The Bord Gáis energy index was unchanged last month but rose by 27 per cent compared to August 2010.

The index stood at 139 last month as a fall in oil and natural gas prices was offset by increases in both coal and electricity prices.

The oil element of the Bord Gáis Energy index is down 2 per cent to 146 after oil prices fell sharply early on in August due to fears of a double dip recession in the US and Europe.

The natural gas element of the index was down 4 per cent to 173 while the coal element was up 1 per cent to 150.

The electricity element of the index was up 5 per cent to 119, driven by an outage on the Moyle interconnector to the UK and other generator outages which created a need for more expensive generation plants to be scheduled on at peak demand times.

The Bord Gáis energy index has risen sharply over the past few years and is now 57 per cent higher than in August 2009.

"August continued the trend of mixed economic signals from the developed economies while growth remained robust in China and other Asian economies. There were also significant developments in the conflict in Libya which led to hopes for the resumption of the country's oil production. These economic and geopolitical issues resulted in increased volatility in oil prices," said Michael Kelleher, energy trading analyst at Bord Gáis Energy.

He added that future markets continue to point to an increase in the energy index in the fourth quarter of this year.

"Higher natural gas futures prices are the main driver of a higher outlook for the Energy Index. Concerns over increased demand for the fuel from Japan and Germany due to nuclear power generation shutdowns and the high oil prices seen to date in 2011 which are used to set the price for natural gas for the coming winter are combining to give a bullish outlook for gas prices."