Automakers are rethinking fuel-saving technologies for passenger cars as hopes dampen that electric vehicles will play a big role in cutting CO2 emissions.

At the Geneva auto show there was a growing awareness that conventional hybrids and slow-selling battery cars simply won’t be enough to meet rigid EU emissions limits.

Among those showing off new ideas in Geneva was Volkswagen, which presented its diesel-electric XL1 – a low-slung two-seater that burns less than a liter of fuel per 100 kilometers. PSA/Peugeot Citroen unveiled a compressed-air hybrid.

Automakers are broadly on track to meet the EU’s interim goal of trimming vehicles’ average CO2 output to 130 grams per kilometer by 2015. But drastic steps are needed to meet the 95 gram target set for 2020 and the potential for tougher standards after that.

“We can’t get the necessary gains we need with traditional technology any more. We’re seeing a real break with the past,” PSA innovation chief Jean-Marc Finot said in an interview.

Earlier this week, General Motors CEO Dan Akerson said breakthroughs in battery technology are on the horizon and reiterated GM’s plans to have about 500,000 vehicles on the road by 2017 with some form of electrification, including the Chevrolet Volt.

Renault-Nissan has spent billions to develop electric cars including the Nissan Leaf and Renault Zoe that aim to win big neumbers of buyers in the mainstream compact and subcompact segments..

But KPMG said in a survey in January that optimism about the future of electric vehicles has “dampened considerably” throughout the auto industry.

Arthur Wheaton, automotive expert at Cornell University, said: “Battery technology has not been able to resolve the century-old problem of too much weight and limited range capability.”

World leader Toyota, which launched the Prius hybrid in 1997, dropped plans for broader sale of the battery-powered eQ last September, saying it had misread demand.

GM’s Opel scrapped plans for a fully electric Adam subcompact, citing high costs, while Audi shelved the electric R8 coupe and Nissan slashed the price of its Leaf after disappointing sales. “Demand for electric cars isn’t where we thought it would be,” said Francois Bancon, Nissan’s upstream development chief. “We’re in a very uncertain phase, and everyone’s a bit lost.”

For automakers battered by Europe’s prolonged market slump, the investment costs are a big concern. Several have joined forces to develop new technologies, most offering some degree of “hybridization” of combustion engine and electric power.

“By now we would have seen a standardization based on the pure electric car if it had turned out to be the solution,” said Guillaume Faury, Peugeot’s executive vice president for research and development. “That’s why we’re seeing so many micro-hybrids, mild hybrids, full hybrids, rechargeable hybrids, range extenders and battery cars.”