What is bidirectional EV charging?
The installation of EV chargers is quickly becoming a must-have offering in a solar installer’s services. As more solar manufacturers begin making EV products, solar contractors usually have the right connections and knowledge to do another electrical hookup in a garage. Bidirectional EV charging should also provide new installation opportunities for contractors as customers seek additional revenue and backup-power options for their EV investments.
How a traditional, unidirectional EV charger works
Basically all EV chargers installed pre-2023 only allow power to flow in one direction — from the electricity source (home, business, charging station, etc.) to the electric vehicle. While all EV chargers move power in the same direction, there are different types, including Level 1 and 2 chargers and fast DC chargers. Level 1 and 2 chargers just move power — the electric vehicle itself takes the supplied AC power and converts it to DC power to charge the vehicle’s battery. A fast charger does that AC-to-DC conversion itself to deliver DC power directly to the vehicle.
How a bidirectional EV charger works
A bidirectional charger allows for both regular charging of an EV’s battery and exporting of an EV battery’s power into a home or onto the grid. This vehicle-to-grid (V2G) and vehicle-to-home (V2H) power transfer is also collectively known as vehicle-to-everything (V2X).
This is a big advancement in the EV and energy storage markets. An electric vehicle’s battery is an underused asset — it’s a portable energy storage system (ESS) with a much bigger capacity than the stationary ESS options sold today. The ability to use an EV battery’s power for more than just driving could transform how customers and utilities think about solar and storage adoption.
“A Nissan LEAF has 4.5 Powerwalls under the hood, and they come free with the leather seats and air conditioning. The Ford F-150 Lightning has more value under the hood in storage than the cost of the vehicle, literally,” said David Slutzky, CEO of V2X software developer Fermata Energy.
Bidirectional chargers are just starting to hit the market. As of early 2023, only two bidirectional chargers have achieved UL 9741 certification, the standard that covers bidirectional charging equipment and includes functionality to export power to the grid: Fermata Energy’s FE-15 charger and the Ford Charge Station Pro, made by Siemens. But plenty of other companies, including Wallbox and Enphase, are working on their own bidirectional chargers, so the market should have more