Kelvin One is a mobile split air conditioner with a plug-in solar pack. The hotter the day, the more of your cooling the sun covers. No drilling. No installer. No planning permission. Carry it home, hang the small half out of an open window, and be cool before the kettle boils.
£999 per room. The average installed system quote is £3,500 to £5,000, and you can't take that with you when you move.
Drag the heat up and watch the sun pick up the bill.
Ask why UK homes swelter and nobody says "I don't want to be cool." They say: I rent. I can't drill the wall. I don't want a box bolted to the house. I can't face the quotes, the waiting list, the two-day install. The barrier was never desire. It was commitment. Kelvin One removes the commitment.
Provisional June record, 2026, with Red Extreme Heat Warnings across England and Wales. The nights people remember are the ones they couldn't sleep.
UK homes with fixed air conditioning. Not because Britain is cool, but because the buying process asks too much of people.
Mobile split units sold out across Europe in the 2026 heatwaves. Proof that when you remove the installer, the demand was there all along.
Real split-system cooling, the kind that actually chills a whole room, with nothing fixed to your house. The quiet half lives in your room, the working half hangs outside an open window on a no-drill bracket, and a flat line thin enough to close the window on connects the two.
The compressor, the noisy part, lives outside the glass. What's in your room is a slim blade you can carry one-handed: 37dB in silent mode, quieter than a library, engineered for the lightest sleepers in the smallest terraces.
A 10kg outdoor unit, about the weight of a full shopping bag, sits on a tool-free bracket made for British casement and tilt-and-turn windows. When you move house, it moves with you. Renting is not a reason to be hot.
The two halves connect through a flat, sealed line slim enough that the window shuts snugly onto it with the seal kit. No fat elephant-trunk hose, no gale through the gap, and no negative pressure sucking warm air back in. That last one is the reason ordinary portables never quite work.
One plug-in solar pack feeds every Kelvin in the house, straight into the units' DC hearts, skipping the conversion losses of bolt-on panels. Peak sun and peak heat arrive together, so on the worst afternoons the sun carries most of the load. Poetic justice, plumbed in.
Whole-house air conditioning is a solution to a problem nobody has. You're only ever in one or two rooms. Kelvin Ones are bought per room and talk to each other: they run where you are, pre-chill the bedroom on free afternoon sun before you ever walk in, and take turns drawing power so four units never trouble a single 13-amp plug. Four dumb boxes is a purchase. Four coordinated ones is a system.
Every figure is an engineering target benchmarked against the category leader, and each one maps to something you'd actually feel: a silent bedroom, a smaller bill, a window that still closes.
| Type | Mobile split air conditioner + heat pump No planning permission |
| Cooling / heating | 3.5 kW cooling · 3.2 kW heating · one unit, both seasons |
| Efficiency | SEER ≥6.3 (A++) · SCOP ≥4.0 (A+) |
| Indoor noise | ≤37 dB(A) silent mode Quieter than a library |
| Refrigerant | R290, GWP 3 225× cleaner than R32 |
| Outdoor unit | ≤10 kg, tool-free UK window bracket |
| Connecting line | Flat ≤27 mm. The window closes onto it |
| Solar pack (shared) | 800W plug-in panels + 2 kWh battery, DC-direct |
| Install | Self-setup in minutes. No drill. No engineer. No mark left. |
| Power | Standard 13A plug · units coordinate to share the circuit |
| Target price | £999 per room · solar pack from £449, one per home |
Last summer proved that people want real air conditioning without the installer. Here's what the first generation still doesn't do, and what Kelvin One will.
During the 40°C heatwaves, units sold out across European retailers, chosen precisely because they need no installer, no drilling, and no permission. The idea works. Millions of people now know it works.
Every unit on the market today runs purely off the plug, even though its hardest-working hour is the sunniest hour of the year. Kelvin One feeds solar power straight into the unit's DC electronics, so the brightest afternoons are the cheapest ones.
Today's kits are built around continental windows and an R32 refrigerant with 225× the warming potential of ours. Kelvin One mounts on British casements and tilt-and-turns, and runs on R290 with a warming potential of just 3.
Buy one per room and today's units don't know each other exists. Kelvins do. They share the circuit politely, cool the rooms you're actually in, and pre-chill the bedroom on free afternoon sun before you ever walk in.
Start with the room that ruins your sleep. Add more when you're convinced. Nobody measures your walls, and nothing gets drilled into them.
No landlord permission, no drilling, no mark left when you move out. Kelvin One belongs to you, not the building. When you move, it comes with you like any other appliance you own.
There's a heat pump inside, so the same unit that cools your bedroom in a heatwave heats your home office in winter for a fraction of gas-boiler cost. It earns its place in every season, not six weeks a year.
Most people start with the bedroom. After the first properly cool night's sleep, the home office and living room tend to follow. Add the solar pack whenever you like; one pack feeds every Kelvin in the house.
The quiet acoustics, the flat window line, the clean R290 refrigerant, and the solar-fed electronics are all designed together, from scratch, for British homes and British weather. This is not a generic unit with a new badge on it.
The first 500 places get more than a launch email. Founders are first in line for the 50-home pilot, lock the £999 launch price before it rises, and get a say in what we build, starting with which window your house has.
Places are numbered. Yours is waiting.
Funds cover prototype engineering with a UK design partner and refrigeration specialists, certification, and a 50-home pilot in one English region, with real sleep, real bills, and real solar data as the output. Request the deck and financial model below.