Tariffs and grants / Tariff comparison and flexibility / EV tariff charge windows

T-037·Tariffs and grants / Tariff comparison and flexibility

EV tariff charge windows

Off-peak windows, managed charging and whole-home effects.

Tariff availability, rates and terms in this comparison were checked on 22 July 2026. They are a dated snapshot, so compare current address-specific quotes before acting.

An EV tariff charge window is the block of hours in which a time-of-use (TOU) electricity tariff charges a lower rate per kWh, usually overnight. The tariff splits the day into a cheap off-peak period and a more expensive peak period, so charging the car and other flexible household load can be moved into the cheap hours. The saving comes from the gap between the two prices and from how much electricity can be shifted into the window. Current rates must be compared from postcode-specific quotes because peak rates and standing charges vary by region and offer.

Suppliers set the window in one of two ways. A fixed window runs the same hours every night at a set rate. A smart or managed tariff lets the supplier decide when the car charges and can add cheap slots outside the standard overnight hours. The two behave differently for a home battery and for anyone trying to fit a large charge into a short window.

Fixed overnight windows

A fixed-window tariff gives the same cheap hours every night, so charging can be timed with a simple schedule on the car or the charger. These are two-rate tariffs: one off-peak price for the window, one higher price for the rest of the day. The whole home draws the off-peak rate during the window, not only the car.

The windows differ by supplier:

Tariff Off-peak window Length
Octopus Go 00:30 to 05:30 5 hours
E.ON Next Drive 00:00 to 06:00 6 hours
British Gas EV Power 00:00 to 05:00 5 hours
EDF GoElectric 23:00 to 06:00 7 hours
ScottishPower EV Saver 00:00 to 05:00 5 hours
So Energy So EV 00:00 to 05:00 5 hours

EDF GoElectric has a seven-hour standard window, longer than the fixed windows in this comparison. A longer window gives more time to finish a charge and more cheap hours for running other appliances. It does not by itself make the tariff cheaper because the daytime rate and standing charge still matter.

E.ON Next Drive’s current advertised fixed window is six hours, 00:00 to 06:00. Earlier tariff versions and third-party pages may show different hours. Rates on all these tariffs change over time and can vary by region, so a rate for a specific address only comes from a supplier quote.

Smart dispatch and managed charging

Instead of a fixed block, a managed tariff hands the timing to the supplier. It moves the car’s charging to times that suit the grid and can top up cheap slots outside the standard overnight hours.

Octopus Intelligent Go (IOG) keeps a guaranteed home off-peak window of 23:30 to 05:30 every night. Its current advertised smart-charge rate is 8p per kWh, subject to the customer’s quote. On top of the fixed window, Octopus can schedule the car in additional half-hour slots. The driver sets a ready-by time and Octopus fills the charge before then. An immediate bump charge outside the schedule is billed at the normal rate. IOG needs a supported EV or smart charger. Customers should read the current terms for how scheduled slots are applied to other household imports, particularly a home battery.

E.ON Next Drive Smart advertises an 8p/kWh smart-charging rate and uses the E.ON Next app to schedule a compatible setup. ScottishPower EV Optimise is also an 8p/kWh managed add-on, but it excludes 4pm to 8pm and cannot be combined with ScottishPower’s time-of-use Saver tariffs. British Gas EV Power+ provides managed charging through a compatible setup and applies its saving as account credit. The product mechanics matter because not every managed rate extends to all household electricity.

OVO Charge Anytime is an EV-only add-on rather than a whole-home window. Pay as you go currently reduces smart-charged electricity to 14p/kWh, subject to a £100 monthly credit cap. Four monthly plans instead include a set home-charging allowance and public-charging credit. Eligible Volvo customers using the Volvo Cars app have a separate 7p/kWh partnership rate.

The whole-home rate during the window

On the two-rate tariffs the off-peak rate covers everything the property draws during the window, not just the car. Running the dishwasher, washing machine or tumble dryer overnight, or heating water and charging a home battery then, all take the cheap rate and add to the saving. This whole-home benefit is the main difference between the two-rate tariffs and EV-only add-ons such as OVO Charge Anytime, where only the car sees the discount and the rest of the house pays its normal rate.

