A home battery system is only as effective as the tariff behind it. Pair the wrong tariff with your battery and you could be leaving hundreds of pounds of savings on the table every year. Get it right, and the same hardware saves dramatically more.
This guide explains how time-of-use tariffs work, compares the leading UK smart tariffs available to battery owners in 2026, and shows you exactly what the savings look like in pounds at current electricity rates. Whether you're about to install a battery or looking to optimise an existing system, this is where to start.
What is a time-of-use tariff?
A time-of-use (TOU) tariff charges different unit rates for electricity depending on the time of day. During off-peak periods, typically overnight, rates are significantly lower than during peak demand periods in the morning and evening. On a flat-rate standard tariff, you pay the same price per kWh regardless of when you use it, so there is no financial benefit to timing your energy use.
Smart tariffs require a smart meter, which records your consumption in half-hour intervals and transmits the data to your supplier automatically. If you don't yet have a smart meter, your energy supplier will install one at no cost before switching you to a TOU tariff.
For home battery owners, TOU tariffs are the engine of savings. The battery charges during cheap off-peak periods and discharges during expensive peak periods, creating a financial arbitrage that reduces your net energy cost substantially.
Source: Ofgem, 'Smart tariffs and smart meters', 2024. ofgem.gov.uk
The leading smart tariffs for battery owners in 2026
Here are the main time-of-use tariffs available to UK homeowners with a home battery in 2026, with their key details as of June 2026:
The most widely used smart tariff for battery and EV owners. The 6-hour off-peak window overnight is enough to fully charge a 10kWh battery while also running an EV charger. Simple, predictable, and available across England, Scotland, and Wales. No exit fee.
Like Octopus Go but with a smart charging layer that can extend your off-peak window further when grid demand is low — potentially giving you additional cheap hours beyond the standard window. Particularly useful for households with both a battery and an EV. Requires a compatible smart charger.
A 7-hour off-peak window makes this particularly good for larger battery systems (20kWh+) that need more time to charge fully. The off-peak rate is slightly higher than Octopus Go, but the extra hour of cheap electricity can be valuable for high-consumption households.
Designed for households with solar and a battery. Import cheaply overnight, export at a high rate during peak hours — the battery acts as a two-way financial asset. The three-period structure (cheap, shoulder, expensive) requires careful management but offers the highest ceiling savings for solar-equipped homes.
Source: Octopus Energy, tariff details, June 2026. octopus.energy. EDF Energy, GoElectric tariff guide, 2026. edfenergy.com. Rates correct as of June 2026 and subject to change.
How the savings stack up: a direct comparison
Using a 10kWh ESME Power Tower on a full daily charge cycle, here is how savings compare across tariffs at July 2026 electricity rates:
| Tariff | Off-peak rate | Charge cost (10kWh) | Peak saving vs 26.11p | Est. annual saving |
|---|---|---|---|---|
| Octopus Go | 7p | 70p | £1.91/cycle | ~£697/yr |
| Intelligent Octopus Go | 7p | 70p | £1.91/cycle | ~£697/yr |
| EDF GoElectric 35 | 9p | 90p | £1.71/cycle | ~£624/yr |
| Standard variable (no TOU) | 26.11p | £2.61 | £0 | £0 |
Source: Calculations based on Ofgem July 2026 price cap rate of 26.11p per kWh and published tariff off-peak rates. Figures assume one full 10kWh charge cycle per day, 365 days per year. Actual results vary by usage and tariff availability.
What switching tariff is worth: a real example
How to choose the right tariff for your battery
The best tariff for your household depends on several factors beyond the headline off-peak rate. Here's how to think through the decision:
Match the off-peak window to your battery's charge time
A 10kWh battery drawing at 3.6kW needs roughly 3 hours to charge from flat. A 25kWh system needs 7 hours at the same rate. Make sure your chosen tariff's off-peak window is long enough to fully charge your battery every night. For larger systems, EDF GoElectric's 7-hour window may suit better than Octopus Go's 6-hour window.
