How to calculate cycle cost (kWh x unit rate)
Calculating the cost of a washing machine cycle is straightforward. You need two numbers: the energy used in the cycle (in kWh) and the unit rate you pay (in pence per kWh).
Multiply them together to get the cost in pence. Divide by 100 for pounds.
For example: a 40°C cycle uses approximately 2kWh. At the July 2026 price cap rate of 26.11p/kWh, the calculation is 2 x 26.11 = 52.22p, rounded to 52p.
The kWh figure depends on two variables: temperature and load size. A 60°C cycle uses roughly 3kWh. A 30°C cycle uses roughly 1kWh. A 40°C cycle uses roughly 2kWh. These are typical figures for a modern 7-8kg front-loader. Older machines, particularly top-loaders from before 2015, may use 20-30% more energy per cycle.
The unit rate you pay depends on your tariff. Standard variable tariffs are pegged to the Ofgem price cap, set at 26.11p/kWh from July 2026. Economy 7 overnight rates run from approximately 10-13p/kWh. On Octopus Agile, the rate changes every 30 minutes and ranges from around 4p overnight to 38p at peak, with occasional plunge pricing events that can reach -20p/kWh.
The live Agile dashboard shows today's half-hourly rates so you can identify the cheapest window before setting your delay timer.
Cost on the price cap (26.11p/kWh)
The Ofgem price cap for July 2026 sets the unit rate at 26.11p/kWh. This is the rate that most standard variable tariff customers pay, regardless of time of day. There is no peak or off-peak distinction on a standard tariff.
On this tariff, a 40°C cycle (2kWh) costs 52p. A 30°C cycle (1kWh) costs 26p. A 60°C cycle (3kWh) costs 78p.
Households on a standard variable tariff pay the same 52p at 3am as they do at 6pm. There is no financial incentive to time your wash. The only saving on a standard tariff comes from temperature choice and load management.
If you wash daily at 40°C on a standard tariff, your annual washing cost is 52p x 365 = £189.80. Switching to 30°C for most washes brings that to 26p x 365 = £94.90. Temperature choice alone saves around £95 per year on a standard tariff.
The price cap figure covers England, Wales, and Scotland. Northern Ireland operates under different regulation and has a separate rate structure.
Cost on Economy 7 night rate (10-13p/kWh)
Economy 7 is a legacy time-of-use tariff available on standard electricity meters. It charges a lower rate for seven hours overnight, typically from midnight to 7am (exact hours vary by region and supplier). The daytime rate on Economy 7 is often higher than the standard price cap rate.
The Economy 7 overnight rate is approximately 10-13p/kWh depending on supplier and region. Using 11p/kWh as a representative figure:
A 40°C cycle (2kWh) overnight on Economy 7 costs 22p. A 30°C cycle (1kWh) costs 11p. A 60°C cycle (3kWh) costs 33p.
Economy 7 overnight rates are significantly cheaper than the standard price cap rate. The catch is the daytime rate. Economy 7 daytime rates typically run to 30-35p/kWh, which is above the price cap. If you run appliances during the day on Economy 7, you pay more than on a standard tariff. Economy 7 only saves money if you shift significant usage to the overnight window.
Washing machines are well-suited to Economy 7 because they can be easily scheduled to run overnight using the delay start function. But Economy 7 does not offer the flexibility or the price depth of Octopus Agile.
Cost on Agile: peak vs overnight vs plunge pricing
Octopus Agile sets a different rate for every 30-minute slot throughout the day, based on wholesale electricity prices. This creates a wide range of costs for the same cycle depending on when you run it.
At peak rate (approximately 38p/kWh, typically between 4pm and 7pm on winter weekdays), a 40°C cycle costs 76p. This is the most expensive time to wash on Agile and the figure that surprises most new customers.
At overnight rate (approximately 4p/kWh, typically between 2am and 5am), the same 40°C cycle costs just 8p. This is the headline number for Agile washing savings. The peak-to-overnight ratio on Agile can reach 8-20x, meaning the same cycle can cost anywhere from 8p to 76p depending entirely on when you press start.
Plunge pricing is a further benefit. Agile prices can go negative during high renewable generation periods, typically around 5-10 events per month. The floor is -20p/kWh. During a plunge pricing event, running a 2kWh cycle actually earns you approximately 40p rather than costing anything. The live dashboard highlights plunge pricing events in real time.
For the complete strategy around timing washes on Agile, the hub guide on the cheapest time to run your washing machine on Agile covers everything in detail.
The 30°C vs 40°C cost comparison at each tariff
The temperature you wash at makes a significant difference to cycle cost. Heating water is the most energy-intensive part of the washing process. A 30°C cycle uses roughly half the energy of a 40°C cycle, because the heating element runs for less time.
Modern detergents are formulated to clean effectively at 30°C for most household laundry. Heavily soiled items, towels, bedding, and any item with a hygiene concern should still be washed at 40°C or above. But everyday clothing, lightly worn items, and synthetics clean perfectly well at 30°C.
The table below shows the full cost comparison across all tariff types and temperature settings, including annual cost for a daily wash.
| Cycle type | Price cap 26.11p | E7 night 11p | Agile peak 38p | Agile overnight 4p | Agile plunge 0p | Annual cost (daily wash, Agile overnight) |
|---|---|---|---|---|---|---|
| 30°C / 1kWh | 26p | 11p | 38p | 4p | 0p | ~£14.60/yr |
| 40°C / 2kWh | 52p | 22p | 76p | 8p | 0p | ~£29.20/yr |
| 60°C / 3kWh | 78p | 33p | 114p | 12p | 0p | ~£43.80/yr |
The annual cost column assumes a daily wash at the Agile overnight rate. A household running a daily 40°C cycle on Agile overnight spends roughly £29 per year on washing electricity. The same household on a standard price cap tariff with no timing change spends £190 per year. The difference is £161 per year, from tariff choice and timing alone, with no change to wash temperature or frequency.
Annual bill impact: daily wash x 365 days
Most UK energy guides calculate appliance costs per cycle. The annual figure tells a more useful story for household budgeting.
A household running one 40°C wash per day, every day of the year, runs 365 cycles. At each tariff, here is what that costs annually:
Standard price cap (26.11p/kWh): 52p x 365 = £189.80 per year.
Economy 7 night rate (11p/kWh): 22p x 365 = £80.30 per year. This assumes every cycle runs during the overnight Economy 7 window, which requires daily use of the delay timer.
Agile peak (38p/kWh): 76p x 365 = £277.40 per year. This is the worst-case scenario for Agile customers who wash at 6pm every day without adjusting timing.
Agile overnight (4p/kWh): 8p x 365 = £29.20 per year. This is the best consistent rate achievable on Agile by timing washes to the cheapest overnight slots.
The saving from switching from price cap peak to Agile overnight, for a daily 40°C wash, is £189.80 minus £29.20 = £160.60 per year. This aligns closely with the £62-70 annual saving figure cited for timing changes alone (which assumes a mix of overnight and occasional off-peak washing, not perfect overnight timing every night).
On top of the timing saving, switching from 40°C to 30°C for most washes halves the energy used per cycle. A household running daily 30°C washes at Agile overnight rates spends just £14.60 per year on washing electricity. Combined with plunge pricing events that can reduce the cost to zero or below, the annual saving versus a standard tariff customer washing at 40°C exceeds £175 per year.
Use the live Agile price dashboard to check tonight's cheapest window and set your delay timer for maximum annual savings. The full picture of Agile timing for washing is in the complete Agile washing guide.
For the broader context of where your washing machine sits in your home's total electricity use, read what uses the most electricity in a UK home.