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Smart tariff comparison: time-of-use vs standard
Enter your yearly electricity use and how much of it you could move into cheap off-peak hours, and see which tariff type would likely cost you least.
Defaults from our data file, last updated 2026-10-20.
Estimates only, not financial advice. Results use average UK figures and the assumptions shown. Your real costs depend on your home, tariff, region and installer quotes. Always get several quotes from certified installers and check current tariff rates before deciding.
How time-of-use tariffs work
A standard variable tariff charges the same price for every unit, whatever the time of day. Time-of-use tariffs charge less during certain hours, usually overnight, and sometimes more at other times. Economy 7 is the oldest version, with seven cheaper night hours. Modern smart tariffs need a smart meter and offer much cheaper windows. Octopus Go, for example, has a four-hour overnight window aimed at EV drivers, and Cosy Octopus offers several cheap slots during the day for heat pump owners. Agile tariffs change every half hour with wholesale prices, so they can't be modelled with a single fixed figure and aren't included here.
Whether a time-of-use tariff saves you money depends on one thing: how much of your electricity you can move into the cheap hours. EV charging, battery charging, hot water cylinders, heat pumps and dishwashers on timers can all be shifted easily. Cooking, lighting and TV mostly can't.
How we calculate it
For each tariff we split your yearly use into off-peak and peak portions using the share you enter, price each portion, and add the yearly standing charge. On the standard tariff everything is charged at the single price cap rate. The cheapest option comes first.
The rates we use (and their limits)
- Standard variable: 26.32p per kWh and 54.83p per day, the Ofgem price cap average for Direct Debit customers from 1 October to 31 December 2026.
- Octopus Go: an off-peak rate of about 8.21p per kWh, the average after the 1 October 2026 change according to an independent tariff log. The day rate (we assume about 26.5p) and standing charge are estimates.
- Cosy Octopus: rates ranged from about 11.83p to 40.03p across its time bands from 1 October 2026. We simplify this to a 14p cheap rate and a 40.03p peak rate, which is an estimate. Cosy's mid-price daytime band sits between those, so for heavy daytime users this rough model is pessimistic.
- Economy 7: typical day and night rates of about 32p and 15p are an estimate. Ofgem publishes regional multi-rate cap figures that vary widely.
Rates vary by region, and smart tariffs change often, so treat the result as a guide to which type of tariff suits you, then check the live rates for your postcode. All rates are kept in our editable data file and reviewed each quarter.
Worked example
A home using 2,500 kWh a year (Ofgem's current typical figure) pays about £858 on the price cap including standing charges. If it moves 30% of its use off-peak, Octopus Go comes to about £725, a saving of around £130. An EV driver using 5,000 kWh with 60% off-peak would pay roughly £1,516 on the standard tariff and about £976 on Go, a saving of around £540. A household that can only shift 10% may find a time-of-use tariff barely helps, or costs more if peak rates are higher.
Tips before switching
- Look at your smart meter's half-hourly data (available in most supplier apps) to see when you really use power.
- Check eligibility. Some tariffs need a particular EV, charger, battery or heat pump.
- Check exit fees on fixed versions, and whether your export tariff depends on staying with the same supplier.
- Remember the price cap changes every quarter. The next change is due on 1 January 2027.
FAQs
Is Economy 7 worth it?
Usually only if you use a large share of your electricity overnight, for example with storage heaters. Otherwise the higher day rate can cost you more.
Do I need a smart meter for time-of-use tariffs?
Yes, modern half-hourly tariffs such as Go, Cosy and Agile need a working smart meter.
What off-peak share is realistic?
Households without an EV, battery or electric heating often manage 10–25%. With an EV or battery, 50–70% is common.
Why is Agile not included?
Agile prices change every half hour with the wholesale market, so a fixed-rate comparison would be misleading.
Related calculators
Sources
- Ofgem – Energy price cap unit rates and standing charges (1 Oct–31 Dec 2026)
- Ofgem – Changes to energy price cap 1 October to 31 December 2026
- Energy Review – Octopus price change log (Oct 2026)
- Ofgem – Review of typical domestic consumption values: decision (2026 TDCVs)
Estimates only, not financial advice. Results use average UK figures and the assumptions shown. Your real costs depend on your home, tariff, region and installer quotes. Always get several quotes from certified installers and check current tariff rates before deciding.