Scientists say such energy-saving efforts could contribute to an even bigger environmental problem by adding pressure on North American's dwindling water resources.
In turn, this could lead to renewed U.S. demand for Canadian water, one expert warned here at the annual meeting of the American Association for the Advancement of Science.
This new dark side of going green emerged at a symposium that portrayed energy and water as conjoined twins.
University of Texas professor Michael Webber, an environmental policy specialist, said so-called green fuels for vehicles all require much more water to produce than ordinary gasoline.
Conventional oil refineries use comparatively modest amounts of water, largely for cooling.
Webber said the water required for an alternate fuel vehicle to travel a certain distance can be up to 100 times that required for a gas-powered vehicle.
This extra water use stems from the irrigation of crops like corn that are turned into ethanol, or in the production of the electricity for recharging hybrids.
Webber ranked the water requirements for existing hybrid electric and ethanol-fuelled vehicles, as well as hydrogen-powered vehicles of the future, and said they range from 10 to 130 times worse than today's gasoline-powered vehicles.
"I don't know of anybody who shops for fuels based on their water intensity," he said. "But as river levels continue to drop and aquifers dry up, this link between water and energy is going to become an issue at a higher government level."
Webber also pointed out that the water requirements of alternate fuels would be reduced if the electricity involved came from wind or solar power.
Further water savings could be had if ethanol was produced using non-irrigated materials such as lumber mill waste.
And he had a warning for Canada.
"Right now Canadians don't care about this because you're the most water-rich nation in the world.
"But you might care if the U.S. starts coming after your water because we're in trouble from the energy-water connection," he said.
Another researcher, Peter Gleick, said the energy-water link pervades modern society.
"We use a lot of water to produce energy and we use a lot of energy to move and treat water," said Gleick, who directs an institute in Oakland, Calif., that studies development, environment and security.
Yet government policies seldom treat energy and water in an integrated way, leading to serious problems, he said, citing nuclear power plants losing power capacity after rising river temperatures affected water used as a coolant.