Vaillant Heat Pumps in the UK

Vaillant's main UK heat pump is the aroTHERM plus, a propane (R290) monobloc sold in 3.5, 5, 7, 10 and 12kW outputs, and the outdoor unit alone costs roughly £3,800 to £4,200 including VAT at UK merchants. Add the indoor kit and a 7kW unit with a uniTOWER cylinder reaches £7,545.60 including VAT at City Plumbing, checked on 6 October 2026. The headline "7 year warranty" is real but conditional, Vaillant publishes at least four different "sound power" figures for the same range, and only one of them is the figure your council will use. All three of those are worth ten minutes before you sign, and the rest of this guide is each one in turn.

There are three different Vaillant heat pumps, and your quote may not say which

Vaillant currently sells the aroTHERM plus, the newer and more compact aroTHERM pro, and the aroTHERM split, and they are not interchangeable. A quote that says only "Vaillant aroTHERM" has not told you what you are buying.

• aroTHERM plus. The flagship monobloc. R290 refrigerant, flow temperatures up to 75°C, outputs of 3.5, 5, 7, 10 and 12kW. Model codes run VWL 35/6, VWL 55/6, VWL 75/6, VWL 105/6 and VWL 125/6, with an S2 suffix on the current generation.
• aroTHERM pro. Newer, single fan, more compact, also R290. Vaillant's own product page gives it an output range of 5 to 11kW and describes it as its most compact heat pump.
• aroTHERM split. A split system on R32 rather than R290, which means the installer needs F-gas certification to fit it. Midsummer Wholesale states exactly that on its Vaillant page, and asks for evidence of F-gas certification before supplying one.

One more detail worth knowing: Vaillant's own installer quick guide lists a VWL 65/6 S2, a roughly 6kW unit, and marks it "not available in the UK" three separate times. If a quote names a 65/6, query it.

The model code also tells you something the kW number does not. The number in the name is a nominal rating, not the output at your design temperature. Vaillant's published output table shows the 5kW unit delivering 6.3kW at minus 5°C outside with a 35°C flow, and the 12kW unit delivering 13.1kW in the same conditions. Both numbers fall as the flow temperature rises. Sizing is settled by a room-by-room heat loss calculation to MCS MIS 3005, not by the badge, and Vaillant's guide prints the design temperatures the calculation uses: minus 3.4°C for Birmingham, minus 3.9°C for Glasgow, minus 1.8°C for London, minus 0.2°C for Plymouth.

What a Vaillant heat pump costs in the UK right now

At UK merchants on 6 October 2026, the aroTHERM plus outdoor unit on its own runs from about £3,830 to £4,190 including VAT, and the same unit bundled with the indoor cylinder tower roughly doubles that. These are kit prices, not installed prices, and the gap between them is the point.

Read those two 7kW lines together. The outdoor unit and an interface come to about £4,420. The same outdoor unit supplied with a uniTOWER comes to £7,545.60, so the indoor half of a Vaillant system is roughly £3,100 of kit on its own. That is not an upsell, it is a hot water cylinder plus the hydraulics and the back-up heater, and a monobloc heat pump cannot make hot water on demand the way a combi boiler does. But it does mean that two Vaillant quotes can differ by three thousand pounds of equipment and both be honest, and the only way to see it is an itemised quote that names the indoor unit.

Set that against the whole job. The Energy Saving Trust's typical figure for installing an air source heat pump is around £12,000, which we work through in detail in our guide to heat pump costs in the UK. On the 7kW Vaillant numbers above, the kit is somewhere between a third and two thirds of that, and the balance is labour, the electrical work, radiator changes, pipework and the survey. A quote that is well under £12,000 on a Vaillant system is a quote to read line by line, not a bargain to grab.

The "7 year warranty" is three warranties, and only one of them is 7 years

Vaillant's standard guarantee on the aroTHERM plus is 2 years. The 5 year and 7 year terms exist, but both depend on your installer's loyalty tier, and the 7 year term also requires a Vaillant hot water cylinder. This is Vaillant's own published guarantee table, read live on myVaillant Pro on 6 October 2026:

Two conditions sit underneath all of it. The installer has to register the appliance within 30 days of installing it, and the homeowner has to arrange an annual service to keep the guarantee valid. Miss either and you are back towards the 2 year term, whatever the sales brochure said.

