Why commercial SEG rates are lower than the headline tariffs — and the three routes that pay more
Published 2026-09-16 · 6 minute read · By Commercial Solar Finance editorial team
The research question: a comparison site says the best export rate is 20p a unit, so why is our 300kWp warehouse array being offered 4p? Because the 20p was never for you. Rates checked on 16 September 2026.
Export tariff league tables are written for households. On 16 September 2026 the highest rates we could verify on supplier pages were OVO's SEG Install Exclusive at up to 20p/kWh and Octopus's Prime Outgoing at 16p/kWh in the 4pm–7pm window. Both carry conditions that a commercial array cannot meet or does not want. The commercial SEG rates page lists every figure we verified; this piece explains why the commercial number is so different.
Condition one: the 30kW cap
OVO's 20p (and its 15p solar-only and 12p Beyond Exclusive rates) apply to installations under 30kW, and the 20p and 15p rates only where OVO installed the system. A 100–500kWp commercial roof is ten to fifty times too large. What OVO offers a business at that scale is its any-supplier SEG at 4p/kWh, available up to the scheme's 5MW ceiling.
Condition two: be our import customer
Octopus's Outgoing tariffs — 12p flat, or 16p peak and 9p off-peak on Prime — are for sites whose electricity import is supplied by Octopus. For a business on a fixed commercial contract elsewhere, moving the import supply is a procurement decision with its own price, not a free switch. Where it can be done, the flat 12p is the best open commercial export rate we could verify.
Condition three: the time-of-export shape
Prime Outgoing pays 16p between 4pm and 7pm and 9p otherwise. A commercial array exports most in the middle of the day, when the site is running and the sun is highest, so without storage it earns the 9p most of the time. The 16p rewards a battery that shifts export into the evening — a design decision with a capital cost, not a tariff you simply sign up to.
What a 300kWp warehouse actually earns
| Assumption | At 4p/kWh | At 12p/kWh | Self-consumed at 25p/kWh avoided |
|---|---|---|---|
| 300kWp, 950 kWh/kWp = 285,000 kWh a year; 35% exported (99,750 kWh) | £3,990 | £11,970 | 185,250 kWh × 25p = £46,313 |
Even on the better tariff, export is worth a quarter of what self-consumption is worth. The design rule that follows is the one every commercial installer knows and every comparison article ignores: size to daytime demand, then export the residue, and treat the export rate as a rounding item rather than the business case.
The three routes that pay more than the SEG
- Private-wire or sleeved PPA with a neighbour: sell the surplus to the site next door at a price between the SEG rate and their grid tariff; needs a physical connection or a supplier to sleeve it.
- Aggregator export contract with flexibility: an aggregator buys your export and, with a battery, sells grid services on top; typical for 1MW and above.
- Merchant export above 5MW: the SEG stops at 5MW, so ground-mount and large rooftop schemes sell under a power purchase agreement priced off wholesale — see power purchase agreements.
Read next: the verified commercial SEG rates table and our battery storage finance guide for the evening-export case.
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