that have been put into reverse. They blow hot air into your house, so they only do space heating. You will need something else for hot water.

However, air to air pumps do have some advantages. The pumps are cheaper and have good efficiency. Since they don’t use radiators, you won’t need to install bigger ones, although you may need ducting (pipes) in order to carry the hot air around to different rooms.

Ground source heat pumps

Ground source heat pumps (see graphic right) take heat from the ground instead of the air, using pipes buried outside the house. This makes them much more efficient, and silent, but they are more expensive and only suitable for a limited number of properties due to the outside space requirements.

In the case of the horizontal ones, pipes are buried in your garden in a long trench about a metre deep – you will need an area about twice the size of your house.

The vertical ones have the pipes in a series of boreholes instead, so they require much less space. But they are more expensive to install and you will still need space for the drilling machinery – they go down around 70 to 100 metres.

Hybrid heat pumps

Hybrid systems combine a heat pump and a traditional boiler. The theory is that the heat pump does most of the work, but the boiler helps out in particularly cold weather, when heat pumps struggle.

Hybrids have some advantages, and many complete decarbonisation scenarios incorporate some as a way of reducing peak electricity demand.

Nibe Electricity is quite difficult and expensive to store in large amounts, so huge peaks – like on very cold winter evenings, when everyone turns their heating up to max – are a problem.

The Climate Change Committee’s 2019 total decarbonisation scenario has a quarter of the homes that run on heat pumps in 2050 using a hybrid system, with the boiler part using hydrogen, or bioenergy in the case of homes off the gas grid.

Gas fired and water-source heat pumps

You can get gas-fired heat pumps. They do use less gas than boilers, but most people seem to be suggesting that they aren’t hugely cheaper than the electric ones, so there doesn’t seem to be any compelling reason to get one when it is better to get off gas altogether.

You also get water-source heat pumps, but they are rarely used at domestic level.


You should make sure that your installer is accredited by a Microgeneration Certification Scheme (MCS)-appointed certification body. It is a good sign if they are also registered with other organisations and bodies, such as the Renewable Energy Assurance Ltd (REAL) and the Ground Source Heat Pump Association, which encourage high installation standards.


Heat pump efficiency and environmental impact

The main measure of a heat pump’s efficiency is called the coefficient of performance (COP). It measures how many units of heat you get out per unit of energy you put in.

A 100% efficient direct electric heater, which does no heat pump magic, has a COP of one. A 90% efficient gas boiler has a COP of 0.9.

Standard ground source heat pumps average COPs of around four, and air source about three.

However, the COP varies depending on the weather. So, when you’re comparing individual pumps you want to look at the average COPs they manage over a heating season. This is either given as the Seasonal Coefficient of Performance (SCOP) or the Seasonal Performance Factor (SPF).

Carbon footprint savings from heat pumps

As the grid decarbonises over your heat pump’s lifetime, emissions will fall towards zero. But even now, the annual carbon savings are good.

The current carbon footprint of a unit of UK electricity is on average about 1.3 times that of natural gas. You can do a rough estimate of the emissions savings you can get from heat pumps from this and their SCOP – if it is three, emissions would be less than half of those from the most efficient gas boiler.

Estimates of immediate emission cuts from studies are around 70% for standard heat pumps, 50-60% for high temperature heat pumps, between 18 and 55% for hybrid systems (it depends on the set up and how you use them), and about 20% for gas-fired heat pumps.

To put it in absolute figures, the Energy Savings Trust estimates that air source heat pumps save more than two tonnes of CO 2e per year on the most efficient gas boilers, right now. The average UK carbon footprint per person, including all imported goods, is about twelve.

Energy labels for heat pumps

All heat pumps have energy labels. Although they may be changing now we have left the EU, the familiar ErP label is still being used.

The same scale is used for all heating technologies, meaning that heat pumps by definition fall into the top three classes: A+, A++ or A+++. The rating is based on the SCOP.

When heat pumps are required to deliver a hotter output their efficiency drops. Heat pumps have two ratings for space heating, for low temperature delivery at 35°C, and medium temperature delivery at 55°C.

There are several other numbers on the label as well, including a decibel noise rating, and a hot water rating if they produce hot water, although heat pumps are normally all in Class A for that. To achieve higher efficiency, they need to be combined with solar heating.

The quantity of hot water will also be illustrated by a tap symbol indicating sizes (tap profiles) from 3XS to XXL.

Refrigerants in heat pumps

Heat pumps use refrigerants, and the most common traditionally has been a hydrofluorocarbon (HFC) called R410A, which has a Global Warming Potential (GWP) of 2088, meaning that it has 2088 times the warming effect of CO2.

Although it should be possible to recover the refrigerant at the end of life, there may be some leakage.

R410A is now being phased out under EU F-Gas regulation. Some heat pump manufacturers, such as Mitsubishi, are moving to another HFC called R32, which has a GWP of 675, although that too is going to start being phased out soon.

