Energy retailers could be forced to notify customers when they’re on expensive deals and tell them to consider cheaper alternatives.

The federal government last year directed retailers to write to customers to explain they could save hundreds of dollars by switching from so-called standing offers.

Now Energy Minister Josh Frydenberg has asked the Australian Energy Market Commission to make it a rule forcing retailers to contact customers.

He said the commission found the average difference between standing offers and the best market offer for electricity is up to $507.

In South Australia where one-in-10 customers are on standing offers they’re paying up to $800-a-year more on their bills.

Mr Frydenberg said the rule would require retailers to notify customers when discounts are about to finish or change and give them advance notice of price changes.

The proposed rule change would also allow customers to read their own energy meters and reduce new meter installation times.