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A push is on to speed up electric-vehicle powering. What happens will shape life on the road in coming years.

A race is on to speed up electric-vehicle charging.

The U.S. government is trying to spur the buildout of so-called fast chargers that can charge EVs in about 15 to 40 minutes. That’s still slower than a traditional fill-up at a gas station, but faster than the hours-long experience at public chargers that deliver power at 7 to 19 kilowatts.

On the highest end of charging, trucking companies and charger manufacturers have installed and piloted systems with a megawatt power level. Some prototypes extend to 3 megawatts and higher. The National Renewable Energy Lab and other national labs are developing megawatt-level designs to charge trucks in less than 30 minutes.

Automakers are also looking at ways to improve the batteries themselves to speed charging times.

But there’s much debate about just how fast charging will need to be and where the chargers should be located. How this debate plays out could shape life on the roads in coming years.

Some in the EV industry think super-fast charging will need to happen in order for consumers to widely adopt the vehicles. They say making fast charging easily available is a key to relieving “range anxiety”— drivers’ fear that they will get stuck on the side of the road without power.

Others argue that this view is a throwback to the fueling habits of the combustion-engine era. Faster chargers may be needed on highways between cities so people can travel longer distances. But some in the industry say that beyond creating a backbone of highway chargers, it would be better to focus on installing massive numbers of slower chargers at places where people park–offices, restaurants, shops, apartments–in order to make charging a car a convenient and ubiquitous experience.

Most charging now happens at home, and that’s likely to continue. Typical earlier EV adopters have been higher-income owners of single-family homes with a garage or driveway where cars can sip electricity at a slow rate for hours. But those in multifamily housing have less access to charging.

In an effort to speed the switch to EVs, the U.S. government in 2021’s infrastructure law approved spending $7.5 billion over several years to increase the availability of chargers. So far around 7,300 U.S. locations have fast chargers, and much of the equipment is early-generation.

Fast-charging stations for electric vehicles, like this one from EVgo in Vienna, Va., are rolling out across the U.S. Photo: SAUL LOEB/AFP/Getty Images

Power levels at existing fast chargers range from 50 kilowatts to 350 kilowatts. They are able to charge a battery to 80% in 15 minutes at the higher power level to around an hour at the lower end, depending on the EV battery’s charging rate. So far only a handful of higher-end passenger EVs on the market have the capacity to be able to take advantage of a 350 kilowatt charger.

The more common kind of public charger, known as a level 2, has a power output of around 7 to 19 kilowatts and uses a similar outlet as that for an electric clothes dryer. It’s often available at apartments or offices and takes a battery up to 80% charged in four to 10 hours.

A standard wall outlet adds a few miles worth of charge per hour and could take 40 hours or more to fully charge a car, but generally adds enough range overnight that EV commuters often rely on it. Many, though, add a level 2 charger to their garage.

Megawatt chargers, being tested for the trucking industry, are considered the realm of heavy commercial vehicles with massive batteries, such as 18-wheelers.

There are tradeoffs in cost and practicality. Fast chargers require costly utility infrastructure and charging equipment; ultra-rapid charging would be even more expensive.

“Higher power costs more,” Bowermaster says. “You get to a point where for these higher power levels you’d need bigger and bigger wire. At some point the wire gets so big that not only it’s heavy, but it can’t readily bend to curve around the charging port.”

That could create accessibility problems for disabled and older drivers. But that might be solvable with mechanical assists to lessen the weight of cables and connectors or by using robotic arms to automate the process, says Jonathan Levy, chief commercial officer of EVgo, a fast-charging provider. Robots would also be able to charge autonomous vehicles.

Another solution for speeding up charging could be a solid-state battery in which the electrolyte that conducts the electric current is a solid, rather than a liquid as used in most batteries today. Solid-state batteries could be a breakthrough to get to higher energy density and faster charging speeds.

“You can go further on a full charge and [the battery] takes the charge faster,” Levy says. “There’s been some chatter about that being three to five years away for a while.”

Nick Nigro, founder of the research group Atlas Public Policy, expects the passenger-car market to move toward a standard of 350-kilowatt charging. “It’s not clear that there’s going to be much value in going much higher than that for regular passenger vehicles,” he says.

An added factor is that 350 kilowatt charging isn’t consistent, even if it’s available. Outdoor temperature extremes and the state of a vehicle’s battery have an effect on charging. The rate slows significantly once a battery reaches about 80%—known as the charging curve.

“If you plug into a 350-kilowatt charger, if your battery is empty it will charge that fast. As it gets more full it’s sort of harder to push [the energy] in,” says Jenny Baker, senior lecturer in mechanical engineering at Swansea University in Wales, who researches solid-state batteries and environmental impacts.

“Eventually you might as well be just trickle charging,” she said, referring to being plugged into a standard wall outlet.

Each car battery has a different charging curve that impacts how long it can sustain higher rates of charge. Automakers are trying to extend the charge curve so EVs can consume more of the kilowatt power delivery for a longer duration, says Ken Tennyson, senior director of quality and conformance at EV fast-charging provider Electrify America. “By doing that you can actually bring down the duration of the charge session.”

Other changes would optimize the power delivery to the battery. Most EVs use a 400-volt system, but some automakers are moving to 800 volts, doubling the power that the same current would provide, Tennyson says. But an important caveat: Getting drivers the fastest possible charge would require not just an 800-volt EV but also the highest-level charging equipment.

Write to Jennifer Hiller at jennifer.hiller@wsj.com