Products & compliance
Solar battery storage: how home batteries work
A home battery stores electricity — from your solar panels or from cheap off-peak tariffs — so you can use it when you need it instead of buying from the grid. It fixes solar's timing problem: generation peaks at midday, but most homes use most electricity in the evening.This guide explains how battery storage works and what it changes. For the plug-in-specific case, see plug-in solar with battery storage.
Written and edited by Christopher Panteli
Christopher is the founder and editor of MyPlugInSolar. He oversees the site’s research standards, data tools and editorial process. He is not an electrician or solar installer, and specialist technical claims are sourced from official documentation or reviewed by appropriately qualified professionals.
How a solar battery works
During the day, surplus solar that your home isn't using charges the battery instead of exporting to the grid. In the evening, the battery discharges to cover your usage before you buy any grid electricity. Some setups also charge from the grid overnight on cheap time-of-use tariffs and discharge at peak times — useful even without solar. The economics rest on the gap between what exported electricity earns (often little — see can plug-in solar export to the grid?) and what imported electricity costs.
The numbers that matter
Match capacity to your evening and overnight usage — your daytime base load thinking, applied to the other half of the day. An oversized battery spends money storing energy you never use; an undersized one runs flat before bedtime.
| Specification | Unit | What it tells you |
|---|---|---|
| Capacity | kWh | How much energy it stores — how long it can cover your usage |
| Power | kW | How fast it can charge/discharge — what loads it can cover at once |
| Depth of discharge | % | How much of the capacity is actually usable |
| Cycle life / warranty | cycles or years | How long the battery is guaranteed to keep performing |
AC-coupled vs DC-coupled
An AC-coupled battery has its own inverter and connects to your home's AC wiring — it can be retrofitted to any existing solar system (or no solar at all). A DC-coupled battery shares a hybrid inverter with the panels, which is more efficient for storing solar but usually means designing the system together from the start. Grid-tie behaviour and protections like anti-islanding apply either way — see grid-tie inverters.
Safety and compliance
Where plug-in and balcony storage fit
In the EU, balcony-solar storage products (batteries that sit between plug-in panels and the socket, such as Zendure's SolarFlow line or EcoFlow's PowerStream pairings — see our products tracker) have become popular. In the UK the position is stricter: plug-in solar is not yet legal to sell, supply or use, and the Government consultation that closed on 30 June 2026 explicitly excluded batteries from its scope. So even if plug-in solar is permitted, plug-in battery storage would remain a separate, unresolved question. We don't publish battery prices or savings promises — model your own numbers with the calculator and treat storage as a second, separate investment decision.
Frequently asked questions
- Is solar battery storage worth it?
- It depends on the gap between your import price and export earnings, how much surplus your solar produces, and the battery's cost and lifespan. A battery only pays back through energy it actually shifts — size it to your evening usage and do the arithmetic before buying. We don't publish one-size-fits-all payback claims.
- Can I add a battery to an existing solar system?
- Usually yes, with an AC-coupled battery, which has its own inverter and doesn't disturb the existing panels. DC-coupled systems share a hybrid inverter and are normally designed in from the start. Either way it is professional fixed-wiring work.
- Do balcony solar batteries work in the UK?
- Products like Zendure SolarFlow exist and are popular in the EU, but plug-in solar is not yet legal to use in the UK, and batteries were explicitly outside the scope of the Government's plug-in solar consultation — so plug-in storage remains unresolved here.
Sources
- 1. Connecting generation and storage (G98/G99) — Energy Networks Association
- 2. BS 7671 Requirements for Electrical Installations (IET Wiring Regulations) — Institution of Engineering and Technology
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