Plug-in solar panels hit UK supermarkets at £500 but caveats loom

Retail giants are stacking plug-in solar panels on shelves for £500, the cheapest route yet to generating your own electricity. But this is not the solar revolution it first appears.

As reported by The Independent, Tesco, Sainsbury’s and others will stock these kits from this autumn. For a typical 3-bed semi using 3,500 kWh a year, the saving could be £80–£100 annually, roughly a 20–25% cut on the electricity portion of a bill now capped at £1,928. That is real money. But the fine print matters more than the price tag.

Who qualifies, and who doesn’t

Plug-in panels plug into a standard wall socket via a microinverter. No electrician, no scaffolding, no roof work. That is the appeal. But they are limited to around 350–400 watts per panel, about a quarter of a typical rooftop panel. To match a 3.5 kW rooftop array you would need nine of these at a cost of £4,500, which is more than a professionally installed 4 kW system from a certified installer (typically £5,000–£6,000 after VAT cut). The catch: you cannot daisy-chain them without exceeding the 16-amp limit of a domestic ring main, and most houses have only one or two external sockets. The Energy Saving Trust recommends a maximum of two panels per circuit to avoid tripping breakers.

But there is a deeper issue. These panels do not count toward your EPC rating. The government’s Standard Assessment Procedure (SAP) only recognises PV systems that are fixed to the building fabric and registered with a competent person scheme. A plug-in panel, however efficient, cannot lift your EPC from D to C. That matters if you are selling or remortgaging.

What it costs a typical 3-bed semi

At £500 per panel, a single unit will generate about 250–300 kWh a year in the south of England. At the current price cap of 27p per kWh, that saves £68–£81. Payback is six to seven years, not bad for a plug-in appliance. But the panel’s lifespan is typically 10–12 years, so total lifetime saving is around £700–£900. Compare that with a rooftop system: £5,500 for a 4 kW array, saving £500–£600 a year, paying back in 9–11 years but lasting 25+ years. The plug-in is cheaper upfront, less efficient per pound, and needs replacing sooner.

The Office for Product Safety and Standards has flagged fire risks from poorly installed microinverters and trailing cables. The British Electrotechnical and Allied Manufacturers Association (BEAMA) recommends using only units with a G98 compliance certificate and notifying your Distribution Network Operator (DNO) via your energy supplier. Most supermarkets do not include this in the box.

What this misses, and what to do instead

Yet the biggest blind spot is the Smart Export Guarantee (SEG). To be paid for surplus electricity exported to the grid, your system must be installed by an MCS-certified installer. Plug-in panels, being self-installed, are not MCS-registered. You will get no export income, typically 5–15p per kWh, and you lose the 0% VAT rate that applies to professional installations until 2027. Your supermarket panel costs £500 inc. 20% VAT. A professional system of the same size would cost £416 after VAT relief.

For renters or flat dwellers with a balcony, a single plug-in panel makes sense: it offsets a phone charger, TV and laptop. For homeowners with a roof, the maths still favours a proper install. The catch is that supermarkets are selling hope in a box, and hope does not come with a G98 certificate.

Households considering a plug-in panel should check their home insurance policy first. Many providers require notification of any fixed electrical generation equipment. They should also confirm with their DNO that the local grid can accept a microgenerator, most can, but some urban substations are saturated. The panel itself is a start. But the real prize, lower bills, higher EPC, export income, still belongs to the rooftop system.