The 9 best air source heat pumps available in the UK today Written by Jane Hoskyn Reviewed by Roland Ellison Updated on 30 April 2024 Air source heat pumps are a clean, low-carbon way to heat your homeA heat pump could cut your home’s carbon footprint by up to 65%We spent 29 hours reviewing air source heat pumps on the UK marketCompared them across key criteria, including efficiency, warranty and weightFind the right heat pump for your home with our pick of the best Air source heat pumps extract heat from the air outside and compress it to deliver warm air and hot water for your home.By replacing your boiler with an air source heat pump (ASHP), you could slash your home’s carbon footprint by up to 65%. That said, making the transition from a traditional gas boiler to a heat pump is not cheap. The average UK ASHP installation cost £12,600 so far this year – according to the MCS.The good news is, government grants for heat pumps currently cover a decent chunk of that cost, with £7,500 available to households under the Boiler Upgrade Scheme. This means that replacing your gas boiler with a heat pump is now comparable in cost (to you), as replacing it with a like-for-like gas boiler would be. What’s more, with gas slowly being phased out of our energy mix, it’s a good idea to make the switch now, while the government is still willing to pick up the lion’s share of the bill.What’s on this page? 01 How did we choose? 02 Aira Heat Pump 12kW - best all-rounder 03 Grant Aerona³ R32 17kW - best for larger homes 04 Dimplex System H6 HTi70 8kW - best for efficiency 05 LG Therma V R32 Monobloc S 16kW - best value 06 Vaillant flexoTHERM 400v 19kW - best for power 07 Samsung EHS Mono HT Quiet - best quiet 08 MasterTherm UK BoxAir Inverter – best for durability 09 Daikin Altherma 3 H HT – best for hot water in cold weather 10 HydroPro ECO 12 – best for swimming pools 11 Key criteria explained 12 The best air source heat pumps at a glance 13 Next steps How did we choose?While all air source heat pumps work in much the same way, but there’s a surprising range of brands and sizes on the market these days. Choose wisely, and your heat pump will provide clean, green heating and hot water for years to come.With that in mind, it’s important to choose the right ASHP to suit your home, your energy needs and your budget – and we’re here to help you do that.Our team of experts analysed 22 of the top air source heat pumps available in the UK from 19 manufacturers and selected the best, based on key criteria, including: EfficiencyWarrantyPowerRange of sizes availableCold weather performanceCompactnessAestheticsValue for moneyTake a look at our picks, and find out which heat pump could be right for your home before getting a quote from a trusted installer. Aira Heat Pump 12kW – best all-rounder Swedish firm Aira has been making air source heat pumps for 20 years, but it’s only now arrived in the UK to shake up the heat pumps market, and it means business. Aira’s 15-year ‘Comfort Guarantee’ – a whopping five years longer than its closest rival – includes performance, product and installation warranties for full peace of mind. Thanks to a subscription-style plan that includes a smart monitoring app and maintenance, you don’t have to pay for the heat pump upfront. Aira’s engineers can even fix your system remotely via the app.The pump’s sleek black outdoor unit lives up to its good looks with solid performance ratings, including one of the best freezing weather operation scores in our test.Model featured12kWMin temp-25 °CTypical price (this model)From £3,000Energy ratingA++ to A+++Dimensions (W/H/D)1,152 x 1,503 x 416 mmModels available6, 8, 12kWEfficiency470%Warranty (years)15 Pros 15-year warranty beats all competitors by years Sleek black outdoor unit looks superb Efficiency and cold weather ratings are excellent Companion app lets you control thermostat, access features and troubleshoot Cons Biggest model is 12kW, which may be too small for larger homes Grant Aerona³ R32 17kW – best for larger homes The powerful 17 kW model of the Grant Aerona³ R32 offers a superb balance of performance, compactness and value for money. At 120 kg and just over £6,000, this relatively unobtrusive heat pump is powerful enough to provide heating and hot water for a detached house.If 17 kW exceeds your needs and budget, you can get the Aerona³ R32 in a wide range of smaller sizes. The 6 kW model measures less than 40 cm by 90 cm, weighs just 51 kg and costs around just £2,800.Whichever size you go for, the Grant heat pump delivers above-average efficiency, even when it’s -20°C outdoors, and comes with a seven-year warranty.Model featured17kWMin temp-20 °CTypical price (this model)£5,142Energy ratingA++ to A+++Dimensions (W/H/D)1,024 x 1,418 x 403 mmModels available6, 10, 13, 17kWEfficiency479%Warranty (years)7 (approved installer) Pros One of the best value for money heat pumps in our test Peak efficiency of 479% is well above average Surprisingly small and light for such a powerful heat pump Cons Seven-year warranty is good, but requires approved installation Looks more utilitarian than some rivals Dimplex System H6 HTi70 8kW – best for efficiency Most air source heat pumps have an efficiency rating of around 4.5 or 450%, which means they produce around four and a half times as much energy as they use. The Dimplex System H6 blows this standard out of the (hot) water – it can produce nearly six times the amount of energy it uses.Both sizes of the Dimplex System H6 are light and compact. The 8 kW model, which we looked at for this test, weighs just 94 kg and measures little over a metre across.Model featured8kWMin temp-20 °CTypical price (this model)POAEnergy ratingA++ to A+++Dimensions (W/H/D)1,035 x 1,075 x 450 mmModels available6, 8kWEfficiency572%Warranty (years)2 Pros The best efficiency on the market Built-in weather compensation technology keeps it working at -20°C Compact and light, ideal for homes with limited space Cons The H6 only comes in small sizes, but Dimplex also makes larger heat pumps Two-year warranty is well below average LG Therma V R32 Monobloc S 16kW – best value The LG Therma heat pump’s noise reduction technology makes it a fine choice for flats and other urban homes. Its lack of external refrigerant piping makes it easy to install, so it’s effectively a plug-and-play device.The Monobloc S, which comes in an unusually wide range of six sizes from 5kW to 16kW, is also a great fit for cold climates. It works in temperatures as low as -25, and performs at 100% of its capacity when it’s as cold as -10°C out.All this convenience comes at a relatively low price, with the most powerful 16kW model costing a typical £4,550 including VAT. That’s around the same as you’d pay for significantly smaller models of many rival heat pumps.Model featured16kWMin temp-25 °CTypical price (this model)£4,550Energy ratingA++ to A+++Dimensions (W/H/D)1,239 x 1,380 x 330 mmModels available5, 7, 9, 12, 14, 16kWEfficiency400%Warranty (years)7 (approved installer) Pros Great price for one of our top all-round heat pumps Works at -25°C, which is much better than industry average Seven-year warranty is among the best Uses environmentally-friendly R32 refrigerant Simple installation and quiet operation make it a convenient choice Cons Efficiency of 400% is at the bottom end of our top nine pumps Vaillant flexoTHERM 400v 19kW – best for power The flexoTHERM heat pump from boiler specialist Vaillant is one of very few pumps to be available in a 19 kW model, which is powerful enough to heat and provide hot water for a large detached house.This impressive machine, which can quickly heat water to 65°C, is also available in smaller, cheaper models from 5 kW upwards.All sizes of the flexoTHERM have an excellent seven-year warranty and a good efficiency rating that sees them produce nearly five times the energy they use.Model featured19kWMin temp-10 °CTypical price (this model)£8,229Energy ratingA++ to A+++Dimensions (W/H/D)600 x 1,183 x 595 mmModels available5, 8, 11, 15, 19kWEfficiency467%Warranty (years)7 (approved installer) Pros Huge range of sizes available, from 5 kW up to 19 kW Above average efficiency rating in all sizes Very compact for such a powerful heat pump Excellent seven-year product warranty Cons Doesn't perform at its best in freezing temperatures The 19 kW model is expensive, costing over £8,000 Samsung EHS Mono HT Quiet – best quiet Samsung’s sleek new heat pump excels on many fronts. It’s got one of the best efficiency ratings we came across, its cold weather operation is excellent, and it can produce water as hot as 70°C – just what you need for those steamy showers and baths in the depths of winter. Unlike many older heat pumps, the HT Quiet could replace your gas boiler altogether.What impresses us most, however, is the lack of noise from this handsome dark grey unit. Older heat pumps and air conditioners can be decidedly audible devices to live with, but the EHS Mono HT Quiet uses new-generation noise-reducing technologies to operate at levels as low as 35 decibels, which is quieter than most fridges.Given all these advantages, we were pleased to find that the mid-range 12kW model