If you already have solar panels — or you're planning to get them — the question of whether to add battery storage is one of the most common we hear from Sussex homeowners. The honest answer is: it depends. But in 2025, the numbers are looking better than ever for many households.

This guide cuts through the marketing and gives you a realistic picture of what battery storage actually costs, what it saves, and when it genuinely makes financial sense.

What Does Solar Battery Storage Actually Do?

Without a battery, your solar panels generate electricity during daylight hours. Any surplus you don't use immediately gets exported to the grid — typically at 4–15p per kWh via the Smart Export Guarantee (SEG). But you then buy electricity back from the grid in the evening at 24–35p per kWh.

A battery stores that surplus solar energy so you can use it later — in the evening, overnight, or during cloudy periods. This increases your self-consumption rate (the proportion of your solar generation you actually use yourself) from a typical 30–40% without storage to 70–90% with a well-sized battery.

The Real Numbers: Battery Storage Costs in 2025

Note: These are retrofit costs — adding a battery to an existing solar system. If you're installing solar and battery together, the combined cost is usually lower than buying them separately.

Annual Savings: What Can You Realistically Expect?

The payback period for a standalone battery retrofit is longer than for solar panels alone. However, if you're on a time-of-use tariff like Octopus Agile or Intelligent Octopus, you can also charge your battery from cheap overnight grid electricity (sometimes as low as 7–10p/kWh) and discharge it during peak periods — which can significantly improve the economics.

When Battery Storage Makes the Most Sense

When Battery Storage Might Not Be Worth It (Yet)

• You're at home all day: If you already use most of your solar generation directly, a battery adds less value
• You have a very small solar system: A 2–3kWp system may not generate enough surplus to justify a battery
• You're on a flat-rate tariff: The savings from avoiding peak rates are lower if you pay the same rate all day
• Budget is tight: Solar panels alone offer a better return on investment — add a battery later when prices fall further

Our Verdict

For most Sussex homeowners installing solar in 2025, we recommend at least considering battery storage — particularly if you're on or planning to switch to a time-of-use tariff, or if you have an EV. The economics are improving year on year as battery prices continue to fall.

If you already have solar and are thinking about retrofitting a battery, the decision is more nuanced. We'd recommend getting a proper assessment of your current self-consumption rate and energy usage patterns before committing.

Green Earth Sussex installs battery storage systems and retrofits across all of East and West Sussex. Visit our Solar PV Installers page or call us on 01273 076860 for a free assessment.