Battery storage strategies

Home batteries are transforming the economics of domestic energy, particularly when paired with Octopus’s time-of-use tariffs. The fundamental principle is beautifully simple: charge when electricity is cheap, discharge when it’s expensive. The details of how you do that depend on your setup and which tariff you’re on.

Why batteries love time-of-use tariffs

On a flat-rate tariff, a battery doesn’t make much financial sense for grid-only households. You’d be charging and discharging at roughly the same price, losing a bit to inefficiency each cycle. The maths just doesn’t work.

Time-of-use tariffs change everything. When there’s a genuine price difference between cheap and expensive periods, every cycle of your battery captures that spread as profit. The bigger the spread, the better the return. Octopus’s tariffs create some of the largest spreads available to domestic customers.

Strategy 1: Solar + battery on Flux

This is the strategy Flux was specifically designed for. During the day, your solar panels charge your battery. In the evening peak window (4pm-7pm), you export stored energy at Flux’s premium export rate while simultaneously avoiding the higher peak import rate.

The beauty of Flux is that both the import and export tariffs have time-of-use bands that align perfectly with solar generation patterns. You’re rewarded twice over: lower rates when you’re importing (overnight and midday) and higher rates when you’re exporting (evening peak).

A typical day on Flux with solar and a battery looks like this: overnight you import at the low rate to cover base load. From mid-morning, solar takes over and starts filling the battery. By early afternoon the battery is full and any excess exports at the midday rate. At 4pm, you switch to exporting from the battery at the premium rate. By 7pm the battery is partially or fully discharged, and you go back to grid import at the lower evening rate.

Strategy 2: Grid + battery on Agile

No solar panels? A battery on Agile can still work. Agile’s half-hourly pricing regularly dips below 10p overnight and occasionally goes negative (they literally pay you to use electricity). Meanwhile, evening peak rates frequently hit 30-40p and sometimes higher.

The strategy is straightforward: schedule your battery to charge during the cheapest overnight slots and discharge during the expensive evening period. The spread can be 20-30p per kWh on a good day. With a 10kWh battery cycling daily, that’s £2-3 per day in savings, or potentially £700-1,000 per year.

The catch is that Agile prices vary. Some days the spread is huge, other days it’s modest. You need to be comfortable with variability, and ideally your inverter or battery management system should be smart enough to respond to price signals automatically.

Strategy 3: Solar + grid + battery hybrid

This is the most flexible approach and often the most profitable. You have solar panels generating during the day, a battery that charges from both solar and cheap grid electricity, and a time-of-use tariff that rewards you for exporting at the right times.

On a summer day, solar alone might fill your battery by noon. On a winter day, solar might only contribute 20-30% of a full charge, so you top up from the grid overnight at the cheap rate. Either way, your battery is full when you need it for the evening peak.

This hybrid approach works on Flux, Agile or even Go (if you have an EV and want to combine cheap overnight charging with battery arbitrage).

Popular battery brands

The UK home battery market has settled around a handful of well-established brands:

• Tesla Powerwall 3: 13.5 kWh with a built-in hybrid inverter. The latest version has a higher continuous power output (11 kW) and handles solar input directly. Expensive but feature-rich, and now compatible with Intelligent Octopus Flux.
• GivEnergy: Modular systems in 2.6 kWh and 5.2 kWh units. Very popular in the UK enthusiast community with excellent inverter integration and local support. One of the first brands to work with Intelligent Octopus Flux.
• Huawei Luna 2000: 5-15 kWh (modular in 5 kWh blocks). Designed for Huawei inverters. Competitive pricing.
• Fox ESS: Solid mid-range choice with good inverter-battery integration, also compatible with Intelligent Octopus Flux.
• Growatt: Budget-friendly option with reasonable performance. Growing market share in the UK.

Most of these come in sizes from 5 kWh up to 13.5 kWh, with modular systems allowing you to add capacity later. A 5 kWh battery handles a few hours of average household consumption. A 10 kWh battery comfortably covers a full evening and overnight period for most homes.

Does a battery pay for itself?

This is the question everyone asks, and the honest answer is: it depends entirely on how you use it.

A 5 kWh battery typically costs £3,500-5,500 installed (or £4,500-6,000 as a standalone retrofit). A 10 kWh system runs £5,500-7,000 when installed alongside solar panels, or £7,000-10,000 as a standalone addition. Costs have risen slightly in recent years, though the 0% VAT on battery installations (in effect until March 2027) helps offset that. Most lithium batteries are warrantied for 10 years or 6,000-10,000 cycles (whichever comes first), so you’ve got a long window to recoup the investment.

On Flux with solar, a 10 kWh battery capturing a 15-20p per kWh spread daily generates roughly £550-730 per year in value. That puts payback at around 8-12 years, depending on what you paid. On Agile without solar, the maths are similar if the daily spread averages 20p+ consistently.

Without a time-of-use tariff, payback extends to 15+ years for grid-only households. The tariff pairing is what makes the investment viable. We dig into the full financial picture in our payback calculations guide, and you can check current rates with the tariff comparison tool.

Charge scheduling

How you control your battery charging matters. There are two main approaches:

Inverter app scheduling is the most common. GivEnergy, Tesla, Huawei and Fox ESS all have their own apps where you set charge and discharge windows. You tell the battery: charge between midnight and 5am, discharge between 4pm and 9pm, hold at other times. Simple and reliable.

Octopus integration goes a step further. Intelligent Octopus Flux lets Octopus directly control your battery charging and discharging, optimising around grid demand and price signals. It currently works with GivEnergy, Tesla, SolarEdge, Enphase and Fox ESS systems. For Agile customers, the Octopus app can communicate with certain inverters to optimise charging based on tomorrow’s prices. Both approaches are more hands-off but require compatible hardware and a bit of initial setup.

The enthusiast community has also built third-party tools that sit between Octopus’s API and various inverters, enabling automatic price-optimised scheduling even where official integration doesn’t exist. GivEnergy owners in particular benefit from a thriving community of scripts and tools.