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.
Inputs
Results
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
If Economy 7 has a higher peak rate but a much lower night rate, it may only save money when enough usage happens overnight, such as storage heating, immersion heating, or EV charging.
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.
FAQs
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.
Related calculators
Frequently asked questions
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.