EV tariffs explained: off-peak charging windows, prices and how employers should reimburse them

An EV tariff is an electricity tariff that sells a cheap window, usually four to seven hours overnight, at roughly 7p to 9p per kWh, against 26.32p on the standard price cap rate for October to December 2026. Charging inside that window cuts the cost of a mile by about two thirds.

This guide explains the four families of tariff (Economy 7, fixed EV windows, smart tariffs and half-hourly tariffs), what each needs, how much you save on a typical mileage, and how to schedule charging. The last part is for employers: why paying one flat rate per mile over-pays some drivers and under-pays others, and how valuing each session at the driver's own tariff, as Voltaback does, fixes it.

Off-peak charging in the UK: the basics

Electricity is cheaper at night because demand is low and wind output is often high. Suppliers pass part of that on through time-of-use tariffs, and the government pushes in the same direction: since 30 June 2022, every home and workplace chargepoint sold in Great Britain must be smart, with default charging hours outside the grid's peak periods, which the regulations define as 8 am to 11 am and 4 pm to 10 pm on weekdays.

So the question is not whether to charge off-peak, but which tariff turns that into the biggest saving for your home.

Source: Smart charge point regulations, gov.uk.

The four types of off-peak tariff

Economy 7 and Economy 10

The oldest form of off-peak tariff, designed for storage heaters. It works on an old two-register meter, which makes it the main option if you have no smart meter. The night rate is cheaper than the standard rate but usually less cheap than a dedicated EV tariff, and the day rate is higher, so it only pays off if you move a large share of your consumption to the night.

Fixed EV windows

The most popular form. Examples from What Car?'s May 2026 comparison: Octopus Go at 8.5p from 00:30 to 05:30, EDF GoElectric at 6.99p from 23:00 to 06:00, E.On Next Drive Smart at 8p from midnight to 06:00, British Gas at 9p from midnight to 05:00. The cheap rate applies to the whole home during the window, so a dishwasher or washing machine on a timer benefits too.

Smart EV tariffs

With Intelligent Octopus Go, for example, you tell the app when the car must be ready and the supplier decides when to charge, inside a 23:30 to 05:30 window plus extra slots when the grid has spare capacity. Octopus bills those smart slots at the off-peak rate. The trade-off: you need a compatible car or charger, and you hand over control of the schedule.

Half-hourly tariffs

Octopus Agile is the best known. Prices change every half hour and can fall very low, occasionally below zero, when wind output is high, but they can also spike in the evening peak. It suits drivers who automate charging around the cheapest slots, and it is the hardest to value for reimbursement, since each half hour has its own price.

Rates change often: suppliers revised EV tariffs in spring 2026, and the prices above were collected before the VAT cut on domestic electricity. Always check the supplier's own page before switching. This guide does not recommend one supplier over another.

Sources: What Car? EV tariffs, Octopus Agile.

Do you need a smart meter for an EV tariff?

For almost all of them, yes. A time-of-use tariff needs half-hourly or at least time-stamped readings, which a smart meter sends automatically. Economy 7 is the exception, as it can run on a two-register meter.

Coverage is high: according to the Department for Energy Security and Net Zero, 72 % of meters in Great Britain were smart or advanced at the end of June 2026. If you are in the remaining group, your supplier installs a smart meter at no upfront cost. The guide to charging without a smart meter covers what you can still do in the meantime.

Source: Smart meters in Great Britain, quarterly update June 2026.

How much do you save by charging off-peak?

Take 8,000 miles a year, all charged at home, at HMRC's assumption of 3.59 miles per kWh: that is about 2,230 kWh.

The saving from moving to an EV window is about £400 to £430 a year on that mileage. An Economy 7 night rate sits between the two, depending on your supplier and region, so it saves less. In winter, or with a large SUV, real consumption is often nearer 3.1 miles per kWh, which makes the saving larger still.

Two caveats:

• Standing charges differ between tariffs, and they apply whether you drive or not.
• Your daytime rate may be higher on an EV tariff than on the price cap. If your household uses a lot of electricity during the day and cannot shift it, compare the full annual bill, not only the night rate.

From 1 October 2026 to 31 March 2027, domestic electricity in Great Britain carries 0 % VAT instead of 5 %. Public chargers keep 20 % VAT, which widens the gap between home and public charging. The cost of charging at home and the price per kWh guide go into the full calculation.

Sources: Ofgem price cap, October to December 2026, Zapmap charging price index, Revenue and Customs Brief 10 (2026).

How many miles fit into an off-peak window?

The window length and your charger's power set how far you can drive on cheap electricity alone. At about 3.1 miles per kWh, allowing for charging losses:

With a 7 kW wallbox, a five-hour window covers 100 miles a night, enough for almost any commute. With a 3-pin plug, a short window may not cover a long day, and the rest of the charge will run into the dearer day rate unless you stop it.

How to schedule charging in the cheap window

1. Find your exact window. It is in your tariff documents or the supplier app. Economy 7 times depend on your meter and region; check them rather than assume midnight to 7 am.
2. Choose one scheduler. Either the car's app or the wallbox app, not both: two schedules fighting each other is the most common reason a car does not charge.
3. Set a departure time and a charge limit, for example 80 % on weekdays. The car will start late enough to finish on time.
4. On a smart tariff, let the supplier control the charge and only set the target and departure time.
5. Check after a tariff change. If your window moves, update the schedule the same day. A smart charger sold since mid-2022 starts with default off-peak hours, which may not match your tariff's window.
6. Look at the sessions after a month. If some sessions start before the window, there is a "charge now" override or a second schedule somewhere.

