UK Smart Export Guarantee Calculator

Calculate your SEG export income, self-consumption savings, and total annual benefit. Compare all major UK suppliers side by side and find the best rate for your system.

Solar system details

System size?

Annual generation?

kWh/yr

Self-consumption rate?

SEG supplier?

Your electricity rate?

p/kWh

Smart Export Guarantee earnings

£1055.70/year total benefit

Annual export to grid3,510 kWh/yr

Annual self-use1,890 kWh/yr

SEG income (15p)£526.50/yr

Self-consumption savings (28p)£529.20/yr

Total annual benefit£1055.70/yr

25-year total earnings£26,392

Est. system cost£9,000

Estimated payback8.5 yrs

SEG supplier comparison

Supplier	Rate	Annual income	Notes
Octopus OutgoingBEST	15p/kWh	£526.50/yr	Best fixed rate. No minimum export requirement.
Octopus Flux export	12p/kWh	£421.20/yr	Variable agile rate. Higher on some days, lower on others. Average ~12p.
E.ON Next	5.5p/kWh	£193.05/yr	Fixed 5.5p/kWh. No export meter required.
OVO Energy	4p/kWh	£140.40/yr	Fixed 4p/kWh. Requires smart meter.
British Gas	3.2p/kWh	£112.32/yr	Fixed 3.2p/kWh. All Hive customers eligible.
EDF Energy	3p/kWh	£105.30/yr	Fixed 3p/kWh. EDF customers only.

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How to Use This Calculator

Enter your solar system details

Start with your system size in kW and estimated annual generation. If you don't know your actual generation, use 900 kWh per kW as a rough UK average (higher in the South of England, lower in Scotland). Your MCS certificate or installer quote should include a projected annual yield figure. Enter your self-consumption rate — without a battery this is typically 20–40%; with a battery you can reach 60–80%.

Select your SEG supplier

Choose your current Smart Export Guarantee supplier from the dropdown. Rates vary from 3p/kWh (EDF) to 15p/kWh (Octopus Outgoing). You can switch SEG suppliers independently of your electricity import tariff — you don't have to buy and sell from the same company. The comparison table shows what you'd earn with each supplier for your specific export volume.

Read the results

The calculator separates total benefit into SEG export income (what you earn selling to the grid) and self-consumption savings (what you avoid paying by using your own solar). Both matter: at 28p/kWh import rate, self-consumption is often worth more than export income even with a competitive SEG rate.

The Formula

Export kWh = Annual Generation × (1 − Self-consumption %) Self-use kWh = Annual Generation × Self-consumption % SEG Income (£) = Export kWh × SEG Rate (£/kWh) Self-consumption Savings (£) = Self-use kWh × Electricity Import Rate (£/kWh) Total Annual Benefit = SEG Income + Self-consumption Savings 25-year Projection = Total Annual Benefit × 25 System Cost = System kW × £1,500/kW (UK installed average 2026) Payback = System Cost ÷ Total Annual Benefit

The 25-year projection assumes flat rates — in practice, electricity prices tend to rise over time, which improves the projection. Conversely, SEG rates can change when you switch tariff at renewal. Octopus Outgoing and similar competitive rates are subject to periodic review, though fixed-term options are available.

Example

Sarah — 6kW system with battery in Surrey, Octopus Outgoing SEG

Sarah has a 6kW solar system with a 10kWh battery in Surrey, generating 5,400 kWh/year. The battery raises her self-consumption to 70%. She's on Octopus Outgoing SEG at 15p/kWh and pays 28p/kWh for imports.

System6kW solar + 10kWh battery

Annual generation5,400 kWh/yr

Self-consumption70%

SEG rateOctopus Outgoing 15p/kWh

Import rate28p/kWh

Result

Export to grid1,620 kWh/yr

SEG income£243/yr

Self-consumption savings£1,058/yr

Total annual benefit£1,301/yr

25-year total£32,525

Est. system cost~£9,000 (6kW)

Payback~6.9 years

Sarah's battery dramatically shifts the economics. Self-consumption savings at 28p/kWh dwarf SEG income at 15p — proving that maximising self-use is more valuable than maximising export. Without the battery at 35% self-consumption, total benefit drops to ~£860/yr and payback extends to ~10.5 years. The battery's extra £440/year benefit helps justify its additional cost.

FAQ

What is the Smart Export Guarantee (SEG) and how does it work? ▼

The Smart Export Guarantee (SEG) replaced the Feed-in Tariff in January 2020. It requires large energy suppliers (with 150,000+ customers) to offer a tariff for surplus solar electricity you export to the grid. Unlike the old FiT, there is no government-set rate — suppliers compete on what they'll pay, ranging from 3p/kWh (EDF) to 15p/kWh (Octopus Outgoing) as of 2026. You must have a smart meter or half-hourly export meter to receive SEG payments. Any installation of 5MW or less with an MCS certificate is eligible. You can switch SEG suppliers at any time without changing your electricity import tariff.

Is Octopus Outgoing the best SEG rate in 2026? ▼

As of 2026, Octopus Outgoing at 15p/kWh is the highest fixed SEG rate from a major supplier. Octopus Flux export can pay more on high-demand days (sometimes 20p+) but averages around 12p/kWh. For predictable income, the 15p fixed rate is the best option. E.ON Next at 5.5p is the next-best fixed rate for non-Octopus customers. Rates change periodically — always check each supplier's current offer before signing up. The comparison table in the calculator shows current rates and annual income for your specific export volume.

Does a battery storage system improve SEG earnings? ▼

A battery changes the SEG economics significantly. More self-consumption means less export, so SEG income actually decreases with a battery. However, the energy you self-consume is worth 28p/kWh (import rate) vs only 15p/kWh (SEG rate) — so using it yourself is 87% more valuable than selling it. A battery also enables "time-shifting": charge from solar during the day, discharge in the evening, thereby avoiding expensive peak grid electricity. The net result is that a battery typically improves overall financial returns even though it reduces SEG income specifically.

What self-consumption rate can I realistically achieve in the UK? ▼

Without a battery, UK self-consumption is typically 25–40% depending on home occupancy, lifestyle, and whether you have high daytime loads (EV, heat pump, dishwasher run during the day). A work-from-home household can achieve 40%+ naturally. With a 5–10 kWh battery, self-consumption rises to 55–75%. With a larger battery (15+ kWh) or very high loads (EV + heat pump), you can reach 80–85%. 100% self-consumption is rarely achievable in the UK — there will always be surplus on long summer days.

Can I switch SEG suppliers without changing my electricity tariff? ▼

Yes — the SEG is completely separate from your electricity import tariff. You can export with Octopus Outgoing while importing from British Gas, for example. However, some suppliers (particularly Octopus) offer combined tariffs (like Octopus Flux) where the import and export rates are linked and optimised together, which can provide better overall economics than mixing suppliers. If you're happy with your import supplier, switching just your SEG to Octopus Outgoing is a straightforward process and typically takes 2–4 weeks. You'll need to provide your smart meter MPAN and a recent generation reading.

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