So the question to ask is not "does it come with 7 years". It is three questions: which myREWARDS tier are you, are you fitting a Vaillant cylinder, and will you register it inside 30 days. All three have to land for the 7 to be real, and only your installer can answer them. A third-party installer page saying "7 year Vaillant warranty" is describing their own tier, not the product.

It also explains why a Vaillant quote often arrives with a Vaillant uniSTOR or uniTOWER cylinder rather than a cheaper third-party one. That is the warranty condition doing the work, not necessarily a worse deal. Just price it as what it is: roughly £3,100 of indoor kit buying you five extra years of cover.

The paid extension is an annual fee, not a one-off

Beyond the registered guarantee, Vaillant sells Cover and Care packages. On vaillant.co.uk on 6 October 2026 they are listed at £295 for the 5 year plan, £305 for the 7 year plan and £312 for the 10 year plan, and the footnote under the table reads "all annual fees include VAT and may be subject to change and/or annual price increases". Read as an annual fee, the 5 year plan is around £1,475 across its term rather than £295, so confirm the basis in writing before you sign up to one.

Two eligibility conditions catch people out. The heat pump must be less than 18 months old and have been registered within 30 days. And if you take the package out after the first 12 months, you pay for both an Appliance Function Check and your first service at the same time to qualify.

The same 5kW unit is 46% more efficient at 35°C than at 55°C

Vaillant's published SCOP for the aroTHERM plus ranges from 5.03 down to 3.06 across the range, and the variable that moves it most is flow temperature, which is decided by your radiators. From Vaillant's own installer quick guide:

The 5.03 in Vaillant's marketing is the 10kW unit at a 35°C flow. The same brochure range also contains a 3.06. That spread is the whole running cost argument in one table, because on the Ofgem price cap for 1 October to 31 December 2026 a heat pump needs a seasonal efficiency of roughly 3.0 to match a 90% efficient gas boiler. We set that calculation out in full on the heat pump cost page. A 5kW aroTHERM plus running at 55°C because nobody resized the radiators is sitting on the break-even line. The same unit at 35°C is comfortably past it.

Vaillant says as much itself. Its installer page states that the aroTHERM plus "is designed to operate at a low flow temperature in line with MCS installation standards" and that "the ideal heat pump flow temperature should range between 35 to 55°C", with the higher end reserved for hot water and legionella control rather than space heating. The 75°C figure in the headlines is a hot water capability, not an operating setting for your radiators.

So the thing to ask for is not a SCOP. It is the design flow temperature on your heat loss calculation. Anything at or below 45°C and the Vaillant numbers above are working for you. At 55°C, the kit is fine and the system design is the problem.

The sound power figure that decides whether it is permitted development

England's permitted development right for an air source heat pump now requires the sound calculation in MCS 020 a), and the pass mark is 37.0 dB(A) at the neighbour's window, not the 42 dB(A) figure still printed on many council pages. Article 6 of The Town and Country Planning (General Permitted Development) (England) (Amendment) Order 2025 rewrote the definition of "MCS Planning Standards" in Part 14 of the 2015 Order, swapping the reference to MCS 007 for MCS 020 a) Issue 1.1, in force from 29 May 2025. The 42 dB(A) figure belongs to the older version of the standard, which added an assumed 40 dB background level to reach a combined permitted level. The current document does not: paragraph 1.2 states the limit as 37 dB LAeq,5mins, and step 8 of the calculation asks whether the result is "equal to or lower than 37.0 dB(A)". If a council page or an installer quotes you 42, check the date on it.

This matters for a brand page because step 3 of the calculation is the manufacturer's A-weighted sound power level, and Vaillant publishes several different ones. Here are the figures circulating on live pages today:

• 44 dB(A) as low as, on The Heat Pump Warehouse's Vaillant listings
• 48 dB(A) as low as, on the myVaillant Pro aroTHERM plus product page
• 54 dB(A) as low as, on Vaillant's own professional aroTHERM plus landing page, stated twice

None of those is what the calculation uses. The figures that matter are the per-model, per-test-condition sound power levels in Vaillant's installer quick guide, measured to EN 12102 and EN 14511:

The distances are MCS 020 a)'s own formula applied to Vaillant's own figures, for the most common siting in a British garden: unit on the ground against one wall, no solid barrier, clear line of sight to the assessment position. The assessment position is defined in the standard as 1 metre outside the centre of any door or window to a habitable room of a neighbouring property, which in a terrace or a tight semi is often closer than people assume.

Three consequences follow, and they are all practical.

