Self-Consumption vs Export Calculator
See how a battery shifts solar from export to self-use
Self-consumption vs export
See how adding a battery shifts your solar from export to self-use. Based on a typical 4 kW system (9 x 450W panels) generating 4,200 kWh/yr.
Self-used
1,680 kWh
Worth ~£412/yr
Exported
2,520 kWh
Earns ~£302/yr
Self-consumed electricity saves you the full import rate (24.5p/kWh). Exported electricity earns only the export rate (12p/kWh) — less than half. That is why batteries make such a difference.
How this works
Without a battery, a typical UK household directly uses about 40% of the electricity their solar panels generate. The other 60% is exported to the grid because generation peaks at midday when nobody is home.
A battery stores surplus daytime generation for use in the evening. A 5 kWh battery raises self-consumption to around 60%. A 10 kWh battery reaches 75-80%.
Self-consumed electricity saves you the full import rate (24.5p/kWh). Exported electricity only earns the SEG rate (typically 12p/kWh). The difference is why batteries make such a big financial impact.
Things to consider
- •Returns diminish above 10-15 kWh for most households — oversizing the battery does not pay back.
- •Your self-consumption ratio depends on your evening usage pattern. EV charging at home dramatically changes the maths.
- •Winter months generate far less, so a larger battery has less to store — size for summer surplus, not winter scarcity.
- •Battery round-trip efficiency is around 90%, meaning you lose 10% of stored energy when discharging.
Dig deeper
Solar Battery Storage: Complete UK Guide 2026
Everything you need to know about adding battery storage to a UK solar installation — types, sizing, costs, and which products are worth considering in 2026.
Battery Sizing Sweet Spot: How Big Is Big Enough?
How to choose the right battery size for your UK solar system. The sweet spot between too small, too big, and just right based on your consumption patterns.
Smart Export Guarantee (SEG) Explained
How the Smart Export Guarantee works in the UK, which suppliers pay the best SEG rates, and how to maximise your solar export income in 2026.
Adding a Battery to Existing Solar: What's Involved
How to add battery storage to an existing solar panel system. Compatibility, costs, installation options, and what to ask your installer before committing.
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