Bills & Utilities
Economy 7 Break-even Calculator
Enter single-rate and peak/off-peak electricity rates to see whether Economy 7 saves money for your annual usage pattern.
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Ofgem GB Direct Debit rate examples: 1 October to 31 December 2026; checked 14 October. Gas includes 5% VAT; electricity has no VAT for this period. Enter your own bill rates; no extra VAT is added. Comparison quotes and usage are illustrative.
Useful next checks
- Check the inputs before relying on the result.
- Try a second scenario to compare outcomes.
- Read the guide below for context.
# Economy 7 Break-even Calculator
Estimate whether a UK Economy 7-style electricity tariff is cheaper than a single-rate tariff, and how much off-peak usage you need to break even.
What this calculator does
Economy 7 tariffs charge one rate for off-peak electricity and another rate for peak electricity. This calculator compares that with a single-rate tariff using annual kWh, standing charges, and your expected off-peak percentage.
How it works
Single-rate cost:
`annual kWh x single rate / 100 + single standing charge x 365 / 100`
Economy 7 cost:
`peak kWh x peak rate / 100 + off-peak kWh x off-peak rate / 100 + Economy 7 standing charge x 365 / 100`
The break-even point is the off-peak percentage where both tariffs cost the same.
Example calculation
For an illustrative 3,900 kWh a year, the single-rate example uses 26.32p/kWh + 54.83p/day. This gives £1,226.61 per year at unchanged rates.
Use fictional Economy 7 rates of 32p peak, 12p off-peak and 54.83p/day. At 42% off-peak, 1,638 kWh is off-peak and 2,262 kWh is peak. The annual Economy 7 estimate is £1,120.53, or £106.08 less than the single-rate example. With equal standing charges, break-even is `(32 − 26.32) / (32 − 12) × 100 = 28.4%` off-peak.
Only the single-rate rate/standing-charge pair is the published Ofgem average. The Economy 7 rates, including its illustrative equal standing charge, are not an official cap table or supplier offer. Replace all three with your own quote.
How to use the result
Use your actual annual kWh if possible. Then try several off-peak percentages, such as 20%, 40%, and 60%, to see how sensitive the result is to when you use electricity.
Assumptions and limitations
Off-peak times vary by supplier, meter, region, and tariff. This calculator compares arithmetic only; it cannot confirm whether you qualify for a tariff or whether your meter records peak and off-peak usage correctly.
Default rates and sources
Rate examples were checked on 14 October 2026 against Ofgem unit rates and standing charges for 1 October to 31 December 2026. They are Great Britain averages for Direct Debit, not Northern Ireland rates or a quote for every household. Regional, payment-method, meter and tariff differences matter; use your supplier's applicable rates.
Ofgem states that gas figures include 5% VAT, while electricity has no VAT from 1 October 2026 to 31 March 2027. Enter bill rates with any applicable VAT included: the calculator does not add VAT again. This VAT difference also means costs across the affected periods are not directly comparable. Bills crossing a rate-change date should be calculated separately for each part using its own usage, days and rates.
These examples expire after 31 December 2026; they are not a future tariff forecast. Annualised results assume the entered rates stay constant. Usage amounts and comparison offers are editable illustrations, not current official consumption benchmarks or live supplier offers.
Frequently asked questions
Is Economy 7 always cheaper if the night rate is lower?
No. The day rate or standing charge can be higher, so you usually need enough off-peak use to offset those costs.
What counts as off-peak usage?
Use the share of electricity recorded or expected during your tariff's cheaper period. Economy 7 is often overnight, but exact hours vary.
Can I use this for EV tariffs?
Yes, for a simple two-rate comparison. Specialist EV tariffs may have extra rules or different off-peak windows.
What off-peak percentage should I enter?
Use smart-meter or dual-rate meter data if available. Otherwise test scenarios, such as 30%, 50%, and 70%.
Does Economy 7 always run midnight to 7am?
No. Ofgem notes the cheaper period is often overnight, but the exact hours vary by supplier and location.