Bord Gais Energy customers will be noticing a massive increase in their gas and electricity bills from April 15 after the company announced an end to its winter price pledge.
However, even if customers cut back on their usage as much as possible, they will still see a substantial rise in costs.
Bord Gáis confirmed to the Irish Independent that the hikes would also apply to standing charges as well as the cost per unit of gas and electricity.
This means even customers who reduce their usage to zero will pay more.
The huge increases will see customers pay an extra €700 a year for gas and electricity with fears still other providers will now follow and up prices.
Although standing charges are not affected by rising fuel prices, the company said it reflects rising business costs.
Bord Gais announced on Tuesday that electricity bills would increase by 27 per cent while the average gas bill would go up by a massive 39 per cent.
In a statement, the provider said: "With high global wholesale energy costs and market volatility expected to continue for some time , Bord Gais Energy has today confirmed that its winter price pledge, which protected customers over the colder winter period, is ending.
"Regrettably, the company is increasing the average electricity bill by 27% and the average gas bill by 39% . The changes will take effect from 15 April 2022."
Adding: "Working in partnership with the Money Advice and Budgeting Service (MABS) and other charities, Bord Gais Energy is establishing an energy support fund and will provide tailored advice to help customers."
The increase will add around €350 a year to the average household's gas bills and €340 to the average annual electricity bills.
Minister for the Environment, Climate and Communications Eamon Ryan warned on Tuesday that the Government would not be able to combat every increase Irish consumers are facing.
Speaking in Washington DC, with Taoiseach Micheál Martin for the annual St Patrick's Day trip, Minister Ryan said: "The most important measure is to try and start reducing our usage. Switching into the spring will help, use of gas will naturally fall in the heating sector."
While Taoiseach Micheál Martin acknowledged that the price hikes would hit the poorest hardest.