Head to head
Vaillant ecoTEC plus 825 25kW combi vs Worcester Bosch Greenstar 5800i AW 5kW
The Vaillant ecoTEC plus 825 25kW combi is a gas combi boiler, 25.4 kw hot water output. The Worcester Bosch Greenstar 5800i AW 5kW is a r290 monobloc air source heat pump, 6.80 kw heat output.
Last reviewed 13 September 2026
Specifications side by side
| Vaillant ecoTEC plus 825 25kW combi | Worcester Bosch Greenstar 5800i AW 5kW | |
|---|---|---|
| Dimensions | 720 x 440 x 338 mm | 800 x 1100 x 540 mm (H x W x D) |
| Weight | 36 kg | 143 kg |
| Hot water output | 25.4 kW | - |
| Central heating output | 20.8 kW | - |
| ErP class | A | - |
| Seasonal efficiency | 94% | - |
| Warranty | 10 years with Vaillant Advance Boiler Protection Kit | - |
| Hot water flow rate | 10.5 litres per minute | - |
| Heat output | - | 6.80 kW at 7/35C |
| SCOP | - | 4.53 (MCS, 35C flow) |
| Refrigerant | - | R290 (propane) |
| Sound pressure | - | 42 dB(A) |
| Max flow temperature | - | 75C |
Sources: Vaillant ecoTEC plus 825 25kW combi, Worcester Bosch Greenstar 5800i AW 5kW. Figures vary by model year and options, so check with the supplier before you commit.
Buy or hire the ecoTEC plus 825 25kW combi if...
A gas combi boiler with 25.4 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 with Vaillant Advance Boiler Protection Kit. Seasonal efficiency is 94%.
Full ecoTEC plus 825 25kW combi specifications →Buy or hire the Greenstar 5800i AW 5kW if...
Worcester Bosch's entry-size 5800i AW, using the natural refrigerant R290 and reaching a 75C flow temperature for existing radiator systems. It is marketed as one of the quieter units in this size at 42 dB(A) sound pressure.
Full Greenstar 5800i AW 5kW specifications →Common questions
What is the difference between the Vaillant ecoTEC plus 825 25kW combi and the Worcester Bosch Greenstar 5800i AW 5kW?
The Vaillant ecoTEC plus 825 25kW combi is a gas combi boiler, 25.4 kW hot water output; the Worcester Bosch Greenstar 5800i AW 5kW is a r290 monobloc air source heat pump, 6.80 kW heat output.
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