The vast majority of UK homes can accommodate a plug-in solar system without any electrical work beyond the standard installation steps. But there is one area worth checking before you buy, particularly in older properties: the type of RCD protection in your consumer unit.
What an RCD does and why it matters
An RCD, or residual current device, is a safety switch in your fuse box that detects certain types of electrical fault and cuts the power before they can cause a fire or electric shock. They come in different types, and the type fitted in older consumer units may not handle the way plug-in solar feeds power into a circuit correctly.
Older consumer units often contain Type AC RCDs. These were designed to handle the kind of current drawn by conventional appliances. A plug-in solar system converts DC electricity from the panels into AC and feeds it back into the circuit, which creates a small DC component in the current flow. Type AC RCDs were not designed for this and can in some cases fail to trip correctly if a fault occurs.
What type you need
For a circuit with a plug-in solar system connected, a Type A RCD or better provides the correct level of protection. Type A RCDs are standard in consumer units installed in the last fifteen years or so. If your home was rewired or had a new consumer unit fitted within the last decade, you are almost certainly fine.
For certainty, look at your fuse box. The RCDs will be marked with their type, usually as a letter A, AC or F on the casing or in the manufacturer’s documentation. If you cannot find this information or are not comfortable looking inside your consumer unit, a registered electrician can check for you in a short visit.
When you might need an upgrade
If your consumer unit contains only Type AC RCDs and is significantly old, an upgrade may be advisable before connecting a plug-in solar system. This is not a particularly expensive job, and a new consumer unit with appropriate RCD protection will improve the general electrical safety of your home as well as making it suitable for plug-in solar. If you are having a registered electrician connect your system anyway, asking them to check the consumer unit at the same time makes sense.
This applies to a small minority of homes
It is worth being clear: the consumer unit issue affects a relatively small proportion of UK homes. If your property has had any electrical work in the last fifteen years, or if your fuse box was replaced as part of a renovation, you are almost certainly in good shape. The check takes a few minutes and rules out a potential issue before it becomes a problem.
For the overwhelming majority of UK households, particularly those in properties built or rewired since 2010, plug-in solar connects without any need to touch the consumer unit at all.