When is electricity cheapest?
Guide · updated 2026-08-23
On a flat tariff, never — you pay one rate whenever you use it. On any time-of-use tariff, the answer is overnight, and the gap is bigger than most people expect.
The shape of a normal day
Demand on the GB grid follows people. It bottoms out around 03:00-05:00, climbs through the morning, dips slightly at midday and peaks hard between roughly 16:00 and 19:00 as the country comes home, cooks and turns the lights on. That evening peak is met by the most expensive plant on the system, which is why it costs the most.
Wind changes the picture more than time of day does. A windy night can drive the wholesale price below zero; a still, cold evening in January is the most expensive electricity of the year. This is why a tariff that follows the market is worth watching rather than memorising.
What it is worth in money
On a flat tariff, nothing. On Economy 7 the night rate is typically around half the day rate. On Agile the spread within a single day is routinely three or four times, and occasionally the cheap end is negative, meaning you are paid to use it.
Concretely: a washing machine cycle uses somewhere around 0.5-1 kWh, a dishwasher 1-1.5 kWh, a tumble dryer 2-4 kWh. Moving all three out of the evening peak on a half-hourly tariff saves a few tens of pence a day — call it £30-£80 a year, for the price of pressing a delay-start button. An EV charging 40 kWh overnight instead of at teatime is worth many times that.
Finding tonight's cheapest window
Guessing is unnecessary. Tomorrow's half-hourly prices are published each afternoon, and the cheapest-window finder shows the cheapest run of consecutive half hours still to come, from 30 minutes up to six hours — pick the length that matches the appliance and set the timer.
If you would rather not look, alerts will tell you when a cheap window or a negative price is coming, or when the peak is about to start.
Things not worth moving
A fridge, a freezer and a router run continuously and cannot be shifted. Lighting is trivial on LEDs. Cooking is hard to move because people eat in the evening. The wins are concentrated in a very short list: EV, hot water, heating, laundry, dishwasher, battery. Everything else is rounding.
Common questions
What is the cheapest time of day to use electricity?
Overnight, typically between about 23:00 and 06:00, and cheapest of all in the small hours when demand is lowest. On tariffs that follow the wholesale market, windy nights are cheaper still and can go negative.
Is it cheaper to run a washing machine at night?
Only on a time-of-use tariff such as Economy 7, Octopus Go or Agile. On a single-rate tariff the price is the same at 03:00 as at 18:00.
Why is electricity most expensive between 4pm and 7pm?
That is when national demand peaks, so the most expensive generation on the system has to run to meet it. Network charges are also weighted towards that window.
See it on your own numbers. halfhourly.uk shows live half-hourly prices for every GB region for free, and if you connect an Octopus account it prices your own smart-meter readings against every tariff.