Firmus gas prices to rise by almost 18% Average bill in the Ten Towns licence area will now be £518 per year, Regulator says Firmus is putting its prices up (Image: Getty) Never miss a thing from Belfast and beyond - sign up for FREE newsletter direct to your inboxInvalid EmailSomething went wrong, please try again later. Subscribe When you subscribe we will use the information you provide to send you these newsletters. Your information will be used in accordance with ourPrivacy Notice. Thank you for subscribingWe have more newslettersShow meSee ourprivacy notice Gas company Firmus is to hike its prices up by nearly 18%, they announced today.