First, the jump from the 7kW to the 10kW is not just a bigger unit and a bigger bill. On Vaillant's numbers it nearly doubles the clear distance you need. An oversized Vaillant can fail permitted development in a garden where a correctly sized one passes.

Second, a wall helps enormously. MCS 020 a) allows a 10 dB reduction for a solid brick or masonry barrier that completely blocks the line of sight, which takes the 60 dB(A) case from about 8 metres down to about 2.6 metres. An open fence, a fence with gaps, a hedge or planting count for nothing in the standard. Vegetation is explicitly excluded.

Third, and this one gets missed: the standard states that "the sound power level in low noise mode shall not be used". Vaillant's own tables show the 3.5 and 5kW units dropping from 50.4 dB(A) to 41.4 dB(A) of sound pressure at 1 metre when the compressor is held at a 60% speed reduction. That quiet mode is real and useful on a summer night. It cannot be used to get a unit through planning. Samsung's UK range is the starkest version of the same problem: it is advertised at "as low as 35 dB(A)" while the figure the standard takes for its 16kW unit is 65.

On the Quiet Mark accreditation Vaillant advertises, both Vaillant sources say the same thing and it is worth noticing what they do not say. The myVaillant Pro page and the installer quick guide both list the accredited outputs as 3.5, 5, 7 and 12kW. The 10kW is in neither list, despite sharing the 60 dB(A) rating with the 12kW. Our guide to permitted development for solar panels covers the equivalent rules on the solar side, where noise is not a factor at all.

R290 is propane, and it changes where the unit can go

The aroTHERM plus uses R290, which is propane, with a Global Warming Potential of 3 and a charge of 0.6 to 1.3kg depending on output. The low GWP is the headline, and it is genuine: R290 sits outside the F-gas restrictions tightening around R410A and R32. The flammability is the trade-off, and it shows up as a siting constraint rather than a risk you manage day to day.

Vaillant's installer guide defines a protective zone around the unit and is specific about what cannot be in it: "there must be no ignition sources, such as plug sockets, light shafts, lamps or electrical switches in the protective zone". Minimum clearances in the guide run to 2,100mm and 3,100mm on two of the measured dimensions and 1,000mm on another. Air vents to void areas and air-tight drains are allowed inside the zone, as are open gullies and downpipes.

In practice that rules out a few places homeowners suggest first: directly under an outside light, beside an external socket, or in a tight lightwell. MCS 020 a) independently rejects the lightwell, because a heat pump with more than three reflective surfaces cannot meet the standard at all.

One more live inconsistency on Vaillant's own pages, for completeness. The myVaillant Pro product page states that R290 has "a very low Global Warming Potential (GWP) of just 0.02". Vaillant's professional landing page, the installer quick guide and Midsummer Wholesale all state 3. The datasheet figure of 3 is the correct one, and it is the number on the technical data table alongside a CO2 equivalent of 0.0018 to 0.0039 tonnes.

Does a Vaillant heat pump get the £7,500 grant?

Yes, if the product is MCS certified and the installer is an MCS certified contractor, because the Boiler Upgrade Scheme is installer-led rather than something you apply for. Read live on gov.uk on 6 October 2026, the scheme pays £7,500 towards an air source heat pump in England and Wales, one grant per property, with an additional £1,500 until March 2027 if the property is heated by oil or LPG and has no mains gas connection. Hybrid systems combining a gas boiler with a heat pump are not eligible.

On the product side, City Plumbing's own technical specification for the aroTHERM plus 7kW with uniTOWER lists "Standards Met: MCS" and "Certifications Met: MCS", and Vaillant states that its aroTHERM range is MCS accredited. Do not take either on trust for the exact model on your quote: the MCS product directory is searchable and is the register the scheme actually works from. MCS 020 a) also names the MCS product database as one of the three places the sound power level may be taken from, alongside the product fiche and the energy label, so checking it answers two questions at once.

Scotland and Northern Ireland do not use the Boiler Upgrade Scheme. Scotland has the Home Energy Scotland Grant and Loan instead, and Northern Ireland has no specific heat pump grant at the moment. The heat pump cost guide sets out all three positions, and the numbers underneath them.

VAT is 0% on installing a heat pump until 31 March 2027, after which it reverts to 5% rather than 20%. The same zero rate and the same deadline apply to solar panels and home batteries, which we cover in detail in our guide to VAT on solar panels.

