Households could see their energy bills rise by up to £183 at the end of the summer holidays.
That’s because nine tariffs are due to expire by the end of the month, eight of which will increase customers’ bills.
That means an increase from £897.47 to £1,080.57 per year for those who are on a Scottish Power online fixed price energy August 2016 and change to the standard offer. Other families or businesses could see average price rises of £135.17 a year but most customers could save up to £300 by switching supplier.
Ben Wilson, Energy spokesperson at Gocompare.com, who released the findings said: “With autumn approaching households should be looking ahead to ensure they’re not stung by a price rise as their usage begins to creep up.”