Electricity bills for SSE Airtricity customers are set to increase from November 1.
The company has announced a 5.6% hike in prices.
It says the change is due to increases in networks charges and rising wholesale energy costs.
They said the increase will not be applied to customers using Pay-As-You-Go meters.
David Manning, Director of Home Energy at SSE Airtricity, said: "Today’s decision is not taken lightly and is driven by rising costs outside of our control.
"These include recently announced increases to regulated charges for using the electricity networks, which affect all suppliers, as well as prolonged increases in the cost of wholesale energy on global markets."