From next month, Tesco, Sainsbury’s and B&Q will stock plug-in solar panels for £500, a price that undercuts a full rooftop array by a factor of ten. The offer is aimed at the 80% of UK households who say they want solar but are put off by upfront cost, according to a 2024 survey by the Energy Saving Trust. But the small print, as reported by The Independent, reveals a product that promises much but delivers little to anyone serious about cutting bills or improving their Energy Performance Certificate.
What £500 actually buys
A typical plug-in panel produces 200 to 400 watts, enough to run a laptop, a television and a few LED bulbs on a sunny afternoon. That’s roughly 10% of the output from a standard 3.5kW rooftop system. At current electricity prices of around 25p per kWh, the panel saves about £30-£60 a year, assuming 900 hours of decent sunlight in the UK. Payback on the £500 purchase price therefore takes between eight and 17 years, longer than the product’s typical warranty. The catch is the low output. These panels plug into a standard three-pin socket via a microinverter, but Ofgem’s rules require any generator above 16 amps, about 3.6kW, to have a G98 or G99 certification and prior notification to the Distribution Network Operator. Most plug-in panels fall below that threshold, so they are technically legal, but only if the microinverter is certified. Many budget models are not, leaving the homeowner in a grey area that could invalidate their home insurance or breach their grid connection terms.
EPC impact, zero unless MCS-certified
Homeowners hoping to boost their EPC rating from D to C should look elsewhere. The government’s Standard Assessment Procedure, which underpins EPC calculations, only recognises solar panels installed by a Microgeneration Certification Scheme accredited installer. A DIY plug-in panel bought from a supermarket shelf does not qualify. The Energy Saving Trust confirms that without MCS certification, the panel cannot be included in the EPC report. That matters because a higher EPC rating can add 3-5% to a home’s value, according to Nationwide’s 2023 analysis. The £500 panel adds nothing to resale value, while a certified 3.5kW system typically adds £2,000-£4,000.
The Smart Export Guarantee, you don’t get it
Rooftop solar owners with an MCS-certified installation can sell surplus electricity back to the grid under the Smart Export Guarantee, earning roughly 5-15p per kWh depending on the supplier. Plug-in panels are excluded from SEG because they lack the required metering and certification. So any electricity you don’t use, during a sunny day when you’re out, is given away for free. Ofgem’s latest data shows the average SEG payment for a typical 3.5kW system is about £120 a year. That’s more than double the total annual saving from the plug-in panel. The gap widens further when you factor in the 20% VAT that applies to plug-in panels versus the 0% VAT on MCS-certified installations under the government’s current relief scheme.
Who should buy one, and who shouldn’t
The plug-in panel makes sense for a narrow group: flat dwellers with a balcony, tenants who cannot alter the roof, or households who want to power a single device like a shed or greenhouse. For anyone with a roof, a mortgage, and an ambition to cut bills by more than the price of a takeaway coffee each week, the £500 is better saved toward a full system. The typical 3.5kW array costs £5,000-£7,000 after the 0% VAT relief, earns SEG income, adds EPC points, and pays back in 8-12 years. The supermarket panel pays back in never, or in one sunny afternoon, depending on whether you count the moment you realise you’ve bought a gadget, not a solution.
What to do next
Households considering solar should get three quotes from MCS-certified installers through the Energy Saving Trust’s directory. The government’s Boiler Upgrade Scheme, which covers heat pumps, does not cover solar, but households earning under £31,000 may qualify for the Home Energy Scotland grant or the Great British Insulation Scheme. The next Ofgem price cap update in October 2025 will push electricity rates higher, making every kWh of self-generation more valuable. The £500 panel will still be there on the shelf. The question is whether you want a toy or a return on investment.
Frequently Asked Questions
No. A typical plug-in panel produces 200-400W, enough for a laptop and a few lights, but not for a kettle (2,000W), washing machine (1,500W), or fridge (150W continuous). To power a whole house you'd need a rooftop system of at least 3kW, costing £5,000-£7,000.
Not necessarily, but it's advisable. Ofgem requires notification for generators above 16A (about 3.6kW). Most plug-in panels fall below that, but your supplier's terms and conditions may still require disclosure. Check your contract or call your supplier to avoid invalidating your home insurance.