of Sasmung’s heat pump has a typical retail price tag of just over £4,000 including VAT, which makes it one of the best buys on our list.Model featured12kWMin temp-25 °CTypical price (this model)£4,060Energy ratingA+++Dimensions (W/H/D)1270 x 1018 x 530 mmModels available8, 12, 14kWEfficiency500%Warranty (years)7 Pros Runs as quietly as 35dB, which falls somewhere between a whisper and a fridge! Outstanding hot water levels, so it can potentially replace your boiler for good Excellent performance in low temperatures Dark grey unit looks stylish and modern Uses environmentally-friendly R32 refrigerant Cons Largest model in this range is 14kW, which is less powerful than some rivals in our rundown MasterTherm UK BoxAir Inverter – best for durability MasterTherm’s heat pump is at the premium end of the market. Unlike conventional heat pumps, it contains an inverter that ensures consistent temperatures without the unit having to keep stopping and starting. The result is a supremely durable device that should last much longer than its seven-year warranty guarantees.The MasterTherm is available in a range of sizes, but each size covers a range of power ratings. This gives you more freedom over which unit to choose. In our research we focused on the 5-13 kW model, which is powerful enough for most homes.Model featured5-13kWMin temp-20 °CTypical price (this model)POAEnergy ratingA++ to A+++Dimensions (W/H/D)1,300 x 1,495 x 526 mmModels available2-7, 3-9, 5-13, 5-17, 7-22 kWEfficiency520%Warranty (years)7 Pros Excellent seven-year warranty with no strings Based on inverter technology that delivers reliable, consistent heat Outstanding 520% efficiency Internet connected, with app for control and troubleshooting Cons Potentially very expensive, with kit versions costing £16,000 or more Daikin Altherma 3 H HT – best for hot water in cold weather Daikin’s sleek black heat pump excels in two compatible areas: providing piping hot water, and working in very low temperatures. So if you’re forever craving hot baths in winter, this is the heat pump for you.The Altherma 3 H HT, which comes in sizes from 8 kW to 18 kW, can supply water at temperatures up to 70°C – the same as gas boilers – and can do so when it’s a bitter -15°C outside.Like all heat pumps, the Daikin doesn’t produce quite as much heat when the mercury drops even lower. But it still works at -28°C, which no other heat pump can match.Model featured14kWMin temp-28 °CTypical price (this model)£4,838Energy ratingA++ to A+++Dimensions (W/H/D)595 x 1,650 x 625 mmModels available14, 16, 18kWEfficiency451%Warranty (years)5 (approved installer) Pros Simpler to install than many machines Supplies water at 70 °C – the same as gas boilers No need for new radiators or insulation Outstanding minimum operating temperature of -28°C Cons Only a five-year warranty with an approved installer HydroPro ECO 12 – best for swimming pools If you’re lucky enough to have a pool out the back, heating it will be one of your biggest uses of energy. To cut your bill and carbon footprint, invest in a heat pump to do the job.We chose the 12kW P12 because it’s significantly cheaper than most swimming pool heat pumps, costing around £1,550 plus installation – around half the price of most similar products.Model featured12kWMin temp11 °C (water temp)Typical price (this model)£1,502Energy ratingInfo not availableDimensions (W/H/D)390 x 600 x 100 mmModels available6kW - 26kWEfficiency480%Warranty (years)2 Pros Costs much less than most swimming pool heat pumps Efficient, producing nearly five times the energy it uses Very compact and light pump won't take up much garden space Available in a wide range of sizes from 6kW to an amazing 26kW Cons For swimming pools only Two-year warranty is the lowest in our test Key criteria explainedOur research team scrutinised the pros, cons and specifications of dozens of leading air source heat pumps. Then we chose our top nine according to key factors including value for money, efficiency, product warranty and minimum operating temperature. Here’s why these factors matter:EfficiencyA heat pump’s efficiency rating refers to the amount of energy (heat) it generates, versus the energy (electricity) it uses to run. The average pump is 300%-400% efficiency, but we found models that far exceed this. All our top nine have efficiency ratings of above 400%.WarrantyFive years is the average product warranty for heat pumps, but most of our top nine are guaranteed to last and perform for longer than this. Our best air source heat pump overall, the Aira Heat Pump, has a whopping 15-year