Vaillant aroTHERM plus vs Worcester Bosch: Which Air Source Heat Pump Is Better? (2026)
Quick Verdict
Vaillant aroTHERM plus is the more efficient choice on its MCS-certified figures, with lower estimated running costs, while Worcester Bosch is more budget-friendly with pre-grant pricing from £9,000 (the £7,500 grant applies equally to both in England and Wales).
Side-by-Side Comparison
| Feature | Vaillant aroTHERM plus | Worcester Bosch |
|---|---|---|
| Installed price (before grant) | £10,000 - £16,000 | £9,000 - £14,000Lower |
| After £7,500 grant (illustrative, England and Wales) | £2,500 - £8,500 | £1,500 - £6,500 |
| SCOP at 35°C (MCS) | 4.88Higher | 4.54 |
| SCOP at 55°C (MCS) | 3.63Higher | 3.29 |
| Largest size | 12kWLarger homes | 7kW |
| Standard warranty | 2 years | 2 years |
| Longest warranty (conditions apply) | 7 years | 7 years |
| Sound power (declared) | 55 dB(A) | 42 dB(A)Lower |
| Annual running cost (est., 45°C flow) | ~£620/yrLower | ~£670/yr |
| Refrigerant and max flow | R290, up to 75°C flow | R290, up to 75°C flow |
| Country | Germany | UK |
| UK brand | No | Yes |
| Best for | Efficiency-first buyers who want a proven, widely monitored unit | Homes where noise matters most, or Worcester boiler owners staying with the brand |
Specifications and pricing are indicative for the UK market as at June 2026. Post-grant figures illustrate the £7,500 Boiler Upgrade Scheme in England and Wales (Scotland uses the Home Energy Scotland grant and loan; Northern Ireland has no equivalent). Running costs assume ~10,000 kWh of heat a year at 26.32p/kWh (Ofgem cap average, October to December 2026; changes quarterly). Confirm current models and exact pricing with your MCS-certified installer.
Model by Model, Size for Size
Each Vaillant aroTHERM plus model against the nearest Worcester Bosch size. Better figure in green.
| 7 kW vs 7 kW | aroTHERM plus 7kWR290 · VWL 75/6 A 230V S2 | Compress 5800i AW 7kWR290 · CS5800i 7 OR-S |
|---|---|---|
| SCOP at 35°C (MCS) | 4.36 | 4.54 |
| SCOP at 55°C (MCS) | 3.39 | 3.29 |
| Sound power (declared) | 55 dB(A) | 42 dB(A) |
| Maximum flow temperature | 75°C | 75°C |
| Running cost (est.) | ~£680/yr | ~£670/yr |
| Installed price from (before grant) | £10,000 | £9,000 |
| Outdoor unit weight | 128 kg | 143 kg |
| Suits | 3 bed semis and well-insulated homes | 3 bed homes |
Sizes are the makers' labels; where a label is not the rated output, the brand page says what is. Prices are PumpSwap's indicative estimates. Running costs use the same basis as the table above.
Price Comparison
Vaillant aroTHERM plus starts from £10,000 installed before any support (indicative, June 2026), while Worcester Bosch starts from £9,000. That is a difference of roughly £1,000 at the entry level. Worcester Bosch is the more budget-friendly option upfront, though Vaillant aroTHERM plus may claw some of that back through running costs over time. Both are installed prices in GBP with 0% VAT (until 31 March 2027) already applied. In England and Wales the £7,500 Boiler Upgrade Scheme grant comes off both equally, so the pre-grant difference carries straight through: illustratively £2,500 - £8,500 for Vaillant aroTHERM plus and £1,500 - £6,500 for Worcester Bosch out of pocket. Your MCS-certified installer claims the grant for you.
Efficiency Comparison
SCOP (seasonal coefficient of performance) is the key efficiency measure for a heating heat pump: the kilowatt-hours of heat you get per kilowatt-hour of electricity across a whole heating season. The figures here are MCS-certified, at 35°C flow (underfloor heating or large radiators) and 55°C (hotter radiators). Vaillant aroTHERM plus is certified at 4.88 at 35°C and 3.63 at 55°C, while Worcester Bosch is certified at 4.54 and 3.29. On our estimates at a 45°C design flow temperature, the Vaillant aroTHERM plus costs about £50 a year less to run at Ofgem cap electricity prices, or approximately £500 over ten years. Real-world efficiency depends heavily on system design and flow temperature, which is what the MCS heat loss survey is for.
Warranty Comparison
Vaillant aroTHERM plus: 2 years as standard; up to 7 years with a Vaillant cylinder through a Platinum, Renewable Partner or myREWARDS installer. Register within 30 days and service annually. Worcester Bosch: 2 years as standard; up to 7 years through the installer route, registered within 30 days of commissioning, with annual servicing. Workmanship cover for the installation itself comes separately from your installer and should be in writing.
Noise Comparison
Noise matters in UK homes because the outdoor unit often sits close to a neighbour's boundary or a bedroom window. The like-for-like figure is the maker's declared sound power: the noise the unit itself emits. Vaillant aroTHERM plus: 55 dB(A). Worcester Bosch: 42 dB(A). On paper the Worcester Bosch is quieter by 13 dB(A). What a neighbour hears is much lower and falls with distance, and permitted development rules require the installation to meet the MCS noise standard at their window, so siting matters as much as the unit.
Cold-Weather and Retrofit Suitability
Two things decide how well a unit suits an older UK home: cold-weather output and flow temperature. Vaillant aroTHERM plus uses R290 refrigerant (up to 75°C flow), while Worcester Bosch uses R290 (up to 75°C flow). Both reach 70°C or more, so both can work with existing radiators; the decision comes down to price, warranty and installer availability. Modern units hold useful output well below freezing. In the colder parts of the UK (Scotland and northern England in particular), frosty mornings trigger short defrost cycles that trim efficiency, so ask each installer for low-temperature output figures and take the MCS heat loss survey seriously; radiator upsizing is more commonly recommended there so the system can run at efficient flow temperatures.
Pros and Cons
Vaillant aroTHERM plus
Pros
- Natural R290 refrigerant, up to 75°C flow
- Quiet Mark certified (except the 10 kW)
- Among the best measured real-world efficiency on heatpumpmonitor.org (median 4.06)
Cons
- Standard warranty is 2 years; 7 needs a Vaillant cylinder and a partner installer
- The /6 range is being replaced by a new model launched in June 2026
- The 12kW outdoor unit is tall (1,565 mm) and heavy (194 kg)
Worcester Bosch
Pros
- Declared sound power of 42 dB(A) for the 7 kW
- Natural R290 refrigerant, up to 75°C flow
- Selling heat pumps in the UK since 2006
Cons
- Standard warranty is 2 years; 7 needs registration and annual servicing
- Heavy for a 7 kW unit (143 kg)
Which Should You Choose?
Choose Vaillant aroTHERM plus if...
- You want the higher certified efficiency (SCOP 4.88 vs 4.54 at 35°C, MCS)
- You want lower estimated annual running costs (~£620/yr vs ~£670/yr)
Choose Worcester Bosch if...
- You want a lower upfront cost (from £9,000 vs £10,000 before the grant)
- A lower declared sound power matters to you (42 vs 55 dB(A))
- You want a UK brand with local manufacturing or headquarters behind it
The grant is the same, whichever brand you pick
Every air-to-water unit on this page qualifies for the £7,500 Boiler Upgrade Scheme grant in England and Wales (£9,000 for oil and LPG heated homes until March 2027) when fitted by an MCS-certified installer, who claims it on your behalf so it comes straight off the quote. Scotland uses the Home Energy Scotland grant of up to £7,500 (£9,000 rural and island) plus an optional interest-free loan; Northern Ireland currently has no equivalent scheme. 0% VAT on residential installations applies UK-wide until 31 March 2027. Accurate as at July 2026.
Heat pump guides
- Air source heat pump installation cost in the UK
- The best air source heat pumps in the UK, compared
- The £7,500 Boiler Upgrade Scheme, explained
- Air source heat pumps: costs, grants and brands
- Heat pump grants in London
- Heat pump grants in South East England
- Heat pump grants in South West England
- Heat pump grants in East of England
- Heat pump grants in East Midlands
- Heat pump grants in West Midlands
- Heat pump grants in Yorkshire and the Humber
- Heat pump grants in North West England
- Heat pump grants in North East England
- Heat pump grants in Scotland
- Heat pump grants in Wales
- Heat pump grants in Northern Ireland
Where are you?
See indicative costs and local installers for your area