Head to head
Glow-worm Energy Combi 30C 30kW vs Vaillant ecoTEC plus 835 35kW combi
The Vaillant ecoTEC plus 835 35kW combi comes with 3 years more warranty and puts out 8kW more to the radiators.
Last reviewed 13 September 2026
Key differences
- Warranty: the Vaillant ecoTEC plus 835 35kW combi comes with 3 years more warranty.
- Central heating output: the Vaillant ecoTEC plus 835 35kW combi puts out 8kW more to the radiators.
- Hot water flow rate: the Vaillant ecoTEC plus 835 35kW combi runs 1.8 litres a minute more hot water.
- Hot water output: the Vaillant ecoTEC plus 835 35kW combi has 4kW more hot water output.
Specifications side by side
| Glow-worm Energy Combi 30C 30kW | Vaillant ecoTEC plus 835 35kW combi | |
|---|---|---|
| Hot water output | 30.6 kW | 35 kW |
| Central heating output | 25 kW | 32.8 kW |
| ErP class | A | A |
| Seasonal efficiency | 94% | 94% |
| Dimensions | 700 x 390 x 280 mm | 720 x 440 x 372 mm |
| Warranty | 7 years | 10 years with Vaillant Advance Boiler Protection Kit |
| Hot water flow rate | 12.5 litres per minute | 14.3 litres per minute |
| Weight | 33 kg | - |
Sources: Glow-worm Energy Combi 30C 30kW, Vaillant ecoTEC plus 835 35kW combi. Figures vary by model year and options, so check with the supplier before you commit.
Buy or hire the Energy Combi 30C 30kW if...
A gas combi boiler with 30.6 kW of hot water output, sized for a three-bed house with one or two bathrooms. It delivers about 12.5 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 30C 30kW specifications →Buy or hire the ecoTEC plus 835 35kW combi if...
- you want one that comes with 3 years more warranty
- you want one that puts out 8kW more to the radiators
- you want one that runs 1.8 litres a minute more hot water
- you want one that has 4kW more hot water output
A gas combi boiler with 35 kW of hot water output, sized for a larger house with two bathrooms. It delivers about 14.3 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 835 35kW combi specifications →Common questions
What is the difference between the Glow-worm Energy Combi 30C 30kW and the Vaillant ecoTEC plus 835 35kW combi?
The Vaillant ecoTEC plus 835 35kW combi comes with 3 years more warranty and puts out 8kW more to the radiators. The Glow-worm Energy Combi 30C 30kW is a gas combi boiler, 30.6 kW hot water output; the Vaillant ecoTEC plus 835 35kW combi is a gas combi boiler, 35 kW hot water output.
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