Best time of day to run appliances with solar panels

Why timing beats exporting

Here’s the whole game in one sentence: electricity you buy costs you roughly 26p/kWh on a standard tariff, while electricity you sell earns you anywhere from about 3p to 32p, depending on your supplier and tariff type. That gap is why the clock matters more than the brand of panel on your roof.

Every kilowatt-hour of your own sun that goes straight into an appliance saves you the full import price. Every kilowatt-hour you send down the wire only earns the pittance your export tariff pays. I’ve stood in enough kitchens to know this lands as abstract, so let’s make it concrete with the numbers I’ll use throughout this guide.

Shift a 3kWh tumble dryer cycle into the sun and you’ve saved about 78p of import. Let the panels export instead and run the dryer at nine o’clock, and you’ve earned 36p while spending 78p. Same panels, same dryer, a 42p swing — for doing nothing except moving a timer. Multiply that by every appliance in the house and you see why I bang on about this.

The Energy Saving Trust has been making the same point for years: self-consumed solar is the cheapest electricity a UK home will ever use.

The shape of a UK solar day

Solar output isn’t flat across the day. It’s a bell curve that peaks around 1pm British Summer Time on a south-facing roof, and the middle of that bell — roughly 10am to 4pm — is where two-thirds of your energy falls on a clear day. That’s your window. Everything in this article hangs off it.

Now look at the winter line. A crisp December day might give you the best part of nothing — a fifth of the summer peak, gone by half four. This is why any article that tells you to “always run appliances in the day” without mentioning the month is only half right. More on that below.

The appliance-by-appliance timetable

This is the table I wish someone had handed me twenty years ago. Summer windows assume a decent day from April to September; winter moves assume you’re on a sensible tariff.

The big three first. Washing machine and dishwasher are the easy wins: roughly one kilowatt-hour each, both happy on a delay-start, both small enough that a single bright hour covers them. The tumble dryer is the heavyweight — one cycle can drink more power than your panels make all day in November — so it’s strictly a bright-summer-midday machine in my house.

The immersion is the hidden one. Heating water with a 3kW element at two in the morning on imported power is the single most common waste of solar I see. A diverter trickles every spare watt into the cylinder through the day instead, and it pays for itself faster than most people expect. I’ve written a full guide to solar diverters and immersion heaters if that’s your setup.

And the EV. A car charger in solar mode sips only what the panels are making right now, which turns a 7kW load into a perfect surplus sponge. If you’re pairing panels with a car, see my piece on solar and EV charger combos.

Set-and-forget solar soaking

Nobody keeps this up by staring at an app all day. The households that actually save are the ones that automate it once and forget it. Here’s a clear July day in a well-set-up house:

• 7am Kettle, breakfast, showers. Small grid top-up, totally fine — it’s pennies.
• 10am Washing machine kicks in. Delay-start was set the night before.
• 12pm Dishwasher starts; EV charger switches to solar mode and sips the surplus.
• 2pm Tumble dryer, because the sky is blue. If it’s grey, it stays off.
• 4pm Diverter shovels the last spare watts into the hot water before the curve dies.
• 6–10pm Normal life. Telly, cooking, lights. Nothing heavy touches the grid.
• 10pm Nothing big on at all. Tomorrow’s sun is coming.

The toolkit is cheap: built-in delay-start timers on the white goods, a smart plug or two for anything without one, solar mode on the EV charger, and a diverter for the cylinder. Then spend one quiet week watching a decent solar monitoring app to learn where your own curve peaks. Every roof is a little different — shading, tilt, orientation — and your tenth of a kilowatt of homework here pays for years of free cycles.

Life with a battery: the rules change

Fit a battery and the whole conversation softens. Your midday surplus no longer leaves the house at 12p; it sits in a cupboard until teatime. Run the dishwasher at 7pm on stored sun and you’ve still avoided the 26p import — the saving is the same, the timing pressure isn’t.

