In this house, an EV helps power appliances — and the grid

At first glance, Frances Bell’s home in Oakland, California, doesn’t look like a postcard from the EV-powered future. But if a new program takes off, it could be a harbinger of what’s possible for homes across the state and the country.

Sure, there’s a shiny new Kia EV9 in the driveway and a black charging cord that runs from the car to an EV charger on the side of her house. But that’s a pretty standard setup in California, the nation’s leader in electrical vehicle adoption.

What makes this EV and the charger special is that they don’t just draw power — they also send it back to both Bell’s home and the grid.

As the CEO of Bidirectional Energy, Bell is outfitting homes across California with the same Wallbox Quasar 2 bidirectional direct-current charger that’s mounted to her house. This year, Bidirectional Energy and Wallbox are installing the equipment at about 120 homes as part of a state-funded pilot program that offers participants rebates for two-way chargers. Bell’s household was among the earlist to enroll, primarily to test the technology firsthand.

Their goal: to establish rules of the road for city and county permitting inspectors and utility interconnection engineers to handle these installations, similar to the standards for regular one-way EV chargers and backup batteries.

“From my perspective, a DC bidirectional charger is essentially the same technology as a solar or battery inverter,” Bell said. And those technologies are straightforward for a household to install.

Bidirectional systems are not anywhere near as simple to adopt. Pilot projects have been going on for decades, and federal and state governments have been working with automakers, charging manufacturers, and utilities to standardize the underlying technologies. Nevertheless, no large-scale programs exist today to allow customers to send power from their EVs to the grid or their homes.

If companies like Bidirectional Energy and Wallbox can crack the code on broader adoption, it could unlock serious benefits to the grid and consumers. Vehicle-to-grid (V2G) applications can turn cars into cheap energy storage for the electricity system and vehicle-to-home applications (V2H) can turn their cars into batteries that can power their house, saving them money.

Bell is convinced that the larger scale of this California program will help push the technology out of pilot purgatory and into the mainstream. 

“Previous bidirectional demonstrations were in the ones and twos,” Bell said. ​“When you get to 100 or more, you start to get to more standard processes. That’s how you start to scale.” 

Bidirectional charging on display

On a sunny May afternoon, Bell showed off her bidirectional charging system — and the benefits it provides.

The combination of Wallbox’s hardware and Bidirectional Energy’s software can actively draw power from the battery of a Kia EV9 to reduce a household’s costly utility bills, or to send power back to the grid during an outage or to prevent rolling blackouts. The system isn’t available for use with other EVs yet, though the companies are in discussions with undisclosed automakers.

“If the grid goes down, this will just kick in. You don’t have to walk out here and switch it,” Bell said. Then she flipped a switch in the Wallbox power recovery unit, which connects the Quasar 2 to Bell’s electrical meter and the grid beyond, to mimic a power outage.

With a click, Bell’s home was being powered by the Kia EV9’s battery, which stores about 99 kilowatt-hours of energy. That’s as much as seven Tesla Powerwall batteries, and enough to keep a typical home powered for about three days, Bell said.

Next, Jessica Kwong, Bidirectional Energy’s senior software engineer, sent instructions from her laptop to the company’s software platform to curb grid power use to avoid high time-of-use rates. Bell opened the Bidirectional Energy app on her iPhone to track the shift in home power coming from the EV battery. Then she toggled to a screen that showed the money she’s saving on her utility bill.

“Every day, when I plug in my car, this number ticks up,” Bell said.

Finally, Kwong mimicked a demand-response event, when utility customers are asked to either send stored energy back to the grid or simply use less energy when the grid is under stress. The EV’s battery started delivering 12.5 kilowatts of steady power back to the grid — and earning money for the grid relief it was providing.

None of this is particularly groundbreaking from a technical perspective, said Bell, who’s worked at battery companies including Tesla and Fluence and as a grid planner for Northern California utility Pacific Gas & Electric. And after years of work from automakers, charger manufacturers, and software companies, a lot of progress has been made on setting the technology standards for bidirectional charging, she said.

