Daikin Altherma heat pumps

What a Daikin Altherma does

Daikin Altherma is Daikin’s range of air-to-water heat pumps. An outdoor unit takes heat from the outside air and passes it into water, which then runs through your radiators or underfloor heating and heats a hot water cylinder. It replaces a gas, oil or LPG boiler as your main heating.

That makes it different from Daikin’s split air conditioning, which heats and cools the air in a room directly. If you’re not sure which you need, our guide to the difference between heat pumps and air conditioning sets it out.

The current Altherma range

Daikin’s newest generation is Daikin Altherma 4 H. In its launch announcement Daikin says it uses R290 (propane), a natural refrigerant with a very low GWP, comes in 6, 8, 10, 12 and 14 kW classes in single and three-phase versions, can produce hot water up to 75°C and keeps working down to an outdoor temperature of -28°C. Smaller sizes were announced in hydrosplit and monobloc versions.

Daikin continues to offer R32 Altherma heat pumps for homes where an R290 unit can’t be used. Across the range you’ll see two layouts:

• Monobloc: all the refrigerant stays in the outdoor unit, and only water pipes come into the house.
• Split or hydrosplit: part of the system sits indoors with the water side and controls, which can help where space outside is tight.

We recommend a model and size after a heat loss calculation, not from a brochure.

Will it work with my radiators?

Heat pumps are most efficient when they run at lower water temperatures than a typical boiler. Higher-temperature units such as the Altherma 4 H can reach higher flow temperatures, which helps in some older homes, but running hotter costs efficiency. So we look at every room: its heat loss, the size of the radiator in it, and whether a few radiators need upsizing. Insulation and draught-proofing first often make the biggest difference.

Underfloor heating suits heat pumps well because it runs at low temperatures across a large surface.

The £7,500 Boiler Upgrade Scheme grant

In England and Wales, the Boiler Upgrade Scheme gives £7,500 towards an air source (air-to-water) heat pump. The installer must be MCS certified and applies for the grant; it comes off your bill. The main conditions:

• One grant per property, and not to replace an existing low-carbon heating system.
• Hybrid systems (a heat pump working alongside a boiler) are excluded.
• Until March 2027 an extra £1,500 is available for air source or ground source heat pumps in homes heated by oil or LPG with no mains gas.

Our air-to-water heat pump prices are £8,000–£16,000, with 0% VAT on homes, before the £7,500 grant. Under HMRC Notice 708/6, installing a heat pump in a home is zero-rated until 31 March 2027, then 5%. This is general information, not tax advice.

Planning and noise

On a house in England, an air source heat pump can be permitted development if it meets the limits, including an outdoor unit (with housing) of no more than 1.5 m³ and compliance with MCS 020(a), which includes a noise check. Listed buildings, conservation areas, flats and Article 4 areas have extra rules. We check this at the survey.

Controls and the Onecta app

Daikin says the Altherma 4 H has a 5-inch colour touch screen and works with the Onecta app, which lets you check energy use and change your home’s temperature from your phone. It’s also prepared for remote connection, so settings can be adjusted without a site visit where you agree to that.

Daikin warranty on Altherma

Daikin gives a standard 2-year warranty on its air-to-water heat pumps. Its UK warranty page explains that, once the installer has registered the unit on Daikin’s Stand By Me portal, the homeowner can extend this to 5 years at no extra cost, and that a 7-year option is linked to Daikin’s own installer programme. Annual maintenance is a condition, and Daikin may ask for proof. You have 2 years from commissioning to activate an extension.

We don’t claim a Daikin installer status or add a warranty of our own. We register the unit where we can, explain the manufacturer’s terms on your quote and keep the service records.

From survey to switch-on

1. Survey: we measure the rooms, check the radiators, pipework and insulation, and agree where the outdoor unit and cylinder will go.
2. Design and quote: a room-by-room heat loss calculation, the Altherma model and size, any radiator changes and a fixed price, with the grant and VAT shown clearly.
3. Grant: we apply for the Boiler Upgrade Scheme grant once you’ve accepted the quote.
4. Installation: the outdoor unit, cylinder, controls and any new radiators go in, and the old boiler is disconnected.
5. Commissioning and handover: we set the system up, show you the controls and the Onecta app, and give you the MCS certificate and paperwork.

Strengths and things to consider

Strengths: a newer R290 generation with high flow temperatures; monobloc and split options; and an app that shows energy use.

Things to consider: R290 is flammable, so outdoor unit siting has rules of its own; a heat pump needs a hot water cylinder, so you need space for one; and good results depend on design, not the badge. Compare it with the Mitsubishi Ecodan on your survey.