Plug-in solar: what all the fuss is about.

This route exists for everyone the rooftop route was never built for. Renters – the kit is yours and moves with you, landlord's nod needed for fixings. Flats with a decent-sized balcony – freestanding frames today, hanging kits and clearer planning rules still to come. Listed buildings and conservation areas, where roof panels mean a planning saga but a kit leaning in the garden usually doesn't. Homes with a north-facing roof and a south-facing fence. And anyone with £500 to £900 to hand but no appetite for £6,500. If rooftop solar's economics were a members' club, this is the door being propped open.

The law allows up to 2,000W of panels feeding an inverter capped at 800W. In actual objects: a standard panel is about 450W and roughly the size of a door lying on its side – 1.7 metres by 1.1. So a legal kit is one to four panels; the first certified kits are one-panel and two-panel affairs. Picture a door or two leaning against the fence at an angle, or standing on frames on the patio, with a lead running to an outdoor socket. The 800W cap is the whole design: small enough to be safe on an ordinary circuit, big enough to run the fridge, the router, the laptops and the general daytime hum of a house.

Germany's word for these is Balkonkraftwerk – balcony power plant – so you'd be forgiven for planning exactly that. Hold on. The government's own impact assessment says planning permission for balcony and wall mounting is 'uncertain': fixed panels only count as permitted development if they stick out less than 20cm, which means hanging them nearly vertical and losing a chunk of the output. The first certified kits are ground-mount only – UKSOL's carry an actual 'not suitable for balconies' label, and at 25kg a panel you can see their point. So day one in Britain is gardens, fences, patios and shed roofs. Hanging kits and clearer planning rules should follow – but if the balcony is your only option, this route says 'not quite yet' rather than 'yes'. Worth knowing how the Germans actually do it, though: panel hung on the balcony rail, flat lead through the window seal, plugged into an ordinary indoor socket – millions of them, entirely unremarkable. Britain's rules may well relax in that direction once the market beds in. They just haven't yet, and this page deals in 'is', not 'ought'.

The kit feeds whatever's switched on. Kettle boiling? The kit chips in. Nothing much on? The surplus doesn't vanish – it flows out through your meter into the street's wires, where it becomes the cheapest electricity your neighbours never knew they were getting. Physically it's exported; financially you're not paid – export payment schemes require certification these kits don't carry, though the government says it's exploring changing that. So yes: your spare units genuinely make the neighbourhood a touch greener, free of charge, with no paperwork and no thanks. Which is why the whole game is using the power yourself while the sun's out – and why our quiz asks who's home in the day.

The government's own modelling says a south-facing tilted kit generates around 690kWh a year and saves roughly £110; a vertical balcony-rail mounting is nearer £70. Our engine – built independently from the same primary sources – computes £112 for the same case, which is the kind of agreement we like. The Energy Saving Trust's independent modelling lands in the same postcode: £69 a year if you're out all day, £97 if you're home – their occupancy split, incidentally, being exactly the lever our checker asks you about. You'll see higher numbers in the press and lower ones from sceptics (some analysts assume less of the output gets used and land at £40–85). The truthful summary: a modest, real saving that depends almost entirely on whether someone's home in daylight to use the power.

£500 is the government's estimate of what kits will cost once this market reaches scale, and it's the number our engine models. The first certified kits have landed above that – £849 at launch, in limited stock – which is what day one of a new market looks like. For where it goes next, look at Germany: at volume, supermarket kits sell there from around €199, with Lidl shifting them off the shelf next to the bratwurst. Legal now – but certified stock, retail range and price discovery all need to come good over the next few months. If you're not in a hurry, waiting a quarter will likely be rewarded.

• –One kit per household, capped at 800W of inverter output (up to 2,000W of panel behind it).
• –It must have a factory-fitted UK plug, into an outdoor socket (IP55-rated or better). Extension leads, adapters, and cables trailed through windows are all out here – if you don't have an outdoor socket, an electrician can fit one for a modest sum. (Germany runs millions of these through flat window leads; Britain's spec may loosen that way in time, but today it's outdoor socket or nothing.)
• –No batteries in the kit – battery systems are excluded from this law (expected to follow later; Octopus has signalled plug-in batteries for 2027).
• –One notification form to your electricity network operator within 28 days. A form, not a fee.
• –No export payments: without an MCS certificate there's no smart export guarantee, so anything you don't use is given away.
• –Renters: you'll need the landlord's nod for fixings – but the kit is yours and moves with you.
• –Already have rooftop solar? Adding a kit can push your home over the simple-connection limit and trigger a formal application to your network operator first – a process, not a purchase.

The government has earmarked up to £25m of Warm Homes Plan money for plug-in solar – but read the small print before celebrating: it's a pilot delivered through councils and metro mayors, aimed at low-income households street by street. There is no application form, and no scheme design has even been published yet. What you CAN access today: the Warm Homes Local Grant through your council if you're on a lower income, ECO4 until December 2026, and low-interest solar loans arriving from 2027. For the flavour of where the pilot is headed, the government filmed a London street taking control of its own energy supply – it's in the watch list below.

Germany is the existence proof: about 1.3 million registered plug-in systems, supermarket price wars, and a boring, functioning market. The Netherlands is the counter-example – its wiring standard requires a dedicated circuit, its cabinet declined to promote plug-in solar as recently as July 2026, and adoption is near zero. Flanders, meanwhile, legalised plug-in solar and batteries together in 2025. Britain has chosen the German road with British paperwork. One warning for your reading: the '400,000 kits in France' figure that circulates online is unsourced – the French industry's own barometer marks that market 'not measured'. We don't use it, and nor should anyone else.

Five electrical safety bodies issued a joint statement in June urging caution, and Electrical Safety First advises buying from reputable high-street retailers rather than marketplace listings – advice we'd underline twice. Two engineering notes worth the candle: the law doesn't require an electrician, but the safety bodies recommend a wiring check (upwards of £150) for older homes before plugging in – British sockets have spent their whole lives sending power one way, and this is the first product to send it back. And ask your electrician whether your RCDs – the trip switches in the fuse box – are bidirectional; older ones aren't designed for reverse flow. Belt, braces, and a quieter conscience. Marketplace 'energy-saving' plug scams are a documented problem, and non-compliant overseas kits will not vanish from listings on 27 August. The boring, correct routine: check the register, buy a certified kit from a real retailer, plug it into its own socket (never an extension lead), and send the network operator form. That's the whole ritual.