That’s why this Bidirectional Energy and Wallbox project, funded by the California Energy Commission, is focused on more than simply proving the technology works, she said. 

“We’re training some of the first installers, we’re getting the first interconnection processes established, and hoping to take that to other geographies.” 

Why vehicle-to-grid has remained elusive 

Bidirectional charging is an intuitive idea: Most cars spend most of their lives parked, which means that EVs are often sitting there with unused battery capacity that could be helping the grid, making money, or providing emergency backup services.

Lots of utilities are working on managed-charging programs, which ask customers to shift when their EVs pull power from the grid, whether to mitigate their contribution to peak power demand or to avoid overloading local circuits and transformers. That’s important, but it ignores EV batteries that could actively bolster the grid, not just reduce strain on it.

In California, the value of that latent EV capacity could be ​“an order of magnitude larger” than simply throttling EV charging, according to a 2021 study by University of California, Irvine, professor Brian Tarroja and Rochester Institute of Technology professor Eric Hittinger. It could also provide EV owners with thousands of dollars per year in utility bill savings and demand-response revenue, the report found.

Still, the approach has remained elusive — something of a holy grail for the EV industry.

Automakers have promoted these kinds of uses for years, from the earliest Nissan Leaf EVs to the now-discontinued Ford F-150 Lightning. Some automakers have designed their own vehicle-to-home connectors, as with the PowerShift charger from General Motors’ GM Energy business and Tesla’s Backup Switch for enabling Cybertruck Powershare mode. A growing number of EV-charger manufacturers make bidirectional-capable chargers that have been certified for use in California and in other states.

Many other states are pushing utilities to explore the concept, too, whether it’s using electric school buses as grid batteries or enabling homes to rely on plugged-in EVs for grid relief.

But California has set a goal of having 8 million light-duty EVs on its roads by 2030, making it ground zero for development via utility trials, state-funded pilot programs, and regulatory guidelines for streamlining bidirectional charger interconnections.

Wallbox, a Spanish company that does a lot of business in Europe, has seen a big uptick in North American sales in recent years, ​“especially when we talk about V2G,” said Oliver Waterhouse, the company’s director of strategic partnerships.

But injecting power from EV batteries to the grid ​“requires collaboration with utilities and grid operators,” he said — and while customers are eager to set up their EVs as backup batteries, ​“a lot of demand falls off when it takes 6 to 9 months to get an interconnection complete.”

Wallbox initially launched the Quasar 2 in partnership with Kia as a home backup system, he said. ​“Then Bidirectional Energy came in and said, ​‘Let’s make it V2G as well.’”

One of the trickier tasks for the two companies has been getting the components of the bidirectional system to feel like a single streamlined experience for the customer, Bell said. To achieve this, the companies have been establishing the linkages between onboard EV-battery management systems, the controls embedded in the chargers, and the inverters within those chargers, which deliver power to the home and the grid, Bell said.

Industry groups and certification organizations have settled on a plethora of technology standards for handling those tasks. But every automaker and charger manufacturer may implement them slightly differently, which means each combination has to go through its own round of testing.

Automakers also need to make sure cars are charged when drivers need them to be. ​“First and foremost, you want your car to be a car,” Bell said. Bidirectional Energy’s software allows customers to set what time in the morning they want to be fully charged and establish limits on how much power can be pulled from their EV batteries, she said.

Getting utilities to trust that these underlying controls can safely send power back to the grid has been the next challenge, Waterhouse said. Wallbox has gone through these processes with all three of California’s major utilities, he said, ​“but when you submit interconnection applications, they all have different questions.”

This is where doing hundreds of installations, as is the plan for the second phase of the Wallbox and Bidirectional Energy pilot, can start to smooth things out, Bell said. Utilities have sent engineers to pore over every detail of the first installations done by Wallbox and Bidirectional Energy, she said. That’s pretty similar to how utilities used to treat conventional home batteries, she noted.

“For solar and batteries today, there’s no engineer that gets sent to the house,” Bell said. ​“Getting these first 120 right will be really key for the next hundred or thousand — or million.”