If you've ever sat through an ESG audit and been asked 'but is this actually driving new renewable generation?', you've already met the difference between a REGO and a PPA.
REGOs: simple, certified, abundant
Renewable Energy Guarantees of Origin are tradeable certificates issued by Ofgem. They're abundant, cheap, and accepted by every major reporting framework. They're also detachable from the underlying generation, which is why critics argue they don't drive additionality.
PPAs: contractual, additional, complex
A Power Purchase Agreement is a multi-year contract directly with a renewable generator. Your business commits to buying a portion of that generator's output at a fixed price, typically over 5-15 years.
Because PPAs underwrite new renewable projects, they demonstrably drive additionality, your purchase caused new renewable capacity to be built.
When to choose which
REGO if: you're an SME or mid-market business with sub-£500k annual energy spend and need a defensible green tariff.
PPA if: you have public ESG commitments, are subject to scrutiny on additionality (CDP A-list, SBTi), and have annual electricity consumption above 5 GWh.
Both if: you want the cost predictability of a PPA for part of your load and REGO matching for the rest.
Marcus Brown
Sustainability Lead
Part of the Scottish Prime Energy procurement team, 500,000+ UK businesses switched, £150M+ saved.