Off peak tariffs and battery charging, window by window

The short answer

The cheapest off peak windows in the UK right now run for five to seven hours overnight, and they price electricity between 6.99p and 9p per kWh. The Ofgem price cap for 1 July to 30 September 2026 averages 26.11p per kWh. So a unit bought in the window costs roughly 65 to 73% less than the same unit bought at teatime. A battery is simply the thing that lets you move your evening into that window.

The overnight windows, checked on 3 August 2026

Rates taken from supplier pages on 3 August 2026. The British Gas rate is reported at around 7.9p with a Hive charger on Power plus, and its daytime rate at around 31p. Charge Anytime is a smart charging rate stated as at 4 November 2025 and applies to the car rather than to the whole property. None of these rates removes the standing charge, which the current cap averages at 57.19p a day.

The rates in that table sit close together, clustering between 6.99p and 9p, so the supplier you pick matters less than most people expect. The conditions are not close together at all, and the one that decides everything for a battery is whether the cheap price applies to the whole property or only to the car. Whole home pricing bills everything drawing power during the window at the off peak rate, including the battery filling up. Car only pricing discounts the charge point and leaves the rest of the house on the standard rate, which is no use to a battery. E.ON Next Drive, Intelligent Octopus Go and British Gas Electric Driver are listed as whole home. OVO Charge Anytime is a smart charging rate for the vehicle.

The window is usually the limit, not the battery

What one cheap unit is worth

Take the 8p rate. Against the 26.11p capped average, the raw gap is 18.11p on every unit. A battery does not give back everything you put into it, and we model a 10% round trip loss across this site, which is the pessimistic end. On that basis the unit costs 8.9p by the time it comes back out of the pack, so the real saving is about 17.2p per kWh. On EDF GoElectric Overnight at 6.99p the equivalent saving is a little over 18p. On a 9p tariff it is a little over 16p. The choice between them is worth pennies. The choice between having a battery and not having one is worth all of it, and how much a home battery saves, unit by unit multiplies those pennies out per night and per year.

• Whole home pricing. The single condition that decides whether a tariff works for a battery. If the cheap rate stops at the charge point, the battery pays the standard rate to fill.
• A window long enough for the pack. Seven hours on EDF, six on most, five on the shortest. Do the multiplication before you sign rather than after.
• A peak rate you can live with. Cheap nights are paid for with a dearer day. One EV tariff's daytime rate is reported at around 31p against a 26.11p capped average. A battery covers your evening block for you, so this usually works in your favour, but read the peak number first.
• The term and the exit fee. Several of these are fixed for twelve months. EDF GoElectric Overnight carries a £75 exit fee. Others carry none. Worth knowing before you switch.
• A smart meter sending half hourly readings. Time of use pricing cannot be billed without it. E.ON asks for half hourly consent, EDF for a fully connected smart meter. Sort this before the battery goes in, not after.

Daytime cheap windows, and why they matter in winter

Overnight is not the only cheap slot on the market. Cosy Octopus prices three windows a day at 51% below the regional day rate, at 4am to 7am, 1pm to 4pm and 10pm to midnight, with a peak from 4pm to 7pm at 50% above the day rate. British Gas Heat Power gives half price electricity from 1pm to 4pm and from midnight to 7am, 70 hours a week, applied as a weekly credit on the bill. E.ON Next Pumped splits the day into a super off peak block from 10pm to 6am, off peak from 6am to 4pm and 7pm to 10pm, and a peak from 4pm to 7pm, with the pence figures given at quote. All three are heating tariffs and need a heat pump, an electric boiler or electric heating in the property, so they are not open to everyone. Where they do apply, the afternoon window is genuinely useful in January, when the roof produces very little and one overnight fill may not carry the house through.

Solar changes which unit you should be using

Where OVO installs both the solar and the battery, you take your electricity supply from OVO and the system is under 30kW, the SEG Install Exclusive export rate is 20p per kWh. Solar only, with no battery, it is 15p. That rate changes the sums in a way most people do not expect. Using a unit of your own solar in the house saves the 26.11p you would otherwise have imported but gives up the 20p you would have earned by exporting it, so the real gain is about 6p. Filling the battery overnight at 8p saves about 17p on that unit instead, and your solar still goes out at the full 20p. The month by month working is on the strategy page, and our guide to the Smart Export Guarantee covers what qualifies for an export payment.

Octopus Flux is built around the same idea for battery homes, with the emphasis on the export side. It prices export in three blocks: roughly 29.32p per kWh from 4pm to 7pm, roughly 10.11p through the day and roughly 4.99p from 2am to 5am. Those are all export rates, so the tariff rewards you for holding charge until the late afternoon rather than releasing it overnight. The rates are regional, Octopus only shows them once you enter a postcode, and it does not publish the matching import rates without one either, so we do not quote one. Battery scheduling on Flux is set by you rather than automated. Intelligent Octopus Flux, the automated version, has been closed to new customers since April 2026.

1. Check the tariff is offered on your postcode. Some rates are regional and not published until you enter one.
2. Confirm in writing that the cheap rate applies to the whole property and not only to the charge point.
3. Read the peak rate, then work out what your daytime use costs on it.
4. Check the term and any exit fee before you switch, not after.
5. Make sure your smart meter is installed and sending half hourly readings first. Nothing here can be billed without it.
6. If you are exporting as well, check whether the export rate requires you to import from the same supplier.

Every rate on this page was taken from supplier pages on 3 August 2026, and tariffs move without much notice. Ofgem publishes the October to December 2026 price cap by 26 August 2026, to take effect on 1 October. Treat these figures as the shape of the market rather than as a quote, and confirm your own rate with your supplier. You can find your regional partner by postcode.