Smart Export Guarantee for office solar

Eligibility requirements:

For a typical 280 kWp office solar system generating 258,000 kWh/year at 78% self-consumption, exported volume is around 57,000 kWh/year. At a 10p/kWh SEG tariff, that's £5,700/year of additional revenue.

SEG revenue typically contributes 5-10% of total annual benefit on office solar installations — small relative to the avoided-cost economics from self-consumption, but a useful contribution to overall payback. We handle SEG registration as part of the commissioning process.

SEG rates by supplier: 2026 comparison

SEG tariffs are set independently by each obligated supplier and can change with notice. The best offers for commercial systems in 2026:

Octopus Outgoing Agile

Variable rate tracking wholesale half-hourly prices. Average 10-15p/kWh in peak periods, potentially negative during oversupply. Best for buildings with flexibility to shift load. Requires SMETS2 smart meter with half-hourly export capability.

Octopus Outgoing Fixed

Fixed ~9p/kWh regardless of time. Predictable revenue, simpler financial modelling. Best for buildings without flexible load management.

E.ON Next Export Exclusive

Fixed ~10p/kWh for E.ON Next import customers. Competitive rate with no time-of-use complexity. Requires E.ON Next import contract.

OVO / SSE SEG tariff

Fixed ~8p/kWh. Straightforward registration, quarterly payments. Available to OVO and legacy SSE business customers.

Rates correct Q2 2026. SEG suppliers review rates periodically — check directly with suppliers for current offers before signing.

How SEG interacts with PPAs and other funding routes

Under a power purchase agreement (PPA), the solar asset is owned by the PPA provider, not the building owner. This means the PPA provider registers for SEG, not the building owner — and SEG revenue either flows to the PPA provider (reducing the tariff they can offer you) or is passed through as a lower electricity supply price. When comparing cash purchase against PPA, always ask your PPA provider how they handle SEG — it affects the tariff comparison by 0.5-1.5p/kWh.

For owned systems financed via asset finance or operating lease, the building owner registers for SEG and receives the export payments directly. SEG income is taxable as trading income for limited companies (subject to corporation tax) and as business income for sole traders and partnerships.

SEG does not interact with AIA, Full Expensing, or Salix PSDS grants — these are capital-side reliefs, while SEG is an ongoing revenue stream. You can claim all applicable capital reliefs and receive SEG export payments simultaneously.

SEG and battery storage: what you need to know

Adding battery storage affects SEG revenue in two ways. First, battery storage captures surplus generation that would otherwise be exported, reducing export volume and therefore SEG receipts. A 280 kWp system with no battery might export 57,000 kWh/year; the same system with 200 kWh battery might export only 18,000 kWh/year. At 10p/kWh, the SEG revenue difference is £3,900/year.

This reduced SEG revenue is more than offset by the additional bill savings from the battery — which captures solar at roughly the same value as avoided grid cost (28-32p/kWh), versus the 9-12p/kWh export rate. The net NPV of adding battery storage is positive on most sites where the avoided-import tariff exceeds the SEG export tariff by 2× or more — which is currently always the case.

HMRC's position on battery storage eligibility for SEG: systems that include battery must still demonstrate that the battery is being charged primarily from solar generation (not grid) to remain eligible. Smart inverter settings and monitoring logs are the evidence of record for this. We configure inverter settings and provide monitoring access as part of the commissioning handover.

SEG registration: the process

1. MCS commissioning certificate: Required before SEG application. Issued by the installing contractor (us) on commissioning completion. Delivered as part of our standard handover pack.
2. SMETS2 smart meter: Required for half-hourly export metering. Must be installed by the DNO or distribution-connected operator before SEG registration. We coordinate smart meter installation with the relevant energy supplier during the install programme.
3. Application to chosen SEG supplier: Application form plus MCS certificate number plus smart meter serial number. Processing time typically 2-4 weeks.
4. Export data submission: SMETS2 meters transmit half-hourly export data automatically. SEG payments are made quarterly by BACS — no ongoing manual submission required.