Bord Gáis is increasing electricity bills by 34% and gas bills by 39%, from October 2.
The company is blaming significant increases in wholesale energy costs.
It says the average electricity bill will go up by over €48 a month, while gas bills will rise by over €43 a month.
Yesterday, Electric Ireland announced increases for one million customers, while in the past week SSE Airtricity and PrePay Power also announced hikes.
Bord Gáis' latest increase comes in from October 2nd, while the other companies will hike up price on October 1st.
Dave Kirwan, Managing Director of Bord Gáis Energy said:
“There is no precedent for the current energy crisis and consumers and businesses across the globe are grappling with very challenging increases in the cost of living.
"We deeply regret having to raise our prices but the scale of increases in wholesale energy costs leaves us with no choice.
"We continue to do everything we can to reduce the impact on our customers and keep our rates as competitive as possible.
"We are also pledging 10% of our operating profits to our Energy Support Fund to help customers of ours who simply can’t afford to pay for energy this winter.”
