POWER prices are set to rocket after three major retailers announced increases of up to 20 per cent and $600 a year for the average customer in some states.

Origin, EnergyAustralia and AGL have all announced price increases for electricity and gas starting from July 1.

Small businesses may be the hardest hit, especially Origin customers in South Australia, which will see prices rise by a whopping $1453 a year when increases to gas and electricity bills are combined.