Bright Energy is set to increase its standard residential energy prices by just short of 26% from 18 September.
This means that customers can expect to pay an additional €5.08 per week for their electricity, with an average annual bill of €1,295.
The green energy company said it has been forced to increase prices due to rising wholesale energy costs.
"A combination of low wind on the grid system and a number of power generators not being available due to essential maintenance means that electricity was not being produced in the volumes in which it was needed," explained Ciaran Devine, CEO of Bright.
"The knock-on effect is that providers, including Bright, have had to bear the higher costs associated with generating and maintaining the country's electricity networks."
When bright launched its 100% green electricity offering in Ireland in July 2020, it said an average megawatt of electricity cost €30.
Today, it said a single megawatt on the wholesale market can cost as much as €140.