Head to head
NIBE S2125 Model 8 vs Vaillant ecoTEC plus 825 25kW combi
The NIBE S2125 Model 8 is a air/water heat pump, up to 5.4 kw heat output. The Vaillant ecoTEC plus 825 25kW combi is a gas combi boiler, 25.4 kw hot water output.
Last reviewed 13 September 2026
Specifications side by side
| NIBE S2125 Model 8 | Vaillant ecoTEC plus 825 25kW combi | |
|---|---|---|
| Dimensions | 1070 x 1130 x 820 mm (H x W x D) | 720 x 440 x 338 mm |
| Weight | 150 kg | 36 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 | - | 25.4 kW |
| Central heating output | - | 20.8 kW |
| ErP class | - | A |
| Seasonal efficiency | - | 94% |
| Warranty | - | 10 years with Vaillant Advance Boiler Protection Kit |
| Hot water flow rate | - | 10.5 litres per minute |
Sources: NIBE S2125 Model 8, Vaillant ecoTEC plus 825 25kW 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 825 25kW combi if...
A gas combi boiler with 25.4 kW of hot water output, sized for a flat or small house with one bathroom. It delivers about 10.5 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 825 25kW combi specifications →Common questions
What is the difference between the NIBE S2125 Model 8 and the Vaillant ecoTEC plus 825 25kW combi?
The NIBE S2125 Model 8 is a air/water heat pump, up to 5.4 kW heat output; the Vaillant ecoTEC plus 825 25kW combi is a gas combi boiler, 25.4 kW hot water output.
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