Tariffs
Is Economy 7 worth it? Work out your break-even night share
Last checked: 15 October 2026 · SmartShift UK
Economy 7 has a cheaper night rate and a dearer day rate than a single-rate tariff. It only pays if enough of your electricity is used at night. That “enough” is a number you can work out from your own rates.
The break-even night share
Break-even night share = (day rate − single rate) ÷ (day rate − night rate)
Use the Economy 7 day and night rates and the single-rate price from the same supplier, for the same region and payment method. If more of your use than that share is at night, Economy 7 is cheaper on unit rates. Then compare standing charges, which can differ too.
Break-even night share: 34.1%.
Pre-filled with the worked example below. Replace them with the rates on your bill or quote.
Worked example (one supplier, one region, one day)
Flexible Octopus in London, Direct Debit, on 15 October 2026: single rate 26.60p; Economy 7 day 33.11p and night 13.99p. These are from Octopus’s own tariff data and are only here to show the method; they will differ in your region and change with the price cap.
- (33.11 − 26.60) ÷ (33.11 − 13.99) = 6.51 ÷ 19.12 = 34.1%.
- So on these rates you would need more than about a third of your electricity at night for Economy 7 to cost less in units.
- Example: a home using 2,000 kWh a year, 25% at night, pays 500 × 13.99p + 1,500 × 33.11p = £566.60 on Economy 7, against 2,000 × 26.60p = £531.91 on the single rate. At 45% at night it would be £490.11 against £531.91.
What can move to the night
The homepage timer-shift calculator uses these figures per run. Each run moved changes your night share:
| Load | kWh per run (calculator) | Moved 5 times a week | kWh a year |
|---|---|---|---|
| Dishwasher | 1.1 | 5 × 52 | 286 |
| Washing machine | 0.9 | 5 × 52 | 234 |
| Heat pump tumble dryer | 1.4 | 5 × 52 | 364 |
| Immersion heater | 2.0 | 5 × 52 | 520 |
Washing machines, dishwashers and dryers on a timer come with a safety caveat: London Fire Brigade advises against leaving them running overnight and unattended (see the dishwasher page). Immersion heaters are covered in immersion heater overnight.
Storage heaters
Storage heaters are designed to charge on cheap hours and release heat later. Citizens Advice says a time-of-use tariff such as Economy 7 or 10 usually works out cheaper for them. With storage heaters, the night share is often high enough that Economy 7 makes sense, but check it with your own figures.
Check before you trust your guess
Night share is easy to overestimate, because a lot of household use (cooking, lighting, TVs, the kettle) happens in the evening. Before deciding, look up your actual day and night kWh: they are on an Economy 7 bill, or in your supplier’s app if you have a smart meter. If you have an electric car, an EV tariff is usually the better comparison: see Economy 7 vs an EV tariff.
Questions people ask
Is Economy 7 worth it?
Only if enough of your electricity is used at night. Work out (day rate − single rate) ÷ (day rate − night rate) with your supplier’s rates. On Flexible Octopus London rates on 15 October 2026 the answer is 34.1%.
What percentage of electricity should be used at night on Economy 7?
More than the break-even share from your own rates. It varies by supplier and region, so calculate it rather than relying on a rule of thumb.
Is Economy 7 good with storage heaters?
Usually. Citizens Advice says a time-of-use tariff like Economy 7 or 10 typically works out cheaper for storage heaters, because they charge in the cheap hours.
Is this financial advice?
No. It is a formula and one dated example. Use your own bill and quotes.
Not financial advice. These are worked examples from published rates and EV-Database consumption estimates, for planning only. Your own tariff, day rate, standing charge, car, driving and weather will change the numbers. Check your bill and your supplier’s current terms before you switch or buy anything.
Sources
- Octopus Energy tariff API, Flexible Octopus (single-rate and two-rate prices by region)
- Citizens Advice, choosing an energy tariff (Economy 7 and Economy 10)
- Citizens Advice, using storage heaters and immersion heaters
- London Fire Brigade, bedtime checks
- Ofgem, energy price cap unit rates and standing charges (1 October–31 December 2026)
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