According to the IET’s Mark Coles, there aren’t just hurdles to overcome, but issues so vast as to potentially derail the entire concept of plug-in solar in the UK. Coles is the IET’s head of technical regulations who has been developing standards for more than two decades. He said it “was a surprise to hear the announcement from the government,” and shared grave misgivings about the implementation of the program. In fact, the same day the government announced its plan to open up plug-in solar, the IET issued a warning. As well as reminding consumers that the systems aren’t yet legal, it urged people to get their home’s wiring checked out by a professional. “What may be safe in one home may pose a significant risk in another,” it said, “professional verification is the only way to be sure.”

For instance, the UK standards around Residual Current Devices (RCDs) were designed for one-way electrical traffic. “Think about your circuit breaker, your fusebox, you’ve got an electrical supply coming in, and cables going out to feed your appliances,” he said. When you put electricity on the final circuit, traveling in the opposite direction, you “can burn out the device because it’s not designed to take an electrical supply on that side.” It was only a few years ago that the UK opened up to bi-directional RCDs which can take two-way traffic, but even now, the older hardware is still “for sale now, still being installed now.” This isn’t just about an inconvenience to your wiring, either, since if an RCD fails, it could be fatal.

Coles added that, as much as Germany’s system has been lauded, it was able to launch on the basis of decisions made several decades prior. The wiring, plugs and consumer units in Germany are two-pole which is overall less safe than the British version, but much easier to accept power in from both ends. By comparison, “the plugs and sockets in the UK are not suitable for plugging an electrical source in,” said Coles. He added the rules covering British plugs “very clearly says you shall not plug in a low-voltage generating set [which is what a plug-in solar system is].” He also expressed concerns that as there was no universal standard for plug-in solar units, it would be impossible to offer certainty to regulators and consumers. And, as an additional risk, insurers may not pay out in the event of a fire given using such a system would break the rules around safe plug use.

If someone is still interested in getting a plug-in system, Coles advises them to get their wiring checked out by a qualified electrician. And, crucially, to brace themselves for the potential that they won’t be able to use it unless they have some or all of their home’s electrical systems re-wired at significant cost. “It isn’t just as simple as going to buy this unit and plugging it in,” he said.

Luke Osborne, technical director at Electrical Safety First, added his concerns around the issue of new technology coming into contact with older wiring. “Plug-in solar panels may negatively impact protective devices such as RCDs, which protect against electric shock,” he said. He also called for the government to “give clarity on how it will address these concerns,” to ensure “the UK boasts the best and safest solar panel roll out in Europe.”