The increase in gas distribution charges paid by all gas suppliers and a tariff adjustment to recover the company's long term supply costs are the two main reasons given by the regulator for the price hike.
Around 115,000 domestic and 6,500 small business customers will be affected.
Airtricity, who recently acquired Phoenix Gas, said the change was the equivalent to an increase of under £1 per week or 13p per day on a typical domestic gas bill. The cost of its electricity prices would not be impacted by the gas bill increase, the firm added.
Shane Lynch, the Utility Regulator, said that although this is the first gas price increase for two years, the impact it will have on consumers at a time when household and business budgets are stretched is recognised.
"We never approve proposals for tariff increases without extensive scrutiny. Our scrutiny during this tariff review has reduced the extent of the increase sought by Airtricity.
"If gas costs decrease, we will act as soon as possible to ensure that this reduction is reflected in consumer bills," he added.
Mr Lynch explained that a significant part of the increase was the Competition Commission's determination on the Phoenix Natural Gas Ltd price control.
"The Utility Regulator's determination on the Phoenix Natural Gas Ltd price control would have resulted in a smaller increase for natural gas consumers.
Mr Lynch added. "The tariff increase will still leave the standard domestic average tariff for Greater Belfast gas consumers lower than their equivalents in Great Britain or the Republic of Ireland.
"It is also important to note that consumers who choose natural gas enjoy a significant running cost savings over those who use oil to heat their homes," he concluded.
Sinn Féin Phil Flanagan MLA said the price hike will invariably have a very negative impact on fuel poor households and those living on fixed incomes.
"Such a considerable price rise shows the volatility of fossil fuels and further reinforces the need to move away from gas and oil to sustainable forms of energy, which will reduce consumer bills, increase security of supply and protect our environment by reducing harmful emissions, " the party's Energy spokesperson said.