Around 136,000 gas Firmus gas customers will see their tariff increase from next month amid the ongoing impact of the crisis in the Middle East on energy prices.
Firmus Energy, which is the regulated supplier to 77,000 customers on the Ten Towns network, has confirmed an 8.98% increase for households and small businesses from October 1.
The energy firm said it will add around £84 per year to the average annual household bill.
Firmus said its Greater Belfast customers will face a 12.5% increase from October 8, adding around £144 to the average annual household bill.
It follows last week’s announcement by SSE Airtricity of a 19% price increase for just over 205,000 gas households from October 1, adding around £174 to the average annual bill.
Cargo ships are seen at sea near the Strait of Hormuz. (Fatima Shbair/AP Photo/Fatima Shbair)
The wholesale price of natural gas hit £1.80 per therm on Thursday, more than double the market price before the US launched its assault on Iran at the end of February.
The failure by the US and Iran to agree a long-term deal over the Strait of Hormuz has contributed to a steady rise in wholesale natural gas and oil prices over the past month.
Gas prices are now at the highest level since 2022. If they remain elevated, it will likely result in fresh hikes in electricity tariffs this winter.
Natural gas remains a key factor in electricity generation on the island.
Home heating oil prices have also surged this week, with the average order of 500 litres reaching £494 on Friday, almost £50 higher than seven days ago and £150 more expensive than the average on July 1.
Commenting on its new price increases, Sharleen Winning, head of regulation at Firmus Energy Supply, said: “We cannot ignore the impact the situation in the Middle East is having on the cost of energy, and unfortunately this has left us with no option other than to increase our tariffs.
“We have held off for as long as we could in the hope of a resolution that would lead to a reduction in the global wholesale prices.”
Dublin-based Yuno Energy, which acquired the Firmus supply business for £35m in November 2024, has been on an aggressive marketing drive to win new customers in Greater Belfast, where it competes with SSE Airtricity.
It added more than 10,000 new customers on the network in 2025, with the numbers continuing to rise this year.
“As Northern Ireland’s largest gas supplier by volume, we want to provide the best value possible to all our customers and we have demonstrated that when we are in a position to reduce tariffs, we do so without delay, and we hope to be able to do so again, once the global markets allow this,” added Ms Winning.
The Ten Town network runs from Derry city, along the north coast and down through Co Antrim into parts of Armagh and Co Down to Newry.
The Greater Belfast pipeline runs from Larne through Belfast and Lisburn to north and east Down.