A small box on the wall.
Indoors there is only a compact Light Box, 277 × 288 × 66 mm. The Sensys HD control and outdoor sensor are included. It pairs with a hot-water cylinder sized for your household, and it can also cool your home.
Warmth from the air, with a natural refrigerant.
Nimbus 5 is Ariston's new air source heat pump. It runs on R290, a natural refrigerant, heats radiators with water up to 75 °C, and comes in a compact, award-winning outdoor unit. We design it around your home, install it and look after it.
R290 natural refrigerant
Up to 75 °C for radiators
iF Design Award 2025
The Nimbus 5 outdoor unit, winner of the iF Design Award 2025.
5.1
COP, up to (A7/W35)1
A+++
Heating energy class, up to
75 °C
Maximum flow temperature
-25 °C
Heats down to this outdoor temperature
Why Nimbus 5
A cleaner heat pump that fits in.
Heating, hot water and, on suitable systems, summer cooling from one outdoor unit.
A natural refrigerant
R290 has a global warming potential of 0.02, close to zero.2 It is sealed inside the outdoor unit at the factory.
Works with radiators
Water up to 75 °C makes Nimbus 5 a strong boiler replacement. We check every room's radiator at the design temperature.
Quiet by design
Three programmable quiet levels lower the sound by 4, 6 or 8 dB(A), and an anti-vibration grille keeps the unit steady.
Compact and good-looking
The new outdoor unit won the iF Design Award 2025 and needs up to 40% less space than equivalent units.3
Control from your phone
Use the Sensys HD control on the wall, the Ariston NET app, Amazon Alexa or Google Assistant. Sensys HD can run up to six zones.
Ready for solar
With solar panels, Nimbus 5 can switch on while your panels are generating and store that electricity as heat and hot water.
Inside the outdoor unit
Built for cold, wet winters.
A frost-protection kit, drain pan and water filter are now built into the outdoor unit, so fewer parts are fitted outside your home.
- Defrosts only when needed
The defrost cycle starts only when ice is building up, so more of the unit's energy goes into heating your home.
- Cleaner system water
Magnetic and mechanical filters stop dirt building up and protect the system's efficiency.
- Three sizes, five outputs
Small (3 and 5 kW), medium (8 kW) and large (12 and 15 kW). We choose the size from your home's room-by-room heat loss.
Two ways to install
Pocket or Pack: matched to the space you have.
Both use the same Nimbus 5 outdoor unit. The difference is what goes indoors.
Everything in one cupboard.
A UK-made pre-plumbed cylinder with the pumps, valves and controls already fitted. Choose 150 L or 180 L slimline, or 210 L standard. It runs two heating zones and has a 3 kW immersion heater for back-up.
Help with the cost
A Boiler Upgrade Scheme grant of £7,500 or more.
Eligible air-to-water heat pump installations receive £7,500. If your property has no mains gas connection and you are replacing oil or LPG heating, the grant is £9,000 for applications properly made from 21 July 2026 to 31 March 2027. We check eligibility for your home.
Living with Nimbus 5
Set your comfort once, then forget about it.
With the Ariston NET app you can change temperatures, set schedules and check your energy use from anywhere.
Smart scheduling and geo-fencing adjust the heating around your routine. With remote assistance, your service partner can spot a problem early and often fix it without a visit. An annual service keeps the system efficient and your warranty valid.
Explore Comfort Care
How it works with Thermal Earth
From free survey to a warm home.
One local team designs, installs and supports your Nimbus 5.
Free estimate
Tell us about your home and get a first figure in minutes.
Free home survey
We measure heat loss, check your radiators and hot water, and find the best spot for the outdoor unit.
Design and install
We choose the right Nimbus 5 size and set-up. Our own team installs and commissions it.
Peace of mind
A 2-year workmanship guarantee from us, plus Ariston's warranty of up to 10 years.4
Common questions
Nimbus 5 FAQs
R290 is propane, a natural refrigerant with a very low global warming potential. In Nimbus 5 it is sealed inside the outdoor unit at the factory, and only water pipes come into your home. We install the unit with the clearances that Ariston and the standards require.
Often, yes. Nimbus 5 can heat water to 75 °C, but it is more efficient at lower temperatures. At the survey we check each room's radiator at the design temperature and tell you if any need upgrading.
Every air source heat pump has a fan, so none is silent. Nimbus 5 has three quiet levels that lower its sound by 4, 6 or 8 dB(A). We choose the position carefully and carry out the sound check your installation needs.
Nimbus 5 comes in 3, 5, 8, 12 and 15 kW sizes. The right one depends on your home's heat loss, which we calculate room by room at the free survey. Bigger is not better: a correctly sized unit runs more efficiently.
Nimbus 5 Pocket can run in reverse to cool your home through suitable underfloor or fan-coil systems with the right controls. Radiators are not designed for cooling. Ask us whether it makes sense for your home.
Start with your home
Is Nimbus 5 right for your home?
Get a free estimate in minutes, then book a free survey with our team.
- Coefficient of performance at nominal conditions A7/W35 to EN 14511. Running costs depend on the whole system, your tariff and how it is used.
- GWP 0.02, in line with EN 378 and the F-Gas Regulation.
- Ariston internal benchmark (November 2025) of outdoor unit footprint, comparing the Nimbus 5 50 M with equivalent EU models. Actual space saving varies by installation.
- Ariston warranty of up to 10 years, subject to Ariston's warranty terms and conditions.