Economy 7 Savings Calculator

This Economy 7 savings calculator shows UK households whether an Economy 7 tariff is cheaper than a standard single rate tariff, using your own day rate, night rate, standing charges and share of night time use, with Ofgem's October to December 2026 price cap as the default comparison. It gives your yearly saving or extra cost, the exact Economy 7 break even point for your rates, and how many kWh you would need to move to the night hours to make it pay. Figures checked October 2026.

Quick answer: Economy 7 is worth it when your night share is above the break even point: (day rate minus single rate) divided by (day rate minus night rate). With a 32.50p day rate, 14.00p night rate and the 26.32p cap rate, that is 33.4%. The Economy 7 savings calculator works it out for your bill.

What Is an Economy 7 Savings Calculator?

An Economy 7 savings calculator is a tool that compares the yearly cost of a two rate Economy 7 electricity tariff with a single rate tariff for the same usage. Economy 7 charges a cheaper unit rate for seven off peak hours at night and a higher rate for the other seventeen hours, so it only saves money when enough of your electricity is used at night.

The formula in plain words: Economy 7 cost equals night kWh times the night rate, plus day kWh times the day rate, plus the daily standing charge times 365. The single rate cost is all kWh times the single rate, plus its standing charge times 365. The saving is the difference. The break even night share is the day rate minus the single rate, divided by the day rate minus the night rate, with any extra standing charge added to the top line as a cost per kWh.

How to Use the Economy 7 Savings Calculator

Step 1: Enter Your Usage

Choose how you know your usage. If you have an annual statement, switch to day and night kWh and type the two register totals. Otherwise enter total kWh a year and your best estimate of the share used at night. Ofgem's typical consumption figure for homes with multi register meters such as Economy 7 is 3,400 kWh a year, which is the default.

Step 2: Add Your Economy 7 Rates

Copy the day rate, night rate and standing charge from your bill or from the Economy 7 quote you are considering. The defaults are examples only, because Economy 7 rates differ by supplier and by region. Rates are in pence, so 32.50p is entered as 32.50.

Step 3: Add the Single Rate to Compare

The default single rate is the Ofgem price cap for direct debit customers from 1 October to 31 December 2026: 26.32p per kWh and 54.83p a day. If you only want the cost of one appliance at either rate, the kWh cost calculator handles single items in pence per kWh. For a full comparison, replace the default with a fixed tariff quote if you are weighing up a specific deal.

Step 4: Read Your Result

The headline shows how much Economy 7 saves or costs each year, with the monthly figure underneath. The box compares your night share with the break even share and tells you how many kWh you could shift either way. The table shows the yearly cost at 20% to 60% night use, which is useful if you are planning storage heaters or a timer on the immersion heater.

Is Economy 7 Worth It?

Economy 7 is worth it if you use more of your electricity at night than the break even share for your rates, which is usually somewhere between 30% and 40%. Below that point the higher day rate costs more than the cheap night rate saves, so a single rate tariff is cheaper.

Worked example: Gareth lives in a two bedroom flat in Swansea with night storage heaters and a hot water cylinder. He uses 3,400 kWh a year, 42% of it at night, on example rates of 32.50p by day and 14.00p by night with a 54.83p daily standing charge. His Economy 7 bill is £1,040.95 a year. The same use on the October 2026 cap single rate costs £1,095.01, so Economy 7 saves him £54.06 a year, about £4.50 a month. His break even is 33.4%, so he has room to spare. If he removed the storage heaters and his night share fell to 20%, Economy 7 would cost him £84.32 a year more than the single rate.

What Percentage of Electricity Should Be Used at Night on Economy 7?

You should aim to use at least the break even share at night, and the old rule of thumb is 40%, but the true figure depends on how far apart the three unit rates are. The wider the gap between the day and night rates, the lower the share you need. This table uses the same rates as the worked example, with 3,400 kWh a year.

Share used at night	Economy 7 cost a year	Single rate cost a year	Difference
20%	£1,179.33	£1,095.01	Costs £84.32 more
30%	£1,116.43	£1,095.01	Costs £21.42 more
33.4% (break even)	£1,095.01	£1,095.01	No difference
40%	£1,053.53	£1,095.01	Saves £41.48
50%	£990.63	£1,095.01	Saves £104.38
60%	£927.73	£1,095.01	Saves £167.28

To see what your night share actually is, divide the night register reading for a year by the total of both registers and multiply by 100. A home with a gas boiler and no electric heating typically uses far less than 30% at night, which is why many people who inherit an Economy 7 meter in a rented flat end up paying more than they need to.

Who Should Use Economy 7?

Economy 7 suits homes that can move large loads into the night hours, such as electric car charging, an immersion heater on a timer and night storage heaters, plus washing machines and dishwashers set to run overnight. It rarely suits a small flat with gas heating, where most use happens in the evening peak. Night shift workers who sleep by day may also do well on it.

Off peak hours are set by your meter, not chosen by you, and are often around midnight to 7am but vary by region. Some older meters stay on GMT all year, so in summer the cheap hours run an hour later by the clock. Check the times on your meter or bill before you set any timers.

Does the Price Cap Apply to Economy 7?

Yes, but Ofgem caps the combined charge for a typical multi rate customer rather than each rate on its own, so a supplier can set a day rate above the single rate cap and still be within the rules. To estimate the rest of your energy bill, including gas, the energy bill calculator uses the same cap figures. Ofgem puts the cap level for a typical Economy 7 home at £1,046 a year for October to December 2026 by direct debit, which is why the day rate in this calculator is higher than the single rate default.

If you switch away from Economy 7, your supplier can usually bill a two register meter at a single rate, or a smart meter can be set to single rate remotely. If you are thinking of replacing storage heaters with a heat pump, the heat pump running cost calculator shows what that would cost to run on either tariff.

Frequently Asked Questions