One million people are due to see their energy bills go up from today.
Electric Ireland is increasing its gas and electricity prices by 4%, adding an average of at least €30 to people's bills.
While PrePayPower prices are going up by just under 4%, meaning people will pay up to €50 more for electricity.
Daragh Cassidy from price comparison website Bonkers.ie outlined the likely impact on bills for consumers.
"For an average bill you're looking at an increase of around €30 - €40 in gas and electricity," he said.
"It mightn't seem like a huge amount but it's coming on the back of quite significant increases last summer as well from both of those suppliers.
"Both of these suppliers did freeze prices over the winter months to try and offset some of the higher costs for consumers."
Mr Cassidy said customers have three main ways to save on their energy costs.
"Switching supplier: it's quick, it's easy and it can all be done online in the space of a few moments.
"Customers can look at ways to reduce their energy consumption: perhaps installing LED lightbulbs which use up to 90% less electricity.
"And also look at ways of making the home more energy efficiant: attic insulation, wall insulation, things like that.