Every kWh of solar a site consumes itself displaces grid electricity at the full retail rate (~28-32p/kWh for commercial supplies in 2026). Every kWh that's exported to the grid earns only the export tariff, currently ~4-5p/kWh under SEG (Smart Export Guarantee), or possibly more under a wholesale-linked contract.
That's a 5-7× value gap per kWh between self-consumed and exported electricity. For PPA economics, the on-site self-consumption percentage is therefore the single largest driver of project value.
Sectors with high self-consumption have strong solar economics:
- Manufacturing (often 75-85% self-consumption due to constant baseload) - Cold storage / food processing (75-85%) - Data centres (95%+, far more demand than solar can meet) - Hospitals (75%, 24/7 baseload) - 24/7 logistics depots (60%)
Sectors with lower self-consumption need different thinking:
- Schools (50-55%, weekday-heavy, summer holidays a problem) - Offices (60%, daytime aligned but lower density) - Retail (70%) - Warehouses (45%, ironically, often huge roofs but limited demand)
The interventions that improve self-consumption: matching system size to load (don't over-spec), battery storage to time-shift solar into evening peaks, EV charging on-site (consumes solar during the day), and switching baseload processes to daytime where possible.
For a low-self-consumption site, ground-mount solar can be made to work via a sleeve PPA structure where the export goes to a corporate buyer elsewhere, but this requires a sophisticated developer and a willing corporate offtaker.