Ideal's Logic Air range is published with up to a 7 year parts and labour warranty, available when the unit is registered within 30 days of installation and serviced annually. Our guide to Ideal heat pumps in the UK sets out the Logic Air prices, its published efficiency figures at a 35°C and a 55°C flow temperature, and its sound power levels.

Midea's heat pumps reach the UK through approved distribution partners, and Midea says its products are not available to end users. Midea publishes up to a 10 year warranty on the M Thermal R32, which extends annually when the original Mi Pro installer registers maintenance. Our guide to Midea heat pumps in the UK covers the M Thermal R32, the M Thermal R290 and the indoor H-Pack, with merchant prices for the M Thermal R32.

Viessmann words its cover differently again: its warranty table gives the Vitocal 150-A a 2 year standard warranty, and a 7 year extension is a £360 purchase your installer registers. Our guide to Viessmann heat pumps in the UK sets out the Vitocal range, merchant prices for the 150-A and 151-A, and the flow temperatures by model.

Stiebel Eltron sets standard cover at 2 years parts and labour, with an additional 5 years parts and labour available on conditions set at installation, including a complete Stiebel Eltron system and registration by a partner installer within four weeks of the first start-up. Our guide to Stiebel Eltron heat pumps in the UK sets out that condition list, the HPA-O Trend specification and the company's own published service prices.

If Vaillant is on your quote, the other brand on the shortlist is usually Daikin, and the two make a useful comparison because Daikin's monoblocs are noticeably louder on the figure planning uses. Our guide to Daikin heat pumps in the UK runs the same sound power calculation on the Altherma range and sets out Daikin's own two, five and seven year warranty ladder.

Five things on a Vaillant quote that cost money and are easy to miss

All five come from Vaillant's own installer documentation, and none of them tend to appear in a one-page quote.

• A type B RCD. Vaillant's technical data carries a bolded note: "all Vaillant heat pumps must be installed with a type B RCD rated to 20kHz or greater and with a minimum trigger point of 150mA above 1kHz". Vaillant sells complete RCD consumer units for the purpose at £508.58 and up on the trade list. This is an electrical line item, not an accessory.
• Minimum open water volume. 15 litres for the 3.5 and 5kW, 20 litres for the 7kW, 45 litres for the 10 and 12kW, needed so the unit can defrost without short cycling. If your system holds less, a buffer tank goes in, and Vaillant's own 45 litre buffer is £704.86 on the trade list.
• Wall mounting only goes so far. Vaillant's mounting accessories note that its wall brackets are "only suitable for 3.5/5 and 7kW models". The 10 and 12kW units weigh 194kg and 210kg and stand 1,565mm tall, so they go on the ground.
• Cylinder compatibility is a matrix, not a free choice. Vaillant's table pairs the 3.5kW with 150 or 200 litre uniSTOR cylinders only, the 7kW up to 300 litres, and the 12kW from 200 litres upward. If the 7 year guarantee depends on a Vaillant cylinder, this table decides which one.
• Three phase on the big units. The 10 and 12kW come in 230V and 400V versions, and the 400V ones need a three phase supply. Fuse sizes are 16A up to 7kW and 25A on the 10 and 12kW.

So should you accept the Vaillant quote?

On the equipment, there is not much to argue with. R290 at a GWP of 3, published SCOPs between 3.06 and 5.03, operation down to minus 25°C, A+++ at a 35°C flow, salt resistant construction rated for installations within 150 metres of the sea, and a UK service operation behind it. It is a mainstream choice for good reasons.

The things worth pushing on are not about Vaillant. They are about the quote in front of you.

Get the model code, not the brand. Get the design flow temperature, because that is what turns a 4.48 into a 3.06. Get the sound power figure and the MCS 020 a) calculation in writing if the unit is going anywhere near a boundary, especially on a 10 or 12kW. Get the guarantee term stated with the condition attached to it, because 2, 3, 5 and 7 years are all technically true statements about the same heat pump. And get the indoor side itemised, because that is where three thousand pounds hides.

If you are weighing a heat pump against or alongside solar, the two interact less than people hope and more than people fear. A heat pump's demand peaks in the British midwinter, which is when a solar array produces least, so solar will not run your heating in January. What it does is carry the shoulder months and the hot water, and a battery lets you buy winter electricity in the cheap overnight window. Start with solar panel costs in the UK and solar battery storage, and note that the same 0% VAT deadline of 31 March 2027 applies to all three technologies. Our guide to the cost of electricity per kWh tracks the rate that decides whether any of it pays.

Frequently asked questions