Head to head
NIBE S2125 Model 8 vs Vaillant aroTHERM plus 5kW
The NIBE S2125 Model 8 is a air/water heat pump, up to 5.4 kw heat output. The Vaillant aroTHERM plus 5kW is a r290 monobloc air source heat pump, 5 kw heat output.
Last reviewed 13 September 2026
Specifications side by side
| NIBE S2125 Model 8 | Vaillant aroTHERM plus 5kW | |
|---|---|---|
| Heat output | 5.33 kW (average climate), 5.4 kW (cold climate) | 5 kW |
| SCOP | 5.0 at 35C, 3.7 at 55C (average climate); 4.1 at 35C, 3.2 at 55C (cold climate) | up to 5.03 |
| Sound power | 49 dB(A) at nominal rating (EN12102) | 53 dB(A) at A7/W35, 58 dB(A) at A7/W55 |
| Dimensions | 1070 x 1130 x 820 mm (H x W x D) | 965 x 1100 x 450 mm (H x W x D) |
| Weight | 150 kg | 128 kg (operating) |
| Max flow temperature | up to 75C | 75C |
| Refrigerant | - | R290 (propane), low GWP |
Sources: NIBE S2125 Model 8, Vaillant aroTHERM plus 5kW. 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 aroTHERM plus 5kW if...
The smallest aroTHERM plus, sized for a well-insulated flat or small house. It uses the natural refrigerant R290 rather than an F-gas, and reaches a 75C flow temperature, which helps it work with existing radiators on a retrofit job.
Full aroTHERM plus 5kW specifications →Common questions
What is the difference between the NIBE S2125 Model 8 and the Vaillant aroTHERM plus 5kW?
The NIBE S2125 Model 8 is a air/water heat pump, up to 5.4 kW heat output; the Vaillant aroTHERM plus 5kW is a r290 monobloc air source heat pump, 5 kW heat output.
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