Don't take my word for it. This is what the Institution of Engineering and Technology has to say:

• Suitability of home wiring: Many installations - especially those that have not been professionally inspected for years - may contain worn components, unverified DIY alterations, or protective devices that cannot safely manage electricity being fed back into the system.
• Older RCDs may not work correctly with plugin generation: An RCD (Residual Current Device) is the safety switch that cuts the power if there’s a fault - for example, if someone cuts through a lawnmower cable it protects you against electric shock. But some older RCDs were never designed for electricity flowing back into the circuit, as can happen with plug-in solar. This can stop the RCD from tripping when it should, meaning it may not protect you during a fault. Households should check with a competent electrician whether their RCDs are suitable before plugging in any energy generation equipment.
• Compliance with Wiring Regulations: BS 7671 (the IET Wiring Regulations) sets out how electrical installations should be designed, built and verified. These regulations do not determine what consumers may plug in, placing responsibility on households to ensure that their wiring is fit for purpose before introducing any form of local generation.
• Risk of overload or back feed: Plug-in solar can create scenarios where parts of a circuit carry more current than intended, even if the circuit breaker appears to operate normally.
• Safe disconnection: Until appropriate standards are finalised, it is not guaranteed how different plug-in solar units will behave when more than one is connected, or how reliably they will disconnect during a power cut, posing a safety risk.

https://www.theiet.org/media/press-releases/press-releases-2026/press-releases-2026-january-march/24-march-2026-iet-urges-households-to-check-electrical-safety-before-using-plug-in-solar-products