Scottish Power is set to launch a pre-pay energy tariff that allows customers to pay for ‘days’ of gas and electricity.

Customers can buy up to 180 ‘days’ of gas or electricity, calculated from their previous usage. They can track usage via an app and will see how many days they are remaining. The tariff – which is ‘coming soon’ – will initially be available only to existing customers, who can register their interest online.

SSE, meanwhile, has made a bid for new customers by offering its cheapest deal exclusively to Energy Helpline customers.

Energy Helpline said on its website that it had “the UK’s cheapest publicly available energy deal exclusively for a limited time.

“It comes from a Big Six company widely regarded as offering the best customer service in the UK. … We expect it will save you a lot of money.”

The deal excludes pre-pay customers.