The Clocks Go Back on Sunday. Your Solar Peak Just Moved an Hour.

The sun doesn't change its clocks

At 2am on Sunday 25 October the UK clocks go back an hour, as the gov.uk clock change dates confirm. Your panels won't notice. The sun is exactly where it would have been anyway, and the day is under four minutes shorter than the one before.

What does change is the number on the clock when the sun is at its highest. Here are London's times for the Saturday and Sunday either side of the change, from sunrise-sunset.org:

Solar noon is the moment the sun is highest in the sky. South-facing panels often peak around then, but roof direction, shading and cloud can shift your own best window. These are London's times. The shift is the same one hour everywhere in the UK, and only the exact minutes move as you go east or west.

Why it matters if you plan around the sun

If you've been running the dishwasher or washing machine "at midday" because that's when your panels peak, that rule was built on the summer clock. In June the sun is highest at about one in the afternoon. From Sunday it's about quarter to twelve.

So the middle of your solar day moves earlier on the clock, and a schedule that was well placed on Saturday can quietly sit an hour late on Monday. On a bright day, late morning to early afternoon, roughly 11am to 1pm, is now the sweet spot.

Check your timers, because they don't all behave the same

I'd go through anything that starts on a schedule. They tend to fall into three groups:

• Follows the network clock. Phone-linked smart plugs and many app-controlled appliances update themselves when the clocks change. A cycle set for 12:00 still starts at 12:00, but that's now an hour later in sun terms. Move it an hour earlier.
• Has its own clock. Ovens and microwaves are the classic ones that need setting by hand, as this round-up of devices to change points out, while phones, TVs and smart meters usually change on their own. Appliance delay-start timers and plug-in timers vary, so check the manual or just look at the clock on Sunday morning.
• A plain dial timer. A mechanical dial has no idea what day it is. Leave it alone and it keeps firing at the same moment as before, which happens to keep it in step with the sun. If you reset it to the new clock time, move its pins an hour earlier to stay with the sun.

Winter is winter, so here's the honest bit

The light changes far more than the clock does. Good Energy's guide to summer and winter panel output puts the six months from April to September at roughly 65 to 75 percent of a year's generation, and October to March at about 25 to 35 percent. The day is about ten hours long now and falls to just under eight at midwinter.

Compliant plug-in solar kits became legal to buy and use in Great Britain on 27 August, so a lot of you are about to see your first autumn with panels. I'd rather say this plainly now than have you wonder in December: your panels will keep working, but on a grey day there may be very little to time around, and no schedule fixes that. What a schedule can do is make sure that when a bright window does turn up, you're using it.

A simple routine for the next few months

1. This weekend: go through any timer or schedule that touches your solar, and move the ones that follow the clock an hour earlier.
2. Each morning: look at the day's forecast before you choose a time. On a bright day aim for around 11am to 1pm. On a grey one, don't chase it.
3. Heavy loads: save washing, dishwasher and tumble dryer runs for the days the forecast shows a decent window, rather than holding to a fixed time.
4. In spring: the clocks go forward at 1am on Sunday 28 March 2027 and everything moves back the other way. Put a reminder in your phone now.

Where Sun Hours fits

Sun Hours gives you a 7-day forecast built around your own panels' best day, so you can plan around the weather and the daylight available. Check your forecast and appliance schedules after the clock change. It's free on iPhone and Android, and you don't need an account.

If something behaves oddly after the change, we'd like to hear about it on the support page.