Why plug-in solar output is limited

Plug-in solar is small by design. Where a rooftop array might be several kilowatts spread across many panels, a plug-in system is usually one or two panels totalling a few hundred watts. That is not an accident or a shortcoming — it follows from what plug-in solar is for and how it connects to your home.

Before going further: Plug-in solar is not yet legal to use in the UK — the enabling regulations come into force on 27 August 2026, with connection standards still to follow. We cover the detail on the UK legal status page.

Small by design, not by accident

A plug-in system is meant to be simple and movable: a panel or two that feed your home through a single connection rather than being wired into the building. That design choice sets a natural ceiling on output. A large array needs fixed wiring, mounting and a central inverter sized for the whole roof; a plug-in kit is the opposite of that, so it produces a modest amount of power that a simple connection can carry.

How it compares with rooftop solar

The practical reasons for the limits

Much of the limit is simply practical. A movable kit that plugs in cannot sensibly carry the output of a large array, and it is meant to offset everyday background use rather than run a whole home. Connecting small generation to your home and the network also brings safety and notification considerations — the kind covered by the Energy Networks Association's engineering recommendations — which are more straightforward at modest output than at large scale.

The regulatory reason for the limit

On top of the practical limits, the rules now set a ceiling. Following its consultation, the Government set an 800W maximum rated AC output in the interim product specification given legal effect by SI 2026/848 (in force from 27 August 2026). This is an interim standard while enduring product standards are developed, not a final, settled figure, so we describe it as an interim cap rather than the last word on system size.

What a small system can realistically offset

Because the output is modest, a plug-in system is best thought of as a way to trim your daytime background load — the steady, low-level demand from a fridge, router, and devices on standby — while the sun is up. It will not run a kettle, oven or other high-power appliance, and only the electricity you use as it is generated reduces your bill; anything you do not use is exported. For a realistic sense of the numbers, see our guide on how much an 800W system can generate, and use the output calculator, which uses PVGIS data to estimate output for your specific postcode, orientation and tilt.