Head to head
Baxi 800 Combi 2 36kW vs NIBE S2125 Model 12
The Baxi 800 Combi 2 36kW is a gas combi boiler, 36 kw hot water output. The NIBE S2125 Model 12 is a air/water heat pump, up to 8.4 kw heat output.
Last reviewed 13 September 2026
Specifications side by side
| Baxi 800 Combi 2 36kW | NIBE S2125 Model 12 | |
|---|---|---|
| Dimensions | 700 x 390 x 285 mm | 1070 x 1130 x 820 mm (H x W x D) |
| Weight | 29.5 kg | 160 kg |
| Hot water output | 36 kW | - |
| Central heating output | 26.4 kW | - |
| ErP class | A | - |
| Seasonal efficiency | 93% | - |
| Warranty | 10 years | - |
| Hot water flow rate | 15 litres per minute | - |
| Heat output | - | 6.80-7.60 kW (average climate), 8.4 kW (cold climate) |
| SCOP | - | 5.0 at 35C, 3.8 at 55C (average climate); 4.2 at 35C, 3.4 at 55C (cold climate) |
| Sound power | - | 49 dB(A) at nominal rating (EN12102) |
| Max flow temperature | - | up to 75C |
Sources: Baxi 800 Combi 2 36kW, NIBE S2125 Model 12. Figures vary by model year and options, so check with the supplier before you commit.
Buy or hire the 800 Combi 2 36kW if...
A gas combi boiler with 36 kW of hot water output, sized for a larger house with two bathrooms. It delivers about 15 litres per minute of hot water, which decides how well a shower runs while a tap is on. Warranty: 10 years. Seasonal efficiency is 93%.
Full 800 Combi 2 36kW specifications →Buy or hire the S2125 Model 12 if...
The larger NIBE S2125, sized for a medium house and rated to hold output down to -25C outdoor temperature. It shares its cabinet size with the smaller model but weighs 10 kg more for the larger compressor.
Full S2125 Model 12 specifications →Common questions
What is the difference between the Baxi 800 Combi 2 36kW and the NIBE S2125 Model 12?
The Baxi 800 Combi 2 36kW is a gas combi boiler, 36 kW hot water output; the NIBE S2125 Model 12 is a air/water heat pump, up to 8.4 kW heat output.
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