According to the regulator, consumers choosing green tariffs must be able to see evidence of whether or not there is an environmental benefit from particular tariffs.

An increasing number of tariffs making environmental claims are not certified through the Green Energy Supply Certification Scheme, Ofgem said, leaving the consumer with no way of knowing what, if any, benefits there will be.

Ofgem is proposing three key principles for future green tariffs. They should be transparent, stating clearly what the environmental benefits will be and publishing an annual report, able to demonstrate that any benefits are derived through a customer’s tariff choice and not because of subsides or supplier obligations, and they must have evidence that verifies where the electricity supplied in a tariff comes from.

Sarah Harrison, senior partner for sustainable development at Ofgem, said: “We believe these changes will give consumers confidence to make more informed decisions about buying tariffs based on renewable energy.”