Household electric bills for customers of Power NI are set to fall by 10.3% from April.
The company has said the average annual saving will be about £50.
The move has been made possible by a steady fall in the price of wholesale gas, the main fuel used in electricity generation.
According to Power NI, its business and farm customers will also see reductions of between 7% - 11%.
Power NI is Northern Ireland's largest electricity supplier, used by more than 500,000 homes.
Its managing director, Stephen McCully, said: "This is the third year in a row we have been able to cut or freeze prices.
"This means more money in the pockets of householders and with farms and businesses also seeing a similar reduction it is good news all round."
Power NI is facing ever greater competition from rival suppliers.
Richard Williams, head of energy at the Consumer Council said: "We would now like to see the other domestic electricity suppliers follow suit."
Earlier this month, Open Electric announced a 9% cut, while in January, SSE Airtricity announced a 1% reduction.