What Solar Battery Storage Does
Without a battery, any solar electricity you generate but don’t use immediately is exported to the grid. You earn a few pence per kWh through the Smart Export Guarantee (SEG), but you lose the real value of that electricity.
With a battery, excess solar is stored and used in the evening when your usage peaks. Instead of paying 24p/kWh to buy electricity from the grid, you use your stored solar electricity for free. The value shift is significant: instead of exporting at 4–8p/kWh and buying back at 24p/kWh, you use your own electricity directly.
Daytime generation powers your home first, then charges a battery for the evening; only the surplus is exported for Smart Export Guarantee income.
Sigenergy vs EcoFlow: Our Recommended Systems
Sigenergy — A fully integrated inverter and battery platform. The Sigenergy system combines the solar inverter, battery inverter, and EV charger into a single elegant unit. Key features include AI-powered energy management, modular battery expansion from 5 to 30 kWh, and best-in-class round-trip efficiency. Ideal for homes wanting a clean, future-proof installation.
EcoFlow — Known for innovation and reliability, EcoFlow’s home battery systems offer excellent cycle life (6,000+ cycles), flexible capacity options, and smart home integration. Their whole-home backup capability means critical appliances keep running during power cuts.
Both brands offer 10+ year warranties and are designed for the UK climate. We recommend the best fit based on your specific requirements during the design phase.
The Financial Case
A 10 kWh battery system costs £4,000–£5,500 installed. To calculate your savings:
- Daily self-consumption boost: A battery typically increases your self-consumption from 30–40% (solar only) to 70–80% (solar + battery).
- Value per kWh shifted: Each kWh you use from the battery instead of the grid saves you roughly 16–20p (the difference between grid import price and SEG export rate).
- Annual saving: For a 4 kWp system, this typically adds £400–£600 per year in additional savings.
Payback period for the battery element alone: 7–12 years. But factor in rising electricity prices (which increase savings) and the backup power benefit, and the investment makes strong sense.
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Time-of-Use Tariffs
Some electricity tariffs offer cheaper rates at night (e.g., Octopus Go, Agile). With a battery, you can charge at night when rates are as low as 7–10p/kWh and discharge during peak hours when rates can exceed 30p/kWh.
This “tariff arbitrage” works alongside solar generation and can add another £150–£300/year in savings. Our Sigenergy and EcoFlow systems both support smart tariff integration.
Battery Payback: A Worked Example
A home battery earns its keep in two ways: storing your own free solar for the evening, and charging from the grid during cheap off-peak windows to use at peak times. Here is a realistic worked example for a Midlands home with a 4.5kWp array and a 10kWh battery.
- Solar self-use gain: without a battery, a typical home exports 50–60% of its solar because generation peaks midday when nobody is home. A battery captures that surplus, lifting self-consumption from ~40% to ~80% and saving roughly £350–£450 a year in avoided imports.
- Off-peak arbitrage: on a time-of-use tariff you can charge the battery at ~7p/kWh overnight and avoid buying at ~24p+ during the peak, worth a further £150–£300 a year depending on usage.
- Combined saving: roughly £500–£700 a year, giving a payback of around 8–12 years on a battery costing £3,500–£6,000 — comfortably inside the 10–15 year warranty on quality units like the Sigenergy and EcoFlow systems we install.
A battery also gives you resilience during power cuts (with the right inverter) and lets a heat pump lean on stored cheap power in the evening. The economics are strongest when you pair the battery with both solar and a heat pump, so all three assets work together rather than in isolation.
Frequently asked questions
For most solar homes, yes. A battery lifts self-consumption from 30–40% to 70–80% and typically adds £400–£600 a year in savings for a 4kWp system, with the battery element paying back in about 7–12 years.
5kWh suits smaller households, 10kWh is the sweet spot for most homes, and 13–15kWh suits high-usage homes with a heat pump and EV. We size it to your evening demand and solar output.
Around 7–12 years for the battery on its own, improving as electricity prices rise and if you use a time-of-use tariff to charge cheaply overnight and discharge at peak.
Flux-style and time-of-use tariffs (such as Octopus Flux or Agile) reward solar-and-battery homes with cheap overnight import and premium export windows. Our Sigenergy and EcoFlow systems support smart tariff integration.
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