Others such as Vaillant are switching to propane, which has a GWP of 3, or to ammonia or CO2.

But some of these have their own problems, such as being unacceptably toxic or significantly less efficient, meaning that more electricity is used. And while the grid is still half based on fossil fuels, this can result in a higher carbon footprint than the ones with high GWPs (although once the grid is fully decarbonised, we won’t need to worry about that).

According to the Climate Change Committee: “if existing standards are maintained, the greenhouse gas savings of a switch to heat pumps are orders of magnitude higher than the additional F-gas [HFC] emissions.”

Given the complexity and that the climate impact is small, we decided not to rate companies on the basis of the refrigerants they use in their heat pumps.

Is my home heat pump ready?

Matt Franklin of Carbon Coop raises a few considerations for designing an efficient system.

With a new grant for heat pumps – the Boiler Upgrade Scheme, launching in April 2022 in England and Wales – many people are asking whether they need to make significant investments in insulation to make their homes ‘heat pump ready’. Whilst some say your home needs to meet PassivHaus standards, others say you can just go ahead.

So what does ‘heat pump ready’ actually mean?

The reality is that without taking a look at your house as a system, a new heat pump won’t work efficiently. If you don’t make any changes you are likely to end up with a heat pump which is either oversized, too expensive, or not adequate to heat your home.

Getting an overly large heat pump might seem like a good way to avoid extra work, but it will cost more and take up more space.

With installations costing several thousand pounds, making general improvements to your home first can make a significant difference to the price of the pump and the running costs over its lifetime.

With an oversized heat pump and no other changes, you may still cut your carbon emissions (by eliminating gas) and have an efficiency broadly comparable to a gas boiler, but, to see lower bills, a more comfortable home and a radically reduced carbon footprint you need to do more.

Improving your home’s insulation, draught proofing, replacing some radiators, etc, means that you will be able to install a heat pump which is smaller both in size and in terms of energy consumption, quieter and overall simpler to run.

Using a rough demonstration generated from People Powered Retrofit’s home assessment tool, it's possible to see the potential of a low, medium and high impact retrofit, and the size of heat pump that could then be used i.e. small, medium and large.

  • Baseline scenario: Peak heat load = 11.1kW (large heat pump required)
  • Scenario 1 low impact retrofit: Peak heat load = 8.8kW (medium heat pump)
  • Scenario 2 medium impact retrofit: Peak heat load = 5.1kW (small heat pump)
  • Scenario 3 high impact retrofit: Peak heat load = 3.8kW (small heat pump)

Any kind of retrofit reduces the size of the heat pump required – but deep retrofit has a significant impact. So, whilst you don’t have to go for a deep retrofit before you install a heat pump, the more you can do the better.

Manufacturers of Heat Pumps

We found ethical issues around both carbon reporting and tax avoidance. 

Despite manufacturing this emissions reduction technology, only a handful of companies scored well in our ranking of carbon management and reporting for their own operations. Our criteria require, amongst other things, reporting annually on emissions and setting targets for reductions in line with international agreements. This ranking appears in the Climate Change column. The worst were Bosch (Worcester), Glen Dimplex, Grant Engineering (Grant), Viessmann

Most companies in this guide received our worst rating for likely use of tax avoidance strategies. The exceptions were Kensa, Danfoss, Vaillant (including Glow-worm), and Grant Engineering (Grant), which all received a best, and Mitsubishi Electric, which received a middle rating. Kensa and Mitsubishi’s scores were however brought down by other parts of their company structures.

Which company makes what kind of heat pump?

Type of heat pump Brand
Ground source Worcester Greenstore, Kensa, CTC, Daikin, Nibe, Vaillant, Samsung, Viessman, Dimplex, Danfoss
Air to water Worcester Greenstore, CTC, Daikin, Vaillant, Dimplex, Panasonic, Glow-worm, LG, Mitsubishi, Viessmann, Samsung, Nibe, Danfoss, Grant
Air to air Worcester Greenstore, Daikin, Panasonic
Hybrid Worcester Greenstar, Vaillant, Daikin, Glow-worm, Viessmann, Panasonic, Mitsubishi, Samsung, Grant
High temperature Daikin, Dimplex, Panasonic, LG, Mitsubishi, Viessmann, Nibe


Company behind the brand

Kensa scores well across our ratings, receiving our best rating for carbon management and reporting, environmental reporting and supply chain management.

It is the first and only dedicated ground source heat pump manufacturer in the UK. Its factory in Cornwall is heated using its own heat pumps, is based on a former mine site, and uses water in a disused mine shaft as the heat source for the pumps.

The company has created the first ground source heat pump small and quiet enough to be installed in flats and apartments, and was the first to install ‘shared ground loop array systems’ – a form of shared heating network whereby multiple households or buildings can share low-carbon heating infrastructure, allowing impacts to be scaled throughout communities. Kensa is 36% owned by Legal & General Group.

Want to know more?

If you want to find out detailed information about a company and more about its ethical rating, then click on a brand name in the Score table. 

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