Key takeaways
- • Plug-in solar in Great Britain is limited to a maximum output of 800W.
- • Savings depend heavily on how much electricity you use during daylight hours.
- • Permission may be required if you rent, lease or live in a managed building.
The microinverter is the component that makes a plug-in system legal, safe and grid-friendly. It deserves more attention than the panels.
What it does
It converts DC from the panels into 230V, 50Hz AC that matches the grid waveform, and synchronises with it. It also performs maximum power point tracking, constantly adjusting to extract the most power available in current light conditions.
Anti-islanding
If the grid fails, the microinverter must stop generating within a fraction of a second so it cannot energise a dead network. This is mandatory under G98 and is why plug-in solar does not work in a power cut.
Why output is capped
Rules and certifications are written around inverter output rather than panel capacity. An 800W inverter fed by 900W of panels simply clips the rare peak while producing more in low light — a normal and beneficial design choice.
String inverters versus microinverters
Microinverters sit per panel or per pair, so shading on one panel does not drag down the other. String inverters are cheaper per watt at scale but suffer from mismatch. For small plug-in systems, microinverters are standard.
What to check when buying
Certified G98 output rating, efficiency around 95 percent or better, IP65 or better enclosure rating, warranty length, and whether monitoring is included and works without a subscription.
Frequently asked questions
Sources
Fact-check status: reviewed. Read our editorial policy. General information only — not electrical, legal or financial advice.