NIBE S2125 or F2120: the SCOP figures are not comparable
One is declared under EN 14825:2018 and the other under the 2013 edition, so the two SCOP numbers cannot be ranked. Supply temperature and phase can be.
What this means
NIBE declares the S2125 at SCOP 5.0 for average climate at 35 by 55 degrees under EN 14825:2018, and the F2120 at above 5.0 for average climate at low temperature under EN 14825:2013. Different editions and differently stated conditions mean the two cannot be ranked against each other. The comparable differences are a 75 degree supply temperature against 65, and a single-phase range against a mainly three-phase one.
Equipment and model context
NIBE S2125 and F2120 air-to-water heat pumps
- NIBE S2125-8 and S2125-12
- NIBE F2120-8 in 3x400 V and 1x230 V
- NIBE F2120-16 and F2120-20 in 3x400 V
Both ranges as NIBE publishes them for Europe and the United Kingdom. The S2125 declaration is stated to apply to the -8 and -12, and the F2120 declaration to the -16 and -20, so neither figure covers every size in its own range.
What this guide covers
- Two NIBE outdoor units on a shortlist with efficiency figures that appear to contradict the model ages.
- A property with a single-phase supply and a large heat loss.
- A retrofit that needs a supply temperature above 65 degrees.
What changes the answer
- Seasonal efficiency declarations are tied to an edition of EN 14825 and to a stated application.
- The two ranges sit on different electrical supplies and cover different output bands.
Why the two SCOP numbers cannot be put in one column
NIBE's S2125 specification sheet states SCOP of 5.0 for average climate and above 4.1 for cold climate, both at 35 by 55 degrees, in accordance with EN 14825:2018, and says the figures apply to the -8 and -12. The F2120 product page states SCOP above 5.0 for average climate and 4.3 for colder climate at low temperature, according to EN 14825:2013, applying to the -16 and -20.
Three things differ before any number is compared. The edition of the standard, the way the application is described, and which sizes in each range the declaration covers. A revision of a test standard changes the load bins and the assumptions behind them, which is exactly what a seasonal figure is made of.
The cold-climate figures make the trap visible. F2120 declares 4.3 and S2125 declares above 4.1, which reads as a win for the older unit until the edition is noticed. Neither number is wrong and neither is a ranking.
What is comparable, starting with supply temperature
The S2125 reaches a 75 degree Celsius supply temperature and holds up to 65 degrees at an outdoor temperature of minus 25. The F2120 reaches 65 degrees and holds up to 63 at minus 25.
Ten degrees at the top end is the difference between a range that can drive an unimproved radiator circuit and one that is designed for a lower-temperature system. At minus 25 the gap closes to two degrees, so the advantage is in the ceiling rather than in cold-weather behaviour.
For a retrofit where the emitter schedule cannot be finished before the heating season, the higher ceiling is the property that buys time. For a new build with underfloor heating, it is a capability that will never be used.
Electrical supply is the constraint that decides most projects
The S2125 is listed at 230 volts and 50 hertz, in sizes 8 and 12. NIBE describes the F2120 as having a three-phase connection which simplifies electrical installation, and lists variants as F2120-8 in both 3x400 V and 1x230 V, with the -16 and -20 in 3x400 V.
A domestic property in the United Kingdom with a single-phase supply and a heat loss above 12 kilowatts is therefore looking at the F2120-8 in its single-phase form and nothing larger, unless a supply upgrade is on the table.
That is not a preference, it is a gate. It is worth settling before efficiency figures are compared at all, because it removes most of the shortlist in a large single-phase property.
What the F-Gas note on the S2125 sheet means
The S2125 specification sheet carries a carbon dioxide equivalent of 0.0024 tonnes for the hermetically sealed refrigerant circuit, with a footnote saying the unit does not require annual inspection under the F-Gas Regulation.
The mechanism is that leak-check obligations under the regulation start at a charge threshold expressed in carbon dioxide equivalent, and a small charge of a low global warming potential refrigerant in a sealed circuit falls below it. The consequence for an owner is one fewer recurring appointment across the life of the system.
It is a statement about that model and that circuit rather than about heat pumps in general, and it does not remove the maintenance a manufacturer specifies for its own warranty.
| Property | S2125 | F2120 |
|---|---|---|
| Maximum supply temperature | 75 degrees Celsius | 65 degrees Celsius |
| Supply temperature at minus 25 outdoors | Up to 65 degrees | Up to 63 degrees |
| Sizes listed | 8 and 12 | 8, 16, and 20 |
| Electrical supply | 230 V, single phase | Mainly 3x400 V, 1x230 V on the -8 |
| SCOP declaration edition | EN 14825:2018 | EN 14825:2013 |
| Sizes the declaration covers | -8 and -12 | -16 and -20 |
| The property | Where it lands |
|---|---|
| Single-phase supply, load under 12 kilowatts | S2125 covers it in either size |
| Single-phase supply, load above 12 kilowatts | F2120-8 in 1x230 V, or a supply upgrade |
| Three-phase available, large load | F2120-16 or -20 |
| Retrofit needing above 65 degrees | S2125, on its 75 degree ceiling |
| New build at 35 degrees | The supply temperature ceiling is not in use |
| Comparing the two on SCOP | The declarations are on different standard editions |
Four attributes travel with every SCOP figure, and a comparison is only meaningful when all four match. Two NIBE sheets differ on three of them.
- Standard editionEN 14825:2018 against EN 14825:2013
- Climate profileAverage or cold, each with its own bins
- Application temperatureStated as 35 by 55, or as low temperature
- Sizes coveredThe declaration names which variants it applies to
Questions people ask about this
Is the NIBE F2120 more efficient than the S2125?
The published figures cannot answer that. The F2120 declaration is under EN 14825:2013 for the -16 and -20 at low temperature, and the S2125 declaration is under EN 14825:2018 for the -8 and -12 at 35 by 55 degrees. Different editions and applications are not a ranking.
Which NIBE heat pump reaches the highest flow temperature?
The S2125, at a supply temperature of up to 75 degrees Celsius. The F2120 reaches 65. At an outdoor temperature of minus 25 the two are much closer, at up to 65 and up to 63 degrees.
Does the NIBE F2120 need a three-phase supply?
NIBE describes the F2120 as having a three-phase connection and lists the -16 and -20 in 3x400 V. The F2120-8 is listed in both 3x400 V and 1x230 V, so single-phase is available at the smallest size only.
Does a NIBE S2125 need annual F-Gas inspection?
The specification sheet states that it does not, and gives a carbon dioxide equivalent of 0.0024 tonnes for the hermetically sealed circuit. Leak-check duties under the regulation begin above a charge threshold that this figure sits below.
How loud is the NIBE S2125?
The specification sheet gives a sound level LWA under EN 12102 at a 7 by 45 condition of 49 dB(A). That is a sound power figure at one operating condition rather than what is heard at a distance.
Evidence recordHow this page was checked
official manufacturer support article, operation manual · checked 2026-09-07
Every technical claim above was written from primary documentation held in the HVAC Bench evidence record: NIBE technical literature. Where a source limits a definition to certain models, test conditions, or product classes, that limit is repeated here rather than generalised.
- Documentation class
- official manufacturer support article, operation manual
- Scope of the definition
- NIBE S2125 and F2120 air-to-water heat pumps
- Last checked
- 2026-09-07