Cheap electricity in the afternoon: who it helps

Off-peak is not only a night-time story. Economy 10 meters usually add a few cheap hours in the afternoon and evening on top of the night block, and half-hourly tariffs often show low prices around midday on sunny, windy days, when solar output is high and demand is moderate.

This is useful for three kinds of driver:

• Shift workers and night drivers, whose car is at home during the day rather than at night.
• Homes with solar panels, which can charge the car from their own surplus at midday and keep the grid tariff for the night.
• Drivers on Agile or similar tariffs, who let an app pick the cheapest half hours whenever they fall.

For a classic 9-to-5 commuter, the car is away at midday, so the night window remains the one that matters. Avoid the weekday evening peak in any case: on most time-of-use tariffs, 4 pm to 7 pm is the dearest part of the day.

Choosing a tariff: a five-point checklist

1. Your meter: smart meter in smart mode, two-register meter or neither. This decides which tariffs you can join.
2. Your car and charger: smart EV tariffs only work with listed cars or chargers. Check compatibility before you switch.
3. Window length vs mileage: a four-hour window and a 3-pin plug will not cover a 100-mile day.
4. Full annual cost: night rate, day rate and standing charge, on your real consumption.
5. Exit terms: fixed tariffs may carry exit fees; variable ones can change at short notice, as some EV tariffs did in spring 2026.

Is an EV tariff worth it?

Usually yes, if three conditions are met:

• You charge at home most of the time. The more home miles, the larger the saving.
• You can shift the car's charging to the night, which nearly every driver can.
• Your daytime consumption is moderate, or you can move part of it (washing, dishwasher, hot water) into the window.

It is less clear-cut for very low mileage drivers with high daytime use, for example working from home with electric heating. In that case compare annual quotes on both tariffs with your real consumption.

Does charging overnight damage the battery?

No. Slow AC charging overnight is the gentlest way to charge a lithium-ion battery. What matters more is not sitting at 100 % for long periods: set the daily limit your manufacturer recommends, often 80 %, and charge to full before long trips only.

The employer's view: valuing off-peak charging fairly

For company car drivers, the tariff is not only a personal saving. It decides how much the employer pays, depending on which reimbursement method it uses.

Why a flat rate per mile over-pays some drivers and under-pays others

HMRC's Advisory Electricity Rate (AER) for fully electric company cars is 7p per business mile for home charging and 15p for public charging, from 1 September 2026. HMRC builds it on 3.59 miles per kWh, which makes 7p a mile equivalent to about 25p per kWh. At a more realistic year-round 0.32 kWh per mile, 7p a mile pays about 21.8p per kWh.

So, on 10,000 business miles a year at 0.32 kWh per mile:

Two drivers doing the same job get very different outcomes because of a tariff choice. And the AER covers business miles only: the private miles of a company car stay on the driver unless the employer repays them.

Source: Advisory fuel rates, HMRC.

What the company pays: a 50-car example

Take 50 company EVs, each doing 10,000 business miles a year, with half the drivers on an EV tariff at 7p and half on the price cap rate.

• AER at 7p a mile: 50 x £700 = £35,000 a year.
• Real cost per session: 25 x £224 + 25 x £842 = £26,650 a year.

Real-cost reimbursement is about £8,000 cheaper here, because the company stops paying 21.8p for kWh that cost 7p, and nobody is left out of pocket. With real cost, the employer can also choose to repay private miles tax free, because HMRC allows it for company cars.

Valuing each session at the tariff in force

The fair method is to value each charging session at the driver's tariff at the time of charging: 7p for a session inside the window, the day rate for a top-up at 6 pm, the half-hourly price on Agile. A single average price per month is simpler but loses exactly the information that off-peak tariffs create.

That is what Voltaback does. It reads each home session from the car (more than 48 brands, no box to fit), applies the driver's tariff schedule to it, and produces a monthly amount ready to import into payroll. Voltaback relies on the home's MID-certified meter, not on a standalone cable meter, for the household price, and the company never receives the car's location. You can estimate the cost for your own fleet with the home charging cost simulator.

Behaviour: who keeps the off-peak saving?

With a flat AER, the driver keeps the difference, so the AER gives drivers a reason to switch to an EV tariff and charge at night. Some UK fleets value exactly that.

With real-cost reimbursement, the incentive moves to the company: every kWh shifted into the cheap window shrinks the company's bill, not the driver's. You do not need to rely on drivers' goodwill. Per-session data shows who charges at peak times, and a simple policy line does the rest: "We repay the real cost of your home charging at your tariff; we ask you to use an EV tariff and to charge in its off-peak window when you can."

The employer's guide to home charging covers the full policy, and the guide to HMRC electric car mileage rates covers the AER rules in detail.

Off-peak charging, fairly reimbursed

An EV tariff is the easiest saving an EV driver can make, and for a company car fleet it should also be a saving for the employer. A single rate per mile cannot do both, because drivers' tariffs differ by a factor of three or four.

Voltaback values every home session at the driver's real tariff, at the time of charging, from the car's own data. See how home charging reimbursement works, or talk to our team about your fleet.