Head to head
NIBE S2125 Model 8 vs Vaillant ecoTEC plus 835 35kW combi
The NIBE S2125 Model 8 is a air/water heat pump, up to 5.4 kw heat output. The Vaillant ecoTEC plus 835 35kW combi is a gas combi boiler, 35 kw hot water output.
Last reviewed 13 September 2026
Specifications side by side
| NIBE S2125 Model 8 | Vaillant ecoTEC plus 835 35kW combi | |
|---|---|---|
| Dimensions | 1070 x 1130 x 820 mm (H x W x D) | 720 x 440 x 372 mm |
| 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) | - |
| Weight | 150 kg | - |
| Max flow temperature | up to 75C | - |
| Hot water output | - | 35 kW |
| Central heating output | - | 32.8 kW |
| ErP class | - | A |
| Seasonal efficiency | - | 94% |
| Warranty | - | 10 years with Vaillant Advance Boiler Protection Kit |
| Hot water flow rate | - | 14.3 litres per minute |
Sources: NIBE S2125 Model 8, 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 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 ecoTEC plus 835 35kW combi if...
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 NIBE S2125 Model 8 and the Vaillant ecoTEC plus 835 35kW combi?
The NIBE S2125 Model 8 is a air/water heat pump, up to 5.4 kW heat output; the Vaillant ecoTEC plus 835 35kW combi is a gas combi boiler, 35 kW hot water output.
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