Green energy certificates

Many energy suppliers in the UK offer “100% renewable” electricity tariffs. To understand these claims, you need to understand the role of REGO (Renewable Energy Guarantees of Origin) certificates and how green energy is tracked in the national grid.

What is a REGO?

Every time a renewable generator (like a wind farm) produce one megawatt-hour (MWh) of electricity, they are issued one REGO certificate by Ofgem. This certificate acts as a “proof of birth” for that clean energy.

How suppliers use them

When an energy supplier sells you a “100% renewable” tariff, they must prove to Ofgem that they have purchased enough REGO certificates to match the total amount of electricity their customers have used over the year.

The “Greenwashing” Debate

There are two main ways suppliers source their green energy:

  1. Direct Investment (Deep Green): Suppliers like Good Energy, Ecotricity, and sometimes Octopus own their own renewable generation (wind/solar farms) or have direct contracts with independent generators to buy their power AND their REGOs.
  2. Certificate Trading: Some suppliers buy “brown” electricity from the general wholesale market and then buy separate, cheap REGO certificates from other generators to “match” it.

Why it matters

The direct investment model provides much more support for building new renewable energy in the UK. The certificate trading model, while legally compliant, is often criticised as “greenwashing” because it doesn’t necessarily result in more clean energy being added to the grid.

Green Gas (RGGOs)

While electricity is increasingly easy to source from renewables, “Green Gas” is much rarer.

  • Biomethane: Gas produced from organic waste (anaerobic digestion).
  • RGGOs: Renewable Gas Guarantees of Origin are the gas equivalent of REGOs.
  • Carbon Offsetting: Many “green gas” tariffs actually use standard natural gas and then “offset” the carbon by investing in environmental projects elsewhere (like planting trees).

The Gold Standard: Look for suppliers that are rated as “Tier 1” by independent researchers or those who have ” derogation” from the Ofgem price cap, as this usually indicates they are providing genuine support for new renewable generation.

How to choose a truly green supplier

  1. Look for direct PPAs: Does the supplier have Power Purchase Agreements (PPAs) with specific wind or solar farms?
  2. Check their fuel mix: By law, every supplier must publish their “Fuel Mix Disclosure” annually.
  3. Support new generation: Choose suppliers that actively invest in building new renewable infrastructure.
  4. Avoid offsets where possible: Prioritise suppliers that use biomethane or direct renewable contracts over those that rely heavily on carbon offsetting.