Battery Storage vs Exporting Solar
Store your excess solar energy or sell it back to the grid? We compare the real-world numbers so you can see which strategy — or combination — pays more for your home.
Quick answer: store vs export — who wins?
In most cases, storing solar energy in a battery and using it yourself saves significantly more than exporting it. The maths is straightforward: grid electricity costs 24–28p per kWh, while the best SEG export rates pay just 4–15p per kWh. Every unit you store and use yourself avoids buying one at full price.
However, exporting can still be the better move in certain situations — particularly if you have a small system, low evening usage, or access to a high-paying export tariff. The answer depends on your system size, usage pattern, and tariff.
How SEG and export tariffs work
Under the Smart Export Guarantee (SEG), energy suppliers with 150,000+ customers must offer you a payment for every kWh of solar electricity you export to the grid. Rates vary widely — from as low as 1p/kWh on basic tariffs to 15p/kWh or more on agile/smart tariffs.
Fixed-rate SEG tariffs pay a set price per kWh regardless of time of day. Agile export tariffs (like Octopus Outgoing) pay variable rates that can spike during peak demand — occasionally exceeding 30p/kWh — but average much lower. Your export income depends on which tariff you choose and when your system generates surplus.
- Basic fixed SEG: 4–6p per kWh (e.g. EDF, British Gas)
- Mid-range fixed SEG: 8–12p per kWh (e.g. Octopus Fixed Export)
- Agile/variable export: 1–30p+ per kWh depending on time (e.g. Octopus Agile Outgoing)
- You need an MCS-certified installation and a smart meter to claim SEG payments
When battery storage beats exporting
A battery delivers the best return when the gap between what you'd pay for grid electricity and what you'd earn from exporting is large. These scenarios strongly favour storing:
- High evening usage — families who use most electricity between 4–9pm benefit most, as stored solar replaces the most expensive grid units
- Smart tariff users — charging a battery overnight at 7–10p/kWh and discharging at 24–28p during the day creates savings even without solar generation
- Low export rates — if your SEG tariff pays 4–6p/kWh, you're giving away energy worth 24–28p to you. Storing makes 4–6× more sense
- Larger systems (4 kW+) — bigger systems generate more surplus than you can use in real time, so a battery captures what would otherwise be exported cheaply
- Time-of-use tariffs — batteries let you shift consumption to off-peak hours, stacking solar savings with tariff savings
When exporting beats a battery
Exporting can be the smarter financial choice in a few specific situations where the cost of a battery doesn't justify the extra savings:
- Small solar systems (1–2 kW) — there's less surplus to store, so a £4,000+ battery takes much longer to pay back
- Low electricity usage — if you're out all day and use little in the evening, there's less expensive grid electricity for a battery to displace
- High export tariff — if you're earning 12–15p/kWh on a good fixed SEG, the gap between export income and self-use savings narrows considerably
- Short-term ownership — if you plan to move within 3–5 years, the battery may not pay back before you sell. Export income starts immediately with no capital outlay
- Budget constraints — the £0 upfront cost of exporting vs £3,500–£9,000 for a battery is a real consideration
Hybrid strategy: store some, export some
Most battery systems automatically do both — and that's usually the optimal approach. The battery charges first from your solar surplus, and once full, any additional generation is exported to the grid for SEG income.
With a well-sized battery (matching your evening usage, typically 5–10 kWh), you maximise self-consumption during expensive hours while still earning export income from any genuine surplus. On long summer days, a 4 kW system can generate 20+ kWh — far more than most batteries hold — so you'll naturally export the excess.
Smart battery systems like GivEnergy and Tesla Powerwall can be programmed to optimise this split automatically, factoring in your tariff rates, weather forecasts, and usage patterns.
FAQs: batteries and exporting
Common questions about how batteries and export payments interact:
- Do I still get SEG with a battery? — Yes. Any electricity your battery doesn't absorb is exported and earns SEG payments as normal. A battery doesn't disqualify you
- Can I export from my battery? — On most tariffs, yes. Some smart tariffs pay you to discharge stored energy during peak grid demand. Check your supplier's terms
- What size battery maximises savings? — Match your battery to your evening/overnight usage. For most homes that's 5–10 kWh. Oversizing adds cost without proportional benefit
- Does a battery reduce my export income? — Yes, because you're using more of your solar generation yourself. But the self-use savings (24–28p/kWh) far exceed lost export income (4–15p/kWh) in most cases
- Can I switch SEG tariff later? — Yes. You can change SEG supplier without affecting your solar or battery setup. Shop around annually for the best rate
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