product and performance warranty.Power and rangeThe bigger your house, the more powerful your heat pump needs to be. Most of the products we recommend are available in a range of sizes, from 5 kW (ideal for a flat) all the way up to 19 kW, which can heat a large household. Our favourite heat pumps come in a wide range of models, from low power to high power.Cold weather performanceAir source heat pumps can extract latent heat from the air even when it’s freezing outside. The best heat pumps have a minimum operating temperature of -20°C or colder. We rarely experience those temperatures in the UK, but a broad operating temperature is a good indication of a heat pump’s quality.CompactnessA typical 14 kW heat pump unit measures a metre or two across and weighs up to around 250 kg. That’s a lot of space on a balcony or in a small garden, so we’ve prioritised smaller, lighter heat pumps that don’t scrimp on power or efficiency.AestheticsA heat pump is a large device positioned against an outdoor wall of your home, so it is quite visible. As with the best solar panels, older and cheaper heat pumps have a utilitarian look, while newer models have a dark, sleek appearance that will soon have your neighbours asking where you bought yours.Value for moneyThe UK Boiler Upgrade Scheme covers up to £7,500 of the cost of buying and installing a heat pump (see Next steps below). The best heat pump installers will apply on your behalf for the grant, which rises to £9,000 in Scottish rural areas.So don’t just go for the cheapest heat pump you can find. Instead, look for great value for money. The models that rank highest in our rundown deliver the best performance, features and lifespan for their price. The best air source heat pumps at a glanceHere’s a handy comparison chart with the key specs of our top nine best heat pumps:Air source heat pump modelTypical priceSize (W/H/D)EfficiencyWarrantyBest forAira Heat PumpFrom £3,0001,152 x 1,503 x 416mm470%15 yearsAll roundGrant Aerona³ R32 17kW£5,1421,024 x 1,418 x 403mm479%7 years*Larger homesDimplex System H6 HTi70 8kWPOA1,035 x 1,075 x 450mm572%2 yearsEfficiencyLG Therma V R32 Monobloc 16kW£4,5501,239 x 1,380 x 330mm400%7 years*Quiet operationVaillant flexoTHERM 400v 19kW£8,229600 x 1,183 x 595mm467%7 years*PowerSamsung EHS Mono R32 16kW£3,223940 x 1,420 x 330mm442%3 years*On a budgetMasterTherm UK BoxAir Inverter A7W35POA1,300 x 1,495 x 526mm520%7 yearsDurabilityDaikin Altherma 3 H HT 14kW£4,838595 x 1,650 x 625mm451%5 years*Cold weatherHydroPro P12£1,502390 x 600 x 100mm480%2 yearsSwimming pools Find out how much a heat pump would cost for your home with our quick quote tool, and our trusted heat pump installers will be in touch. Also check out our article on heat pump costs, so that you know what to expect when discussing quotes. Next stepsIf you like the idea of switching to clean heating but don’t fancy paying several thousand pounds for a heat pump, we have good news. The government will pay a large chunk of it for you.The UK Boiler Upgrade Scheme (BUS), which applies to England and Wales, knocks £7,500 off the price of an air source heat pump and installation.To get your funding, first obtain around three quotes from professional installers. Fill in our quick quote tool and we’ll put you in touch with our trusted MCS-certified heat pump installers.Once you agree a quote with your installer, the value of the grant from the BUS will be deducted from the quote.In Scotland, Home Energy Scotland offers a £7,500 grant for air source heat pumps, or £9,000 in rural areas, plus an additional loan up to £7,500.What other types of heat pump are there?Water source heat pumps are even more efficient and powerful than air source heat pumps. However, you can only use a water source heat pump if you live near a body of water such as a lake, river or stream.Ground source heat pumps are more versatile. They’re also more consistent than air source heat pumps, because their output is affected less by the air’s temperature. On the downside, they’re more expensive than air source heat pumps, and much more invasive to install.To find out more, read our articles on water source heat pumps and ground source heat pumps. Written by: Jane Hoskyn Contributor Jane is a freelance journalist and copywriter who has spent many years reporting on the benefits of technology for consumers, businesses and our planet. Reviewed by: Roland Ellison Editor Roland is Editor of The Eco Experts. He is passionate about solar power, reducing plastic waste and technology that can help humanity overcome some of its greatest challenges.