The scheme is intended to improve chances to make like-for-like comparisons across companies offering a diverse array of green products, from deals which contribute a percentage of customers’ bills to green charities to deals which offer homeowners incentives to install solar panels.

“Energy companies have a wide range of measures in place that qualify them to advertise their tariff as ‘green’, some of which have a more positive effect on the environment than others,” explained SimplySwitch.com’s Karen Darby.

“A system to objectify the ‘greenness’ of each tariff” would be a major advance, she added.

Current take-up of green tariffs across all energy providers remains low, at just nine per cent, Ms Darby noted.

The government should back energy companies’ green schemes with subsidies to bring down their cost for customers, she urged, possibly by waiving VAT on “the most eco-friendly tariffs” once Ofgem had determined which those were.

Meanwhile, Scottish and Southern Energy has taken steps to reward customers for using less energy in a move it has flagged as promoting green practice, uSwitch.com recorded.

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