Head to head
Vaillant ecoTEC Pro 24kW combi vs Viessmann Vitodens 100-W 35kW combi
The Viessmann Vitodens 100-W 35kW combi comes with 3 years more warranty and runs 7.4 litres a minute more hot water.
Last reviewed 13 September 2026
Key differences
- Warranty: the Viessmann Vitodens 100-W 35kW combi comes with 3 years more warranty.
- Hot water flow rate: the Viessmann Vitodens 100-W 35kW combi runs 7.4 litres a minute more hot water.
- Hot water output: the Viessmann Vitodens 100-W 35kW combi has 12kW more hot water output.
- Central heating output: the Viessmann Vitodens 100-W 35kW combi puts out 7kW more to the radiators.
- Seasonal efficiency: the Viessmann Vitodens 100-W 35kW combi is 5 points more efficient.
Specifications side by side
| Vaillant ecoTEC Pro 24kW combi | Viessmann Vitodens 100-W 35kW combi | |
|---|---|---|
| Hot water output | 23.4 kW | 34.9 kW |
| Central heating output | 24.8 kW | 32 kW |
| ErP class | A | A |
| Seasonal efficiency | 93% | 98% |
| Dimensions | 720 x 440 x 338 mm | 700 x 400 x 360 mm |
| Weight | 38 kg | 35 kg |
| Warranty | 2 years standard, 7 years with Vaillant Advance registration | 5 years |
| Hot water flow rate | 9.6 litres per minute | 17 litres per minute |
Sources: Vaillant ecoTEC Pro 24kW combi, Viessmann Vitodens 100-W 35kW combi. Figures vary by model year and options, so check with the supplier before you commit.
Buy or hire the ecoTEC Pro 24kW combi if...
A gas combi boiler with 23.4 kW of hot water output, sized for a flat or small house with one bathroom. It delivers about 9.6 litres per minute of hot water, which decides how well a shower runs while a tap is on. Warranty: 2 years standard, 7 years with Vaillant Advance registration. Seasonal efficiency is 93%.
Full ecoTEC Pro 24kW combi specifications →Buy or hire the Vitodens 100-W 35kW combi if...
- you want one that comes with 3 years more warranty
- you want one that runs 7.4 litres a minute more hot water
- you want one that has 12kW more hot water output
- you want one that puts out 7kW more to the radiators
- you want one that is 5 points more efficient
A gas combi boiler with 34.9 kW of hot water output, sized for a larger house with two bathrooms. It delivers about 17 litres per minute of hot water, which decides how well a shower runs while a tap is on. Warranty: 5 years. Seasonal efficiency is 98%.
Full Vitodens 100-W 35kW combi specifications →Common questions
What is the difference between the Vaillant ecoTEC Pro 24kW combi and the Viessmann Vitodens 100-W 35kW combi?
The Viessmann Vitodens 100-W 35kW combi comes with 3 years more warranty and runs 7.4 litres a minute more hot water. The Vaillant ecoTEC Pro 24kW combi is a gas combi boiler, 23.4 kW hot water output; the Viessmann Vitodens 100-W 35kW combi is a gas combi boiler, 34.9 kW hot water output.
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