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EV tariff savings calculator: whole-bill, with standing charges and day rates

Rates last checked: 15 October 2026 · SmartShift UK

Most EV tariff comparisons only multiply your car’s kWh by the off-peak rate. That flatters every tariff, because a whole-home EV tariff also changes the price of everything else you use in the day, and its standing charge can differ from your current one. This calculator prices the whole bill: car, house, standing charge, losses and how much of your charging really happens off-peak.

Rates last checked: 15 October 2026. Tariff figures come from UK EV tariffs compared. Where a supplier only gives a day rate or standing charge in a postcode quote, the box is left empty for you to fill in.

EV tariff Octopus region

EV tariff rates (p/kWh, p/day) Off-peak rate for the car Off-peak rate for the rest of the home Peak / day rate Standing charge (p/day)

Your current single-rate tariff Unit rate (p/kWh) Standing charge (p/day)

Pre-filled with Ofgem’s GB average cap for Direct Debit, 1 October–31 December 2026. Replace with the rates on your bill.

Your usage Miles a year Miles per kWh Charging losses (% of electricity drawn) Share of charging done off-peak (%) Other household use (kWh a year) Share of household use in the off-peak window (%)

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Current tariff, whole year: –
EV tariff, whole year: –
Electricity drawn: –
Break-even off-peak share: –

How it works: car kWh = miles ÷ miles per kWh, grossed up for losses. The off-peak share of that is billed at the car’s off-peak rate, the rest at the day rate. Other household use is billed at the home’s off-peak rate for the share you enter and at the day rate for the rest. Both tariffs include 365 days of standing charge. Break-even is the share of charging that has to be off-peak for the EV tariff to cost the same as your current one. Losses default to 0% to match the rest of the site; if you know yours, enter them.

A worked example

Current tariff: Ofgem cap, 26.32p/kWh and 54.83p a day. Typical EV (3.61 mi/kWh) doing 8,000 miles = 2,216 kWh, plus 2,500 kWh of other use = £1,441 a year.

Intelligent Octopus Go, London (7.6p off-peak, 35.88p day, 42.29p a day): all charging off-peak, no other use shifted = £1,220. Saving about £222. Move 20% of the other use into 23:30–05:30 and it is £1,078 (saving £363). Break-even: about 65% of charging off-peak.

A unit-rate-only comparison (2,216 kWh × (26.32p − 7.6p)) would say £415. The difference is the 35.88p day rate on the 2,500 kWh of other use, offset by the lower standing charge.

Region matters. Octopus’s day rates and standing charges for Intelligent Octopus Go run from 34.95p and 60.86p a day in Yorkshire to 38.82p and 66.74p a day in Merseyside and North Wales. Pick your region in the calculator. The full table is on UK EV tariffs compared.

What the calculator assumes

Every rate is from UK EV tariffs compared, checked on suppliers’ own pages on 15 October 2026. Nothing is estimated: if a supplier only quotes by postcode, the box is left blank.
Car-only offers (OVO Charge Anytime, ScottishPower EV Optimise) discount the car’s smart-charged kWh only. The rest of the home stays on your normal rate, so the calculator copies the day rate and standing charge from your current tariff.
British Gas’s 7.125p is its stated equivalent for car charging in Hive Power+ mode. The rest of the home gets EV Power’s 9.5p in 00:00–05:00.
Charger costs, exit fees and any monthly bolt-ons are not included.
The default 3.61 miles per kWh is the median of the 142 cars in EV charging costs by car.

Questions people ask

Does an EV tariff save money on the whole bill?

Usually, if most charging is in the cheap window. Using Ofgem’s cap (26.32p, 54.83p a day) as the current tariff, a typical EV doing 8,000 miles (2,216 kWh) plus 2,500 kWh of other use costs about £1,441 a year. On Intelligent Octopus Go in London (35.88p day, 42.29p a day standing charge) with all charging at 7.6p and none of the other use shifted, it is about £1,220: a saving of about £222, not the £415 a unit-rate-only comparison suggests.

What is the break-even off-peak percentage?

It is the share of your charging that has to land in the cheap window before the EV tariff costs the same as your current one. In the London example above it is about 65%. Below that, the higher day rate on everything else outweighs the cheap charging.

Why are some day rates blank?

Most suppliers only publish the day rate and standing charge in a postcode quote. Where a supplier hasn’t published them, the calculator leaves the box empty instead of guessing. Enter the figures from your quote.

Should I include charging losses?

Yes if you know them. Some electricity drawn from the wall never reaches the battery. The rest of this site leaves losses out, so the box starts at 0%. EV-Database’s manufacturer ‘rated’ consumption figures include charging losses and its ‘vehicle’ figures don’t, which is one way to see the gap for your car.

Is this financial advice?

No. It is arithmetic on published rates. Check your own quote and smart meter data before you switch.

Not financial advice. These are worked examples from published rates, for planning only. Check your own quote, bill and the supplier’s or manufacturer’s current terms before you switch or buy anything.

Sources

This page has no affiliate links. If paid links are added later, each one will be marked “paid link”. The calculators are free and run in your browser.