Head to head
Glow-worm Energy Combi 25C 25kW vs Viessmann Vitocal 150-A13
The Glow-worm Energy Combi 25C 25kW is a gas combi boiler, 25.7 kw hot water output. The Viessmann Vitocal 150-A13 is a r290 air source heat pump, 8.1 kw heat output.
Last reviewed 13 September 2026
Specifications side by side
| Glow-worm Energy Combi 25C 25kW | Viessmann Vitocal 150-A13 | |
|---|---|---|
| Dimensions | 700 x 390 x 280 mm | 920 x 450 x 360 mm (H x W x D) (indoor unit); 841 x 1144 x 600 mm (H x W x D, single fan) (outdoor unit) |
| Weight | 32 kg | 162 kg (single fan) (outdoor unit) |
| Hot water output | 25.7 kW | - |
| Central heating output | 18 kW | - |
| ErP class | A | - |
| Seasonal efficiency | 94% | - |
| Warranty | 7 years | - |
| Hot water flow rate | 10.4 litres per minute | - |
| Heat output | - | 8.1 kW at A7/W35 |
| COP | - | 4.7-5.0 at A7/W35 |
| Refrigerant | - | R290 (propane), GWP 0.02 |
| Sound power | - | 51 dB(A) assessed total at A7/W55 |
| Max flow temperature | - | 70C down to -10C outdoor |
Sources: Glow-worm Energy Combi 25C 25kW, Viessmann Vitocal 150-A13. Figures vary by model year and options, so check with the supplier before you commit.
Buy or hire the Energy Combi 25C 25kW if...
A gas combi boiler with 25.7 kW of hot water output, sized for a flat or small house with one bathroom. It delivers about 10.4 litres per minute of hot water, which decides how well a shower runs while a tap is on. Warranty: 7 years. Seasonal efficiency is 94%.
Full Energy Combi 25C 25kW specifications →Buy or hire the Vitocal 150-A13 if...
A Vitocal 150-A monobloc-style split heat pump using the natural refrigerant R290, rated at 8.1kW and reaching a 70C flow for boiler-replacement work. Viessmann-trained installers can extend the standard warranty on registration.
Full Vitocal 150-A13 specifications →Common questions
What is the difference between the Glow-worm Energy Combi 25C 25kW and the Viessmann Vitocal 150-A13?
The Glow-worm Energy Combi 25C 25kW is a gas combi boiler, 25.7 kW hot water output; the Viessmann Vitocal 150-A13 is a r290 air source heat pump, 8.1 kW heat output.
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