A heat pump you can fit in a weekend? 2025’s new compact model

The average air-source heat pump weighs 120kg and needs a concrete plinth, a dedicated 32A circuit, and two days of work by a certified engineer. That is a lot of friction for a homeowner who just wants a lower gas bill. Next year, a Swedish manufacturer is trying to change that.

NIBE, one of Europe’s largest heat-pump makers, will launch the S2125 in the UK in 2025, a unit it claims can be installed in a single day by two people, with no groundworks required. The news was first reported by The Eco Experts. The machine is 40% smaller and 30% lighter than a standard model, at roughly the size of a small washing machine. That matters for the thousands of UK homes where a conventional heat pump simply does not fit, terraced houses with no side passage, flats with a balcony, or homes where the back garden is a patio the size of a pool table.

Who qualifies, and who doesn’t

The S2125 is a monobloc air-source heat pump, meaning the entire refrigerant circuit is sealed in the outdoor unit. That removes the need for a separate indoor cylinder in some configurations, though most homes will still need a hot-water tank unless they already have a compatible system. The unit delivers 5 kW of heating, enough for a well-insulated 3-bed semi with a heat loss below 4 kW. For a typical 1930s semi with single glazing and no cavity-wall insulation, that figure is often 8-10 kW, the S2125 would struggle to keep up on a January evening.

Eligibility for the Boiler Upgrade Scheme (BUS) remains unchanged: homeowners in England and Wales can claim £7,500 off the installed cost, provided they use an MCS-certified installer. The S2125 is not a DIY device; the installer still handles the electrical connection, refrigerant charge, and commissioning. The ‘easy install’ claim refers to the physical handling and mounting, not the legal paperwork.

What it costs a typical 3-bed semi

NIBE has not published a UK retail price, but a standard 5 kW monobloc heat pump currently costs between £2,500 and £4,000 for the unit alone. The S2125 is likely to be in a similar bracket, perhaps £3,000-£3,500. The real saving is in labour: a conventional installation runs £3,000-£5,000 for a two-day job with two engineers. If the S2125 cuts that to one day with two people, labour could fall to £1,500-£2,500. Total installed cost after the BUS grant could therefore land around £2,000-£4,000, comparable to a gas boiler replacement, which typically runs £2,500-£4,000.

But the catch is that the S2125’s efficiency depends heavily on the heating system it connects to. It works best with underfloor heating or large radiators designed for low flow temperatures (35-45°C). Most UK homes still have radiators sized for 60-70°C flow from a gas boiler. Retrofitting larger radiators or installing underfloor heating adds £2,000-£6,000 to the total cost, a figure the marketing material tends to leave out.

Does it fix the installer shortage?

The UK needs 50,000 trained heat-pump installers by 2030 to meet the government’s target of 600,000 installations a year. Currently, there are fewer than 5,000. A lighter, simpler unit might reduce the training burden: a gas boiler engineer with no heat-pump experience could plausibly learn to install the S2125 in a few days, rather than the weeks required for conventional models. The Department for Energy Security and Net Zero has not commented on whether the S2125 qualifies for any fast-track certification, but NIBE has confirmed it will work with existing MCS-accredited installers initially.

What this misses is the bigger bottleneck: the electrical grid. A 5 kW heat pump draws about 21 amps at 240V. Many older homes have a 60A or 80A main fuse and a consumer unit that cannot take another dedicated circuit without an upgrade. An electrician’s visit for a fuse upgrade and new circuit costs £500-£1,000. That is not included in the installer’s quote, and the BUS grant does not cover it.

Households on standard variable tariffs can start researching now, but the S2125 will not be available to order until Q2 2025. In the meantime, the best action is to get a heat-loss survey from an MCS-certified installer (cost typically £150-£300) and check whether your home’s insulation and radiator sizing can support a low-temperature heat pump. If the answer is yes, the S2125 might be the easiest path to a lower gas bill, and a better EPC rating, that this market has yet seen.