A third major energy retailer, Origin Energy, has announced double-digit electricity price increases in South Australia and New South Wales from next month.

Origin joins other major retailers AGL and EnergyAustralia, which have both outlined significant price hikes in the past week.

Origin's electricity tariff for residential customers in South Australia will rise by 16.1 per cent from July 1, while the tariff for small businesses will increase by 18 per cent.

A combined annual gas and power bill for an average residential customer in that state will rise by $425.

The combined bill for an average small business will rise by more than $1,500.

Electricity tariffs for both business and residential customers in New South Wales will soar by more than 15 per cent.

The price rises are more constrained in Queensland, where residential customers will pay an additional 3.5 per cent on their bill.

Retail prices for Victoria will be set in December.

Origin Energy price increases 2017/18

Market Electricity (average residential) Gas (average residential) Electricity (average small business) Gas (average small business) South Australia $344 $81 $1,012 $586 New South Wales $310 $77 $823 $343 Queensland $67 $18 $307 $117

Origin Energy said the changes reflect the fact that Australia's energy market is in transition, with changes to supply and demand impacting on the wholesale price for energy.

"We are protecting our most vulnerable customers from rising power prices by ensuring those in our hardship program will not pay this price increase," said executive general manager of retail Jon Briskin.