When it comes to energy policy, electric cars may be best known for the impacts they don't have. They don't require foreign oil, and they don't spew greenhouse gases.

That's one reason green-conscious Palo Alto officials are abuzz over electric automaker Tesla's plans for a new powertrain plant in the Stanford Research Park. The move has the city poised to be a hub for an environmentally friendly industry that some believe will take off in the next decade.

But it also raises an issue that most other cities have yet to consider: What will happen if a significant proportion of the local population begins charging cars in their garage or at work every day?

It's a question that's especially relevant in Palo Alto, experts say, not only because of the affluent and environmentally minded population, but because the city runs its own electric utility.

In a new report, the city's utilities department takes an early stab at estimating the effects on the municipal power grid of a spike in electric car usage. It estimates that even 10,000 commuter cars charging during the day wouldn't tax the system as a whole. But depending on how those vehicles are clustered, certain local distribution transformers could have problems keeping up.

It's only a preliminary report, but the conclusion is clear: The city needs to start planning now to accommodate a potential electric vehicle boom.

"If everybody flushed their toilet at the same time, think about what happens to the water distribution system," said Patrick Valath, electric engineering manager for Palo Alto Utilities. "If thousands of these electric vehicles are charging at the same time, depending on the type of the charge unit and its draw on the system, it could have an impact."

In some areas, the report suggests, larger transformers and overhead wires could be needed. The research parks and the Stanford Shopping Center area, for instance, aren't equipped to deal with a heavy concentration of electric vehicle charging stations.

As for residential neighborhoods, they could generally deal with 10 percent of Palo Altans buying electric cars in the next 10 years, according to the report. But Valath said there could be localized problems if several homeowners on the same block come home and plug in their vehicles at the same time. Areas with newer, underground utility lines could probably handle the strain, but those with the older overhead wires might struggle.

Asher Waldfogel, a member of the city's utilities advisory commission, said he pushed for the report because he believes such an influx of electric cars is plausible in the city.

"If you look at penetration on green vehicle technologies, stuff like Priuses, we have way above average penetration on that in Palo Alto compared to other areas," he said. "There's a lot of interest around sustainability, and frankly, there's just the economic issue that people around here can afford to experiment with some of these new vehicle technologies."

Waldfogel said he wants the city to start thinking now about measures such as incentives for people to charge at night.

He's on the right track, said Mark Duvall, director of electric transportation for the Palo Alto-based nonprofit Electric Power Research Institute.

"In terms of energy requirements, plug-in vehicles and plug-in hybrids are relatively modest," Duvall said. "Drop 10 million on the ground tomorrow and they would use less than 1 percent" of the nation's electricity.

But that doesn't mean there won't be impacts, he added. It's just that they'll be felt first in local distribution systems — not the power system as a whole. And Palo Alto is a likely candidate.

Incentives have to be part of the solution, Duvall said. If electric vehicle owners all charge their cars late at night, the impact on the grid — even locally — will be minimal. In fact, he said, electric cars could be the "hot app" for smart meter systems that allow customers to monitor their electricity usage in real time and turn things on and off remotely. Unlike air conditioning systems that businesses have to turn on during the peak daytime hours, cars can be charged just as easily while their owners are asleep.

"I think a lot of cities are starting to think about this," Duvall said. "It's something I think in a year or two years from now, almost every major city or utility will be thinking about in some way or another."

The Palo Alto Utilities Advisory Commission will discuss the report in a 7 p.m. meeting Wednesday at City Hall, 250 Hamilton Ave.

E-mail Will Oremus at woremus@dailynewsgroup.com.