Intelligent Octopus Go’s six-hour cap

From January 2026 IOG limits cheap smart charging to six hours a day, measured midday to midday rather than by calendar day. The home off-peak window, 23:30 to 05:30, stays guaranteed regardless; the cap applies to the car’s smart charging. If the car charges beyond six hours, the extra half-hours are billed at the peak rate even when they fall inside the off-peak window. A Charge Cap setting lets the driver choose between stopping at the six cheapest hours or carrying on to hit the charge target at peak prices.

Octopus said 80% of sessions already used less than six hours. At a typical 7kW home charger, six hours delivers about 42kWh, roughly 120 miles for a fairly efficient car. Larger batteries can need more: one driver noted a full charge taking 11 hours, which now spreads across two days or spills into peak-rate charging. The cap was reported to affect around 260,000 drivers.

Home batteries and the charge window

A fixed-window tariff suits a home battery well. The battery can be set to charge during the predictable off-peak hours and discharge during peak, a simple reliable schedule. Smart tariffs complicate this. When IOG dispatches a daytime charging slot, the home battery sees a large household load and can discharge into the car, spending stored solar energy that was worth more than the tariff saved.

Octopus’s own guidance is to “blind” the home battery to the car charger so it does not drain into the EV. Blinding means configuring the inverter, its current-sensing clamps and the charger so the battery does not treat EV charging as ordinary household demand. Ohme makes the same point: its charger cannot tell battery power from solar power, so if the battery is set to discharge when the car plugs in, the charger may pull from the battery instead. The fixes are to set the battery not to discharge while the car charges, put it in hold mode or switch it off manually when plugging in. A common UK setup of a Solis hybrid inverter, a Zappi charger and IOG can leave each component working correctly on its own while the battery still empties into the car unnoticed. For an uncoordinated battery home, the lost stored-solar value can offset much of the tariff’s advantage.

Clock changes and the summer shift

Some suppliers move the off-peak window when the clocks change. ScottishPower’s window, for most smart meters, runs midnight to 5am in winter under Greenwich Mean Time (GMT) and shifts to 1am to 6am in summer under British Summer Time (BST). First-generation smart meters (SMETS1) made by LG, Itron or Aclara keep GMT-based timing all year, so the window does not move for those. Fuse Energy quotes its off-peak hours as 00:30 to 07:30 GMT, which points to a clock-adjusted window too. The upshot is that some drivers expect their window to shift when it does not, or the reverse, so check which hours actually apply before relying on them.

What the regulations require of the charge point

The EVs (Smart Charge Points) Regulations 2021, in force since 30 June 2022, set a baseline for home charge points. A charge point must default to off-peak charging hours under regulation 10, so a newly installed charger is set up not to charge during peak periods unless the owner overrides it. It must have smart functionality: able to send and receive information, respond to signals by varying the rate or timing of charging and provide demand-side response (DSR). It also must not be built to lose that smart functionality if the owner changes supplier.

Whether an off-peak window pays

All these tariffs need a smart meter, generally a second-generation SMETS2 unit or a compatible SMETS1, so the supplier can read half-hourly usage and apply the two rates. Activation time depends on the supplier and whether the existing meter is communicating correctly. Contract length and exit fees must be checked on the tariff information label or quote rather than inferred from the supplier’s other tariffs.

The value depends on how much electricity moves into the window. British Gas builds its EV-tariff savings estimates on 46% of a home’s electricity falling in off-peak hours. ScottishPower’s guidance is that below about 35% off-peak use a standard tariff can work out cheaper, because the peak rate on an EV tariff sits above a typical flat rate. For an EV-only home the choice between these tariffs is mostly about convenience; for a home with solar and a battery it also depends on whether the battery can be kept from draining into the car.

Applies to

EV charging

Last reviewed

22 Jul 2026