Interim Product Specification, Version 2.0

One device, 800 VA, and no battery

The product specification sets what the device may be. The network connection rules set how many you may have. They are two different documents and they do not say the same thing.

The limits, and which document each comes from

800 VA maximum apparent power: At up to 253 V and 50 Hz. The statutory instrument separately puts the rated AC output at 800 watts. Those are not the same quantity and we will not pretend they are.
One device per household: The specification permits one per final ring circuit. The network rules are tighter and set one per household. The tighter one is the one you live with.
Up to four panels: Four modules may connect to one inverter, with no more than two in series in any string.
Three device shapes: One-component, where the panel and inverter are a sealed unit. Two-component, a panel and an inverter you connect. Multi-component, several panels and an inverter.
Outdoors needs IP55: If the plug and socket sit outside the building, the socket must be rated IP55 or better.
Residual current: Smooth DC residual current to the mains must not exceed 5 mA in normal operation or relevant fault conditions.

Batteries are not included, and that is the interesting part

The specification does not apply to plug-in battery systems, or to plug-in solar devices integrated with battery systems. A kit sold with a battery is outside the approved class.

This matters more than it sounds. Generation lands in the middle of the day, which is when many households use least. Without storage, whatever you do not use at the moment it is generated is simply exported. Respondents to the government consultation said exactly this: that by not permitting batteries, the potential payback to consumers was being reduced.

The government kept the exclusion anyway. So when you see a kit advertised with a battery, the battery is not covered by the specification that makes plug-in solar legal here.

Who is allowed to fit it

You are. That is the whole point of the product. But there is a line, and it is worth knowing which side of it you are on.

The whole class is defined around devices a household can put up and run without help from a trade. No electrician, no certificate, no MCS installer. You plug it in.

What you may not do yourself is change the building's electrical installation. The specification requires manufacturers to state that any testing or modification of the installation must be done by a professional electrician, and that where connection requires a change to the final circuit, for example replacing the circuit's overcurrent protection device, that is work only a qualified electrician may carry out.

You are also told to have an electrician inspect any socket you are unsure about, and to check whether the device affects your insurance. That last one is easy to skip and expensive to get wrong.

Need an electrician for the socket?

If the socket you had in mind is outdoors, or you are not sure it is sound, that is exactly what a fitting quote is for.

Tell us the postcode and what the surface is and we will put you in front of someone local who has actually read the new rules. If your answers show the permitted development right does not cover you, we will say so instead of sending anyone out.