As many as 50 hybrid nameplates could be on the market in five years, according to a recent study by the Automotive Technology Research Group in California.

The hybrids would account for annual North American sales of 800,000 to 1 million units, a huge increase on 2004 when only 85,000 hybrids were purchased, reports Autoweek.

A panel of powertrain experts made the predictions last week at the Automotive News World Congress, saying that consumers will pay a premium for hybrids in the near future.

The panelists predicted that over the next 25 years internal combustion engines will become part of a mix of powertrain options that include diesels, hybrids, fuel cell vehicles and internal combustion engines that burn hydrogen.

It was pointed out that the recent development of Delphi's fuel cell to power a vehicle's electric system means that fuel cells may be viable before hydrogen fuelling stations become readily available, signifying further opportunities for the industry.

Hybrids are also being considered as a way to revive the automotive industry, with the suggestion made that Detroit's struggling automakers should turn to hybrids to increase sales.

The success of recent hybrids has encouraged automakers to step up their efforts. Toyota announced plans this month to produce 100,000 Prius cars for the US, double the 2004 figure. Ford and Nissan are also accelerating production.