The Bord Gáis energy index rose by 2% in September to give a reading of 111, with oil prices increasing by 10% last month.
The index looks at the price movements in the wholesale energy markets and is made up of the four key energy commodities of oil, gas, coal and electricity.
Bord Gáis says the index would have reached a two- year high if currency movements had not absorbed the increased prices in most of the commodities. It says the strengthening euro against the US dollar and sterling prevented the energy index from reaching 117 - a level not seen since October 2008.
The September index shows that the price of oil rose from $74 to $82 a barrel last month, while coal prices were flat until the final week of September when prices per tonne rose to $96.37 from $93.
Natural gas prices were very volatile during the month and electricity prices rose by €2 per megawatt to average €56. Bord Gáis says that due to the darker evenings, the increased electricity demand has resulted in more expensive electricity peaking plants being called in to produce the extra power needed.
'The advent of winter is already having an effect on the index with electricity prices increasing as a result of the darker nights,' commented Michael Kelleher, energy trading analyst at Bord Gáis Energy.
'Currency movements will continue to have a major effect on energy index movements - the inverse relationship between the US dollar and oil prices was again evident in the back end of September,' he added.
