Economy 7 Calculator
Calculate domestic electricity costs using a dual-rate Economy 7 tariff. Compare peak daytime and off-peak overnight rates with standard single-rate electricity plans to maximize savings.
Economy 7 Calculator
💡 Economy 7 tariffs usually offer lower overnight electricity rates and higher daytime rates. Savings depend on how much electricity is used during off-peak hours.
How to Use Economy 7 Calculator
Estimating your dual-rate energy usage and comparing it with standard domestic tariffs is simple. Follow these step-by-step instructions to calculate your costs:
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1Enter day consumption. Input your total daytime energy consumption in kilowatt-hours (kWh) for the chosen billing period.
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2Enter night consumption. Input your off-peak overnight energy consumption in kilowatt-hours (kWh) for the same period.
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3Enter tariff rates. Type in the daytime and overnight rates in pence per kWh (p/kWh) specified by your UK energy supplier.
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4Enter standing charge. Input the daily standing charge in pence per day (p/day), which is the fixed cost to remain connected to the electricity grid.
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5Choose billing period. Select whether your entered consumption represents daily, monthly, quarterly, or annual electricity consumption.
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6Compare with standard tariff. Optionally enter your standard single-rate electricity tariff in pence per kWh to contrast overall expenses.
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7Review savings. Click calculate to review your total bill, standing charges, energy costs, and potential savings or extra costs.
How to Calculate Economy 7 Costs
To calculate Economy 7 costs, you must separate your daytime energy consumption from your off-peak overnight usage, apply the respective rates, and add the fixed daily standing charge. The following equations show how domestic electricity costs are calculated for dual-rate billing systems:
Economy 7 Cost Formulas
Formula 1 — Economy 7 Energy Cost:
Formula 2 — Standing Charge Cost:
Formula 3 — Total Economy 7 Cost:
Formula 4 — Savings or Extra Cost:
Step-by-Step UK Billing Example
Consider a typical UK household on a dual-rate meter with the following values:
- Day Usage: 250 kWh over a 30-day period
- Night Usage: 150 kWh over a 30-day period
- Day Rate: 28 p/kWh
- Night Rate: 12 p/kWh
- Standing Charge: 60 p/day
- Billing Period: 30 Days
- Standard Tariff Comparison: 25 p/kWh
Step 1 — Calculate Economy 7 Energy Cost
Multiply each consumption register by its rate, convert from pence to pounds, and sum them together:
Day energy cost = 250 kWh × 28 p/kWh = 7,000 pence = £70.00
Night energy cost = 150 kWh × 12 p/kWh = 1,800 pence = £18.00
Economy 7 Energy Cost = £70.00 + £18.00 = £88.00
Step 2 — Calculate Standing Charge Cost
Multiply the daily standing charge by the number of days in the billing period and convert to pounds:
Standing Charge Cost = 60 p/day × 30 days = 1,800 pence = £18.00
Step 3 — Calculate Total Economy 7 Cost
Sum the energy costs and standing charge costs together:
Total Economy 7 Cost = £88.00 + £18.00 = £106.00
Step 4 — Calculate Standard Tariff Cost
Find total usage first, apply standard rate, convert to pounds, and add standing charge:
Total Usage = 250 kWh + 150 kWh = 400 kWh
Standard Tariff Energy Cost = 400 kWh × 25 p/kWh = 10,000 pence = £100.00
Standard Tariff Cost = £100.00 + £18.00 = £118.00
Step 5 — Compare and Calculate Savings
Subtract the dual-rate Economy 7 cost from the single-rate standard tariff cost:
Savings = £118.00 − £106.00 = £12.00
Worked Example Final Results
- Total Period Consumption: 400 kWh
- Economy 7 Cost: £106.00
- Standard Tariff Cost: £118.00
- Net Period Savings: £12.00
Economy 7 Chart
The table below outlines typical outcomes for domestic energy accounts based on the proportion of electricity consumed during off-peak overnight hours. A dual-rate system requires a minimum amount of night usage to become financially viable.
| Night Usage Share | Typical Outcome |
|---|---|
| 0–15% | Usually higher bills |
| 15–30% | Little benefit |
| 30–45% | Moderate savings |
| 45–60% | Good savings |
| 60%+ | Maximum Economy 7 benefit |
Note: Actual financial savings depend on specific supplier tariffs, regional standing charges, and the overall household consumption profile.
Economy 7 Calculator Frequently Asked Questions
Economy 7 is a UK domestic electricity tariff that charges two different rates for electricity based on the time of day. It offers a cheaper off-peak rate for seven hours during the night and a more expensive peak rate during the day. This requires a dual-rate meter to track usage.
As the name implies, the off-peak period lasts for exactly seven hours. This typically runs from 11:00 PM to 6:00 AM, 12:00 AM to 7:00 AM, or 1:00 AM to 8:00 AM. The exact hours depend on your location, electricity supplier, and whether British Summer Time (BST) is active.
It is only cheaper if you shift a significant portion of your energy use to off-peak hours. Because daytime rates on Economy 7 are higher than standard single-rate tariffs, users who do not use night-storage heaters or run major appliances overnight often end up paying higher overall bills.
You can check your electricity bill for two separate rates (often labeled 'Day' and 'Night', or 'Low' and 'Normal'). Physically, older dual-rate meters show two separate dial readings, while smart meters allow you to scroll through and view active register readings for rate one and rate two.
High-load appliances that can be run overnight benefit the most. These include electric night-storage heaters, hot water cylinders, washing machines, tumble dryers, dishwashers, and electric vehicle (EV) home charging stations. Running these during off-peak hours maximizes savings.
Yes, you can switch to a standard single-rate tariff. Depending on your supplier, they may need to replace your dual-rate meter with a standard meter, configure your smart meter to read a single rate, or simply combine both readings on your bill. Some suppliers charge a fee for meter exchanges.
Economy 7 is specifically designed to save money for homes with electric night-storage heaters and hot water tanks. These systems draw energy to heat up overnight at the cheaper rate, then release the heat during the day without consuming expensive peak-rate daytime electricity.
Generally, you need to use at least 30% to 40% of your total electricity during the seven-hour off-peak night period to break even or save money on an Economy 7 tariff. If your night usage share is below 30%, you will likely get a lower bill by switching to a standard single-rate tariff.