Consider whether you have an EV
If you're charging both a battery and an EV overnight, you'll want a tariff with a long enough window to handle both, or a smart tariff like Intelligent Octopus Go that can extend the cheap window dynamically. Competing for overnight capacity between a battery and an EV on a short window means one or both may not fully charge.
If you have solar, prioritise export rates
Households with solar panels should factor export rates into their tariff comparison. Octopus Flux pays a high rate for electricity exported during peak hours — which, combined with a battery storing daytime solar generation for peak discharge, can significantly increase total return. Outgoing Octopus is also worth comparing if you have solar but don't need the full Flux structure.
Check exit fees before switching
Some fixed smart tariffs carry exit fees if you switch before the contract ends, typically £30 to £50 per fuel. Octopus Go is a variable smart tariff with no exit fee, giving you flexibility if better options emerge. If you're considering a fixed smart tariff, check the exit fee terms before committing.
Ask ESME before you switch
ESME's team advises on tariff selection as part of every installation and is available to existing customers considering a switch. We review your usage profile and battery size against current tariff options to recommend the best fit — so you switch once into the right deal rather than discovering a better option six months later.
Do you need a smart meter to switch? Yes. All time-of-use tariffs require a smart meter to record your half-hourly consumption. If you don't have one, your energy supplier will arrange installation at no cost. This usually takes 2 to 4 weeks, so factor this into your timeline if you're planning an imminent battery installation.
Smart tariff Q&A
The most commonly asked questions about smart tariffs and home battery savings, answered clearly.
For most UK homeowners with a home battery but no solar panels, Octopus Go is currently the most cost-effective option, offering 7p per kWh overnight from 11:30pm to 5:30am. For households with solar panels, Octopus Flux may offer higher overall returns by also paying a strong export rate. ESME recommends discussing your specific setup before switching.
Yes, and if you haven't already switched, doing so should be your first priority after installation. You can switch energy suppliers or tariffs at any time. If you're on a fixed tariff with exit fees, check whether the savings from switching outweigh the exit cost — at 7p vs 26p, they usually do within a few months.
At July 2026 rates, a 10kWh ESME Power Tower on Octopus Go saves approximately £697 per year compared to buying all electricity at the standard variable peak rate of 26.11p. A 25kWh system on the same tariff would save proportionally more. Actual savings depend on your usage patterns, how consistently the battery is fully cycled, and your specific tariff rate.
Yes. Smart tariffs like Octopus Go work entirely independently of solar. The battery charges from the grid during the cheap off-peak window and discharges during peak hours. No solar generation is required. This is the core of the ESME model — solar-free home battery storage powered by off-peak grid electricity.
Your savings increase. The financial benefit of a home battery on a smart tariff comes from the gap between the off-peak rate and the peak rate. As the peak rate rises with the price cap, that gap widens and your battery saves more per cycle automatically, without any change to your system or behaviour. This is one of the strongest arguments for investing in a battery now rather than waiting.
No. Your energy supplier has no connection to your battery hardware or the ESME app. You can switch supplier freely without affecting how your battery operates. The only change required is updating your charge schedule in the app to reflect the new tariff's off-peak window if it differs from your previous supplier's.
Ready to start saving with the right tariff?
ESME advises on tariff selection as part of every installation and for existing customers looking to optimise. Find out how much you could save at today's rates.
Calculate your savingsSources
- 1. Ofgem, 'Smart tariffs and smart meters', 2024. ofgem.gov.uk
- 2. Octopus Energy, 'Octopus Go and Intelligent Octopus Go tariff details', June 2026. octopus.energy
- 3. EDF Energy, 'GoElectric 35 tariff guide', 2026. edfenergy.com
- 4. Ofgem, July 2026 energy price cap — electricity unit rate 26.11p per kWh. ofgem.gov.uk
- 5. ESME Energy, product specifications and customer savings data, 2025. esme.energy