But there’s a second-order trick most battery owners miss. On a bright day the battery is usually full by early afternoon, and everything after that spills out at the export rate. That’s the moment to fire up the heavy stuff — the dryer, the EV on solar mode, the immersion boost — because the alternative is exporting at a fraction of what you’d pay after dark. If you’re still weighing up whether the battery or the diverter comes first, my diverter vs battery breakdown covers it, and the best solar batteries UK 2026 guide has the current shortlist. There’s even a whole world of earning from a home battery once you’ve mastered the basics.

One genuine exception to everything above: on a handful of time-of-use tariffs — Octopus Intelligent Flux’s evening peak is the standout, paying up to 32p/kWh — the export rate can actually beat the 26p you’d pay to import. On those specific deals, deliberately draining a full battery back to the grid during the 4pm–7pm peak isn’t a mistake, it’s the correct move. It only works on that narrow window and needs the right tariff plus a compatible battery, so check you’re actually on it before assuming self-consumption always wins.

The only rule with a battery: glance at the charge before you start something big in the evening. Stored sun is free sun. A flat battery is 26p sun.

When the cheap grid beats the free sun

Time-of-use tariffs add a second clock to watch. On a half-hourly tariff like Octopus Agile, import prices often collapse through the middle of the day — exactly when your panels are producing — so midday becomes doubly cheap: free from the roof, near-free from the grid. And export prices on agile-style tariffs can flip negative on sunny spring weekends, which means the grid literally pays people to take power while your surplus is worth less than nothing. I’ve ranted about this properly in the grid is paying people not to use your solar — it’s the strongest argument yet for shifting loads to midday.

If you’ve got a heat pump, tariffs like Cosy Octopus carve out cheap daytime windows designed for exactly this kind of load shifting. If you’re exporting seriously, Flux-style tariffs pay for evening export instead. Choosing between them comes down to your hardware, and my Octopus Flux vs Cosy Octopus comparison is the place to start.

The winter reality check

Let me be blunt, because this is where well-meaning solar advice falls over: from November to February, timing your appliances around the sun is mostly a waste of effort. A clear December day on a 4kWp system might generate somewhere around 3 to 5kWh in total — a bit better than the month’s grey-day average of roughly 3.4kWh (December’s own generation is only about 105kWh for the whole 31 days), but squeezed into just a few hours around a very low midday sun. Enough to keep the fridge cold, run the router, and take a decent bite out of one appliance cycle if you time it right — nowhere near enough for a multi-appliance day.

So winter is tariff season, not solar season. Move the heavy loads into whatever cheap window your tariff offers — overnight for most, afternoon on agile-style deals — and let the panels contribute what they can. If you heat with a heat pump, its hot-water top-up is the one load still worth nudging towards bright midday spells, because even a weak sun shaves something off a 3kW element’s work. Come March, the bell curve returns and so does the 10-to-4 habit.

Six mistakes I keep seeing

• “Daytime” is not a window. Nine in the morning in April is not one in the afternoon in June. Aim for the middle of the bell, not just “before dark”.
• Delay-start set backwards. The cycle should run through midday, not finish as the sun peaks. Count back from the end time when you set it.
• Hot water at 2am. Importing power for the immersion overnight while the panels spill at midday is the classic. A diverter fixes it for a few hundred quid.
• Exporting at 3p, importing at 26p. If your export tariff is poor, self-consumption isn’t a nice-to-have — it’s the entire economics. Shop the SEG rate comparison regardless.
• Chasing negative prices by hand. Watching half-hourly export prices manually is a hobby, not a strategy. Automate it with smart kit or ignore it entirely.
• Still on the installer’s default SEG rate. Plenty of households are quietly sat on 3–4p because that’s whatever their installer’s network paid, without realising you can switch export supplier alone — no need to touch your import tariff. Ten minutes with your MCS certificate and MPAN can take you from 4p to 20p+. See the best SEG tariff rates for who’s paying what right now.

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