Energy prices have jumped by 17% in the year to November.
Bord Gais said increases in both oil and gas drove its energy index up by 4% last month.
However, energy trading analyst with Bord Gais Michael Kelleher said markets were indicating lower energy prices early next year.
"We have seen relatively mild weather so far this wineter. Therefore, there may be enough stocks around for the remainder of the winter and into the spring to warrant slightly lower prices," he said.