Head to head
Baxi 600 Combi 2 30kW vs Worcester Bosch Greenstar 4000 25kW combi
The Worcester Bosch Greenstar 4000 25kW combi comes with 3 years more warranty and puts out 4kW more to the radiators. The Baxi 600 Combi 2 30kW has 6kW more hot water output and runs 1.7 litres a minute more hot water.
Last reviewed 13 September 2026
Key differences
- Warranty: the Worcester Bosch Greenstar 4000 25kW combi comes with 3 years more warranty.
- Hot water output: the Baxi 600 Combi 2 30kW has 6kW more hot water output.
- Central heating output: the Worcester Bosch Greenstar 4000 25kW combi puts out 4kW more to the radiators.
- Hot water flow rate: the Baxi 600 Combi 2 30kW runs 1.7 litres a minute more hot water.
- Seasonal efficiency: the Worcester Bosch Greenstar 4000 25kW combi is 1 points more efficient.
Specifications side by side
| Baxi 600 Combi 2 30kW | Worcester Bosch Greenstar 4000 25kW combi | |
|---|---|---|
| Hot water output | 30.9 kW | 25 kW |
| Central heating output | 21.2 kW | 25 kW |
| ErP class | A | A |
| Seasonal efficiency | 93% | 94% |
| Dimensions | 700 x 395 x 297 mm | 710 x 400 x 310 mm |
| Warranty | 7 years | 10 years |
| Hot water flow rate | 12.2 litres per minute | 10.5 litres per minute |
| Weight | - | 32.0 kg |
Sources: Baxi 600 Combi 2 30kW, 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 600 Combi 2 30kW if...
- you want one that has 6kW more hot water output
- you want one that runs 1.7 litres a minute more hot water
A gas combi boiler with 30.9 kW of hot water output, sized for a three-bed house with one or two bathrooms. It delivers about 12.2 litres per minute of hot water, which decides how well a shower runs while a tap is on. Warranty: 7 years. Seasonal efficiency is 93%.
Full 600 Combi 2 30kW specifications →Buy or hire the Greenstar 4000 25kW combi if...
- you want one that comes with 3 years more warranty
- you want one that puts out 4kW more to the radiators
- you want one that is 1 points more efficient
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 Baxi 600 Combi 2 30kW and the Worcester Bosch Greenstar 4000 25kW combi?
The Worcester Bosch Greenstar 4000 25kW combi comes with 3 years more warranty and puts out 4kW more to the radiators. The Baxi 600 Combi 2 30kW has 6kW more hot water output and runs 1.7 litres a minute more hot water. The Baxi 600 Combi 2 30kW is a gas combi boiler, 30.9 kW hot water output; the Worcester Bosch Greenstar 4000 25kW combi is a gas combi boiler, 25 kW hot water output.
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