Britain green‑lights plug‑in solar kits – but experts warn of hidden electrical hazards

On 27 August the UK government gave the green light to plug‑in solar kits – those little box‑like panels you can simply set on a windowsill and plug into a wall socket. No installer, no planning permission, no certification fees – just a quick way to shave a few pounds off the electricity bill and, apparently, boost the nation’s renewable output.

Sounds easy, right? Well, engineers at the Institution of Engineering and Technology (IET) are raising their eyebrows. They argue that the rush to legalise these devices has outpaced the creation of proper safety rules, leaving a gap that could, in the worst‑case scenario, prove deadly.

One of the biggest worries centres on the residual current device (RCD) – the safety switch tucked inside most UK fuse boxes. An RCD is designed to sense stray current, like the kind that could electrocute someone, and trip within about 40 milliseconds. The problem? Most of the RCDs on British rooftops were built to handle current flowing in only one direction. Plug‑in solar panels push electricity back onto the grid, effectively reversing the flow, and the older RCDs might simply ignore the fault.

Then there’s the “islanding” dilemma. Imagine a street where several households have installed these kits. If the mains power goes out, each kit should automatically shut down. But if they keep feeding power into the local wires, they can fool each other into thinking the grid is still alive. In that situation, a line worker repairing the outage could be shocked by a hidden voltage that jumped past the fuse box.

Mark Coles, head of technical regulations at the IET, told us these issues were flagged long before the Department for Energy Security and Net Zero (DESNZ) closed its consultation on 30 June. “It was a done deal before it went out,” he said, “the process was rushed and we never got the time to draft a proper standard.”

Coles concedes the risk only materialises when a perfect storm of failures lines up, but he insists that with widespread adoption that storm becomes a matter of when, not if. The consequence could be an injury – or even a fatality – caused by an electrical fault that takes longer than the legal 40 ms to clear.

DESNZ replied that it had funded an independent lab to test plug‑in solar kits on typical UK wiring, concluding the devices were safe. However, the tests used brand‑new RCDs and kits that weren’t even legal in the UK at the time, meaning they might not reflect the older, heterogeneous equipment found in real homes.

“They spent money testing non‑standard units,” Coles added, “so the results don’t really tell us anything about what’s on the market now.”

What should a homeowner do? The IET recommends getting a qualified electrician to inspect the house’s wiring before plugging in a solar kit. It’s a small step that could catch an outdated RCD or highlight other wiring quirks that could turn a sunny savings plan into a safety nightmare.

Plug‑in solar panels could still be a useful tool in the UK’s renewable toolkit – provided the electrical under‑pinnings are up to the job. Until clear standards arrive, caution remains the best policy.