Electricity bills are set to rise by over 35%, and gas bills to by 39% from October 1, SSE Airtricity has announced.
It is believed to be among the largest price hikes seen in the energy sector in the country.
In a statement the company said the war in Ukraine and "heightened geopolitical tensions" have resulted in what it described as "sustained and unprecedented increases in wholesale energy costs".
The unit price is being increased by SSE Airtricity for it electricity by 45.2% and the unit price of its gas by 46.3% from 1 October.
The move is expected to impact around 250,000 electricity customers and 85,000 gas customers.
The increase will add almost €600 a year to the average customer’s electricity bill and over €500 a year to their gas bill, according to bonkers.ie.
Independent.ie personal finance editor Charlie Weston told RTÉ News that there have been over 50 prices increases in the country by energy suppliers since 2021.
Over the course of a year, the latest increase will add almost €600 to the average customer's electricity bill and over €500 a year to their gas bill.
The company has pledged a customer support fund of up to €25m to assist around 60,000 eligible customers.
It says it will contact eligible customers directly through September with the details of the support.
Managing Director Klair Neenan said they are "acutely aware" of the impact the move will have on households.
"We know this news will be disappointing for our customers. It was hoped market volatility would ease, but the global energy crisis continues to impact gas and electricity costs for all energy suppliers.
"However, we are acutely aware of the impact this has for households and are working hard to help where we can," she added.
The company has said that any customers who having difficulty in paying their energy bills to contact them in order to find a solution, such as flexible payment plans.
The latest increases comes just after new measures are to be introduced to protect electricity and gas customers this winter in the wake of increasing prices, the utilities regulator has announced.
Included amongst the measures is an extension of the period during which customers cannot be disconnected. There will also be an easing of debt repayment policies.
According to the Commission for Regulation of Utilities (CRU). these efforts are being taken “in the context of the current volatility in global energy prices”.
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