The Smart Export Guarantee, Power Purchase Agreements, and the emerging flexibility market -- a practical account of the export income options available to a commercial on-site generator in the UK.
A commercial building with on-site generation has three routes to income from electricity it cannot use itself: the Smart Export Guarantee (SEG), a Power Purchase Agreement (PPA), and participation in flexibility and balancing services. Understanding the difference between them -- and which applies to a given installation -- is a practical prerequisite for the financial model.
The Smart Export Guarantee replaced the Feed-in Tariff for new installations from January 2020. It requires licensed electricity suppliers with more than 150,000 customers to offer an export tariff to generators with eligible installations up to 5 MW.
The SEG rate is not fixed -- each supplier sets its own rate, and rates vary from approximately 3p to 15p/kWh depending on the supplier and tariff product. Some SEG tariffs are flat; others are time-variable, paying more during peak demand periods. Time-variable SEG tariffs interact with AI-managed storage: the storage system can schedule export for the highest-rate periods, materially increasing the export income per kWh generated.
There is no minimum rate under the SEG framework. Generators should compare available rates before selecting a supplier.
A Power Purchase Agreement (PPA) is a direct contract between the generator and a buyer -- typically an energy retailer, an aggregator, or a large corporate buyer -- for the purchase of generated electricity at an agreed price. PPAs can be structured as fixed-price, index-linked, or floor-and-collar contracts, and typically run for 5--15 years.
For installations above approximately 500 kW, a PPA is often preferable to the SEG because it provides price certainty and can be structured to capture the full wholesale value of the generation rather than a retailer's margin-adjusted export rate.
For installations below 500 kW, the administrative cost of a bespoke PPA is generally not justified. The SEG or a virtual PPA (a financial contract that does not require physical electricity delivery) is more practical.
National Grid ESO operates a range of flexibility and balancing services that commercial generators and storage assets can participate in. The most accessible for small commercial installations are the Demand Flexibility Service (DFS), which pays for reducing consumption during peak grid stress events, and the Dynamic Containment service, which pays for fast-response frequency regulation.
Participation in these markets requires a compatible battery system, a registered aggregator, and metering capable of 30-second or shorter settlement. The revenue is event-based rather than continuous -- it is not a substitute for an export tariff but can supplement it meaningfully on sites with managed storage.
For a 50--100 kW commercial installation with managed storage in a typical UK location, annual export income at current SEG rates is approximately £2,000--£8,000 per year, depending on generation volume, self-consumption rate, and the export tariff selected. This figure is subordinate to self-consumption savings (which are priced at the avoided import rate) in most financial models -- but it is not negligible.
The financial model for a commercial installation should treat export income as a secondary benefit, sized conservatively against current tariff rates, with self-consumption savings as the primary value driver.
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