How does the Economy 7 Calculator work?

It compares the cost of a single standard unit rate against separate Economy 7 day and night rates, using your annual day and night usage. It adds any standing charge difference, then shows the estimated annual saving or extra cost. The figures are estimates based on what you enter.

What is the break-even night usage percentage?

It's the share of your total electricity that would need to fall in the cheaper night period for Economy 7 to cost the same as your standard tariff. Use more than that at night and Economy 7 tends to win; use less and the higher day rate tends to cost more.

Does Economy 7 always save money?

No. Economy 7 usually has a higher daytime rate, so it only tends to pay off if you can shift a meaningful share of usage to the off-peak night hours. This tool provides an estimate, not a guarantee.

Would Economy 7 suit your routine?

Cheaper overnight electricity isn’t always the cheaper option overall. Let’s compare your day and night usage with a single-rate tariff.

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Figures reviewed June 2026 and updated monthly where appropriate. All results are estimates.

Day electricity usage

Annual daytime usage in kWh.

Night electricity usage

Annual night-time usage in kWh.

Standard tariff unit rate

Pence per kWh.

Economy 7 day rate

Pence per kWh.

Economy 7 night rate

Pence per kWh.

Annual standing charge difference — optional

Any annual standing charge difference in pounds. Leave as 0 if unknown.

Enter all unit rates in pence per kWh and the standing charge difference in pounds per year. This tool provides an estimate, not a guaranteed bill amount, and Economy 7 does not always save money.

Enter your day usage, night usage and tariff rates to compare Economy 7 with a standard tariff.

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How the Economy 7 Calculator Works

The calculator compares the cost of a single standard electricity rate against separate Economy 7 day and night rates. It applies your standard rate to your total usage, then applies the Economy 7 day and night rates to your day and night usage separately, adds any standing charge difference, and shows the estimated annual saving or extra cost.

What Is Economy 7?

Economy 7 is a two-rate electricity tariff that gives you cheaper electricity during seven off-peak night-time hours, usually in exchange for a higher daytime rate. The exact off-peak window depends on your supplier and meter.

When Does Economy 7 Make Sense?

Economy 7 usually works best for households that can shift a meaningful share of their electricity use to the off-peak hours — for example running storage heaters, charging an EV or using appliances overnight. If most of your usage falls in the daytime, the higher day rate can outweigh the cheaper nights.

Why Economy 7 Can Be Confusing

Economy 7 can be hard to judge because suppliers use different off-peak time windows, rates vary by region, and the benefit depends heavily on equipment like storage heaters, immersion heaters and EV charging. Many households are also unsure exactly how much of their usage actually happens at night.

What Night Usage Percentage Do You Need?

The calculator estimates the break-even point — the share of your usage that would need to fall in the cheaper night period for the savings to outweigh the higher day rate. If your night usage percentage is above the break-even figure, Economy 7 tends to look favourable on your numbers.