Renewable energy group Airtricity has agreed to spend more than $300 million (€245.1 million) on turbines to meet rising demand for wind energy in the US.

The company will buy 250 turbines from Japan's Mitsubishi Power Systems, the largest ever order for the Mitsubishi Heavy Industries subsidiary.

Airtricity will receive the order over the course of next year and has the option to buy a further 200 one-megawatt turbines in 2008 from Mitsubishi.

"The next deal will be 200 to 250 turbines, so we'll be heading for the $600 million mark," an Airtricity spokeswoman said. "The price of turbines could change next year, so we don't know the exact value of the next order."

The turbines will be used to supply unspecified wind farms in Texas, New Mexico and Colorado as well as other wind farms owned by Renewable Generation Inc, an Austin-based wind energy company that Airtricity agreed to purchase last month for about $10 million.

RGI, as the Texan company is known, has more than 1,000 megawatts of wind farms at various stages of development.

Airtricity unveiled plans in June to invest at least $1.5 billion in the US market over five years, starting with a $270-million investment in wind farms in Texas, New York and Idaho.

The move is designed to enable Airtricity generate at least half its total revenue by 2010 from a series of projects in the US, where there is limited wind energy capacity.

"We have managed to secure this deal against intense competition for turbines during a time of world shortage," said Eddie O'Connor, the chief executive of Airtricity.

The Irish company, which is 51 per cent owned by National Toll Roads, supplies renewable electricity to more than 50,000 commercial customers in the Republic and Northern Ireland.