Solar cutting out on sunny days? Check your grid voltage

What I noticed

At a home I look after near Chester, the solar kept cutting out on bright summer afternoons, just when it should have been producing the most. The battery plans were off too, because the system was expecting more solar than it was getting.

The inverter logs told the story. The mains voltage at the house was regularly climbing above 253V, and every time it did, the inverter pulled its power back to protect itself.

Why high voltage switches solar off

In the UK, the voltage at your home is meant to stay between about 216V and 253V (230V, plus 10% or minus 6%). Solar inverters push power out onto the grid, and to do that they have to run at a slightly higher voltage than the grid itself. If the street is already near the top of the range, there's no headroom left.

So the inverter does what it's designed to do: it cuts back, or switches off for a while, to keep the voltage down. You lose free solar power, and if you're paid for export, you lose that money too. It tends to happen on the sunniest days, when lots of homes on the same street are exporting at once.

How to check your own system

1. Look for the pattern. Output that drops or flatlines around midday on clear days, especially at weekends and on bank holidays, when fewer people are using power.
2. Check the inverter app. Most show grid voltage. Look at a sunny afternoon. Readings sitting around 250V or above are a warning sign.
3. Look for fault codes. Messages such as "grid overvoltage" or "grid voltage high" in the event log are the giveaway.
4. Export the data. Most apps let you download readings as a spreadsheet. A few days of readings, with dates and times, is the evidence you'll need.

Who to contact (it isn't your supplier)

Voltage on the street is the responsibility of your network operator, the company that runs the cables and substations in your area. That's different from the supplier who sends your bills. You can find yours by postcode on the Energy Networks Association website, or by calling 105.

When you get in touch:

• Say clearly that the voltage at your supply is going over the 253V limit, and that it's making your solar inverter cut out.
• Send your evidence: dates, times and voltage readings, ideally the exported spreadsheet.
• Ask for a reference number and put it in writing. A formal written complaint gets taken more seriously than a phone call.

They may fit a monitor at your property for a while to confirm it, then adjust the settings at the local substation transformer. That one change can fix it for the whole street.

What I did, and how it ended

I pulled the inverter's voltage readings into a spreadsheet, wrote a formal complaint to the network operator using that data, and kept chasing it. While waiting, I set up an automation that eased the battery's output back whenever the voltage went over the limit, which kept the solar running more of the time.

If you think this is happening to you, start with the inverter app this weekend. It costs nothing to check, and the fix, when it comes, is free.

Last updated 9 October 2026. Every installation is different. This is my experience, not professional electrical advice.