Head to head
NIBE S2125 Model 8 vs Viessmann Vitodens 100-W 35kW combi
The NIBE S2125 Model 8 is a air/water heat pump, up to 5.4 kw heat output. The Viessmann Vitodens 100-W 35kW combi is a gas combi boiler, 34.9 kw hot water output.
Last reviewed 13 September 2026
Specifications side by side
| NIBE S2125 Model 8 | Viessmann Vitodens 100-W 35kW combi | |
|---|---|---|
| Dimensions | 1070 x 1130 x 820 mm (H x W x D) | 700 x 400 x 360 mm |
| Weight | 150 kg | 35 kg |
| Heat output | 5.33 kW (average climate), 5.4 kW (cold climate) | - |
| SCOP | 5.0 at 35C, 3.7 at 55C (average climate); 4.1 at 35C, 3.2 at 55C (cold climate) | - |
| Sound power | 49 dB(A) at nominal rating (EN12102) | - |
| Max flow temperature | up to 75C | - |
| Hot water output | - | 34.9 kW |
| Central heating output | - | 32 kW |
| ErP class | - | A |
| Seasonal efficiency | - | 98% |
| Warranty | - | 5 years |
| Hot water flow rate | - | 17 litres per minute |
Sources: NIBE S2125 Model 8, 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 S2125 Model 8 if...
A smaller NIBE S2125 rated to keep working in cold climates, reaching up to 65C flow even at -25C outdoors. It suits a smaller house where cold-weather reliability matters more than raw output.
Full S2125 Model 8 specifications →Buy or hire the Vitodens 100-W 35kW combi if...
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 NIBE S2125 Model 8 and the Viessmann Vitodens 100-W 35kW combi?
The NIBE S2125 Model 8 is a air/water heat pump, up to 5.4 kW heat output; the Viessmann Vitodens 100-W 35kW combi is a gas combi boiler, 34.9 kW hot water output.
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