Head to head
Vaillant aroTHERM plus 5kW vs Worcester Bosch Greenstar 4000 25kW combi
The Vaillant aroTHERM plus 5kW is a r290 monobloc air source heat pump, 5 kw heat output. The Worcester Bosch Greenstar 4000 25kW combi is a gas combi boiler, 25 kw hot water output.
Last reviewed 13 September 2026
Specifications side by side
| Vaillant aroTHERM plus 5kW | Worcester Bosch Greenstar 4000 25kW combi | |
|---|---|---|
| Dimensions | 965 x 1100 x 450 mm (H x W x D) | 710 x 400 x 310 mm |
| Weight | 128 kg (operating) | 32.0 kg |
| Heat output | 5 kW | - |
| SCOP | up to 5.03 | - |
| Refrigerant | R290 (propane), low GWP | - |
| Sound power | 53 dB(A) at A7/W35, 58 dB(A) at A7/W55 | - |
| Max flow temperature | 75C | - |
| Hot water output | - | 25 kW |
| Central heating output | - | 25 kW |
| ErP class | - | A |
| Seasonal efficiency | - | 94% |
| Warranty | - | 10 years |
| Hot water flow rate | - | 10.5 litres per minute |
Sources: Vaillant aroTHERM plus 5kW, Worcester Bosch Greenstar 4000 25kW combi. Figures vary by model year and options, so check with the supplier before you commit.
Buy or hire the aroTHERM plus 5kW if...
The smallest aroTHERM plus, sized for a well-insulated flat or small house. It uses the natural refrigerant R290 rather than an F-gas, and reaches a 75C flow temperature, which helps it work with existing radiators on a retrofit job.
Full aroTHERM plus 5kW specifications →Buy or hire the Greenstar 4000 25kW combi if...
A gas combi boiler with 25 kW of hot water output, sized for a flat or small house with one bathroom. It delivers about 10.5 litres per minute of hot water, which decides how well a shower runs while a tap is on. Warranty: 10 years. Seasonal efficiency is 94%.
Full Greenstar 4000 25kW combi specifications →Common questions
What is the difference between the Vaillant aroTHERM plus 5kW and the Worcester Bosch Greenstar 4000 25kW combi?
The Vaillant aroTHERM plus 5kW is a r290 monobloc air source heat pump, 5 kW heat output; the Worcester Bosch Greenstar 4000 25kW combi is a gas combi boiler, 25 kW hot water output.
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