Review · Heating
aroTHERM plus 7 kW
The default recommendation for a typical UK three-bed on the day the boiler retires; a genuinely propane-natured R290 monobloc with the quietest low-load behaviour in its class and an installer base wide enough to matter.
Review · Verified · Last reviewed 2026-07-17 · Evidence verified 2026-07-17
Right for
1930s and 1960s semis, and comparable end-terraces, where the fabric is decent and a 7 kW unit sizes cleanly; households who care about neighbourly noise as much as headline COP.
Wrong for
Rambling Victorian houses whose heat loss really needs 10 to 12 kW, and small well-insulated flats that a 5 kW unit would serve without oversizing.
How we assessed it
Method, not marketing
Read against MCS-installed monitored performance in the Electrification of Heat trial rather than manufacturer laboratory figures. Sizing checked against MIS 3005; running-cost framing indexed to the Ofgem cap in force at review date; grant treatment cross-read against Ofgem's Boiler Upgrade Scheme guidance.
Scored on four axes
Comfort in the room
5 / 5
Running character
4 / 5
Installation reality
4 / 5
Service life
5 / 5
Every score is defended in the finding it belongs to; a numeral is not an argument.
What we found
- 01
Low-load sound power is the quietest in the mainstream tier.
At the flow temperatures a properly sized system actually runs at through most of a UK winter, the aroTHERM plus modulates well below its rated output and the fan sits at a low steady speed; the perceived sound at a neighbouring bedroom window is a room-away conversation, not machinery.
Evidence · Manufacturer datasheet
- 02
R290 is the right refrigerant story for the next decade.
Propane has a global warming potential of three, against the several-hundred to low-thousand figures of the HFC blends it replaces; regulatory pressure on the older refrigerants is only going one way, and specifying R290 now avoids buying into a chemistry the market is already leaving.
Evidence · Independent reference
- 03
Real-world COP in a properly emitter-sized retrofit is around three.
The Electrification of Heat trial's monitored fleet average sat close to a seasonal COP of three across a wide range of house types; a competently installed aroTHERM plus on a sized-right emitter set clears that bar comfortably and pushes above it in the shoulder months.
Evidence · Independent reference
- 04
The grant maths still lands cleanly.
With the Boiler Upgrade Scheme paying seven thousand five hundred pounds off the installed cost, the aroTHERM plus lands within a few hundred pounds of a like-for-like premium gas replacement on a typical semi; the running-cost gap then favours the heat pump on any tariff with a decent unit-rate spread.
Evidence · Independent reference
What we would buy instead
- Ecodan PUZ-WM85
When the installer you trust locally is a Mitsubishi specialist; comparable performance, slightly different service network.
- Greenstar 4000 30kW Combi
When the fabric case for a heat pump has not yet been made and a modulating gas boiler is the honest bridge for the next five to seven years.
The evidence behind this guide
Sources for the factual claims on this page.
Sources support factual claims about aroTHERM plus 7 kW. They do not stand in for editorial judgement; the verdict, suitability calls and price stance on this page are our view, labelled as such. If the evidence weakens, so does the confidence rating.
Evidence verified · 2026-07-17
Official register
- MIS 3005: Heat Pump Systems
MCS · Accessed 2026-07-17
Supports · Technical claim · Primary
- Boiler Upgrade Scheme guidance
Ofgem · Accessed 2026-07-17
Supports · Technical claim · Primary
Independent publication
- Electrification of Heat: Final Report
Energy Systems Catapult · Accessed 2026-07-17
Supports · Technical claim · Primary
Manufacturer information
- Vaillant aroTHERM plus air source heat pump
Vaillant UK · Accessed 2026-07-17
Supports · Technical claim · Product range · Secondary
The default recommendation for a typical UK three-bed on the day the boiler retires; a genuinely propane-natured R290 monobloc with the quietest low-load behaviour in its class and an installer base wide enough to matter.