Smart EV tariff savings calculator UK
Compare a standard electricity tariff with an EV smart or time-of-use tariff. Include your EV charging, other household electricity use, peak and off-peak rates and standing charges.
How the smart EV tariff savings calculator works
A cheap overnight EV rate does not automatically mean the whole electricity tariff is cheaper. Some smart tariffs have a higher daytime rate, a different standing charge, or both.
This calculator therefore compares the annual electricity cost of both tariffs rather than looking only at the advertised off-peak rate.
Annual mileage ÷ EV efficiency
Annual EV electricity drawn:
EV battery energy ÷ charging efficiency
Current tariff EV cost:
Annual EV electricity × current unit rate
Smart tariff EV cost:
Off-peak EV electricity × off-peak rate + peak EV electricity × peak rate
Total tariff cost:
EV electricity cost + other household electricity cost + annual standing charge
Worked example
That requires approximately 2,924 kWh of electricity per year for EV charging.
At a flat rate of 26.11p/kWh, the EV charging electricity costs approximately £763 per year.
If 90% of that EV charging takes place at 8p/kWh and the remaining 10% at 30p/kWh, the EV charging cost falls to approximately £298 per year.
That is an EV-only saving of approximately £465 per year.
Once the example household electricity use and standing charges are also included, the estimated whole-electricity-tariff saving is approximately £368 per year.
Why household electricity matters
Your EV may use most of its electricity overnight, but the rest of your home still uses electricity during the day.
If the smart tariff has a higher peak rate, appliances, cooking, lighting, computers and other daytime electricity use can reduce the saving created by cheap EV charging.
Enter your annual household electricity use excluding the EV where possible. The calculator starts with 2,500 kWh as a reference value, based on Ofgem’s current medium single-rate Typical Domestic Consumption Value.
What does EV charging off-peak mean?
The EV off-peak percentage is the proportion of your annual charging electricity that you expect to buy during the tariff’s cheaper charging period.
If virtually all of your charging can be scheduled overnight, a high percentage may be appropriate. If you regularly need daytime home charging, use a lower figure.
What is the break-even percentage?
The calculator estimates how much of the EV’s electricity would need to be purchased at the cheap rate before the smart tariff’s total annual electricity cost matches the current tariff.
This calculation also includes the household electricity and standing-charge figures you entered. That makes it more useful than comparing the two EV unit rates in isolation.
Current electricity benchmark
The calculator currently starts with 26.11p/kWh and 57.19p/day for the current tariff.
These are Ofgem’s Great Britain average Direct Debit electricity figures for a standard variable tariff for 1 July to 30 September 2026.
From 1 October 2026, Ofgem’s average figures become 26.32p/kWh and 54.83p/day.
What this calculator does not model
It does not model half-hourly dynamic pricing, free charging periods, intelligent charging rewards, tariff caps, export tariffs, solar generation, home batteries or tariff-specific bonus payments.
It also assumes the percentages entered for peak and off-peak use are representative of a full year.
The result should therefore be used as a tariff-comparison estimate, not as a supplier quote or guarantee of future savings.
Frequently asked questions
What is an EV smart tariff?
EV and time-of-use electricity tariffs normally charge different unit rates at different times. A cheaper off-peak period can make scheduled overnight EV charging less expensive.
Is the cheapest off-peak EV tariff automatically the cheapest tariff?
No. The peak rate, standing charge, off-peak window and your household electricity use can all affect the total annual cost.
Why does this calculator include household electricity?
Switching electricity tariffs normally affects the electricity used by the whole home, not just the EV. A higher daytime rate can offset part of the saving from cheaper overnight charging.
Does the standing charge matter?
Yes. Even a relatively small daily difference is multiplied across 365 days, so the calculator includes both tariffs’ electricity standing charges.
What should I enter for EV off-peak charging?
Enter the percentage of your EV charging electricity that you realistically expect to buy during the cheap-rate period. Use less than 100% if you sometimes need to charge outside that window.
What should I enter for household off-peak electricity?
Enter an estimate of the proportion of your non-EV electricity use that occurs during the cheap period. Leaving it at 0% gives a more conservative comparison.
Do I need a smart meter for an EV smart tariff?
Many time-of-use and intelligent EV tariffs depend on smart-meter data, but eligibility and technical requirements vary by supplier. Check the specific tariff terms before switching.
Are the 8p and 30p rates current UK averages?
No. They are example figures used to demonstrate the calculator. Replace them with the actual off-peak and peak rates from the tariff you are considering.
Does the calculator include solar panels or a home battery?
No. Solar generation, battery storage and export payments can materially change the comparison and are not included in this calculator.