NIBE vs Grant heat pumps: sizes, SCOP, noise and guarantee

Quick answer: Grant wins on range and price. The Aerona 290 comes in five sizes from 4kW to 15.5kW, publishes 48 to 53.6 dB(A) sound power, and the 9kW listed at £2,689.40 ex VAT in July 2026. NIBE’s S2125 only comes in 8 and 12kW, which rules it out of a lot of British houses.

We haven’t tested these units. This comes from the Grant UK Aerona 290 installation manual (DOC 0204 Rev 1.8, April 2026), NIBE’s S2125 specification sheet and UK trade listings, all checked on 28 July 2026.

Two propane monoblocs with very different ambitions

NIBE is a Swedish manufacturer selling a system. The S2125 is designed to pair with a NIBE S-series indoor module, and the controls, the app and the hot water cylinder are all part of the same design. Buy into it and you get a coherent piece of engineering.

Grant is an Irish family firm that spent thirty years selling oil boilers into rural Britain and then pivoted hard to heat pumps. The Aerona range is built for the installer who already fits Grant kit, and the Aerona 290 is the propane replacement for the R32 Aerona3. It’s less elegant. It’s also cheaper, comes in more sizes and carries a longer guarantee.

The published numbers

Sizing is where NIBE loses this

A decently insulated three-bed semi in the North West usually lands somewhere between 5 and 7kW of design heat loss. NIBE’s smallest S2125 is 8kW.

Fit an 8kW machine to a 5kW house and it spends most of the heating season trying to turn itself down below its minimum modulation, then cycling on and off instead. That’s short cycling. It wears the compressor and quietly costs you efficiency you’ve already paid for. Grant’s 4kW and 6.5kW models exist precisely to avoid it, and the 6.5kW posts the highest SCOP in either range at 5.08.

If your heat loss survey comes back above 8kW, the objection disappears and NIBE is competitive again. Get the survey done properly first. Our guide to sizing a heat pump for UK properties explains what a real calculation looks like, and why the installer who sizes off floor area is guessing.

Noise: closer than the headlines suggest

NIBE quotes a single sound power figure of 49 dB(A) for both S2125 sizes, measured to EN 12102 at 7/45. Grant publishes a figure per model, from 48.0 dB(A) on the 4kW to 53.6 dB(A) on the 9kW, plus sound pressure at both 1 and 3 metres.

So the small Grant is marginally quieter than the NIBE and the mid-range Grants are marginally louder. Nothing here is decisive. What is useful is that Grant gives your installer the 3-metre sound pressure figures directly, which makes the MCS 020 calculation quicker to sanity-check. Since 29 May 2025, permitted development in England has required the MCS 020 a) version, which has to show 37 dB or less at 1 metre from the window or door of a neighbour’s habitable room; it replaced the old calculation’s 42 dB(A) figure, which included background noise. More on that in our planning and noise guide.

The coastal clause nobody mentions

NIBE’s 7-year warranty terms require Blygold protective coating on units installed within one kilometre of the shore. If you live in Blackpool, Lytham, Cleveleys or Morecambe, that’s an extra cost and an extra thing your installer has to specify correctly, and getting it wrong voids the cover.

NIBE’s baseline is also thin: 24 months parts and labour, or 33 months from date of manufacture, whichever ends first. The 7 years only comes through a NIBE Pro Partner or Pro Exclusive installer, registered within 28 days, with annual servicing and Benchmark paperwork. Grant’s 7 years runs through its G1 installer scheme on similar conditions.

Price

The Grant Aerona 290 9kW listed at £3,227.28 including VAT (£2,689.40 ex) at Pirate Heating Supplies on 28 July 2026. We couldn’t find a comparable single-unit UK retail price for the S2125, which usually sells as part of a package with a NIBE indoor module rather than as a standalone box. Treat that as a signal about how each brand goes to market.

Fitted, our modelled UK average for a heat pump installation is £11,014 before the £7,500 Boiler Upgrade Scheme grant. See how we calculate costs for the method, or run your own numbers in the calculator.

The verdict

Grant Aerona 290, for most British houses. Five sizes means you can actually match the machine to the heat loss, the 4kW is one of the quietest units on the market at 48 dB(A), and the price is roughly a third below the premium German brands. And the efficiency is within a whisker of NIBE’s at every comparable point.

NIBE S2125 if your heat loss is genuinely 8kW or more, you want the S-series controls and indoor module as one designed system, and you’re not near the coast. NIBE is also the only brand here that publishes cold-climate SCOPs, which tells you something about how confident it is at low ambient temperatures. For the rest of the field, see our brand comparison.

FAQs

Is Grant a budget brand?

It’s cheaper, but the Aerona 290 posts SCOPs of 4.56 to 5.08 at 35°C, which is at the top of the market. The cost saving comes from a simpler product and a UK-focused distribution model rather than from weaker engineering.

Does the NIBE S2125 work without a NIBE indoor module?

It can be paired with third-party hydraulics, but you lose the integrated controls that are much of the reason to buy NIBE. Most UK installers quote it as a package with a VVM or SMO indoor unit.

Which is better for a house with old radiators?

Both reach 75°C. NIBE’s 12kW posts the better 55°C SCOP at 3.80, against 3.74 for Grant’s 12kW, so they’re effectively level. Radiator sizing will change your bills far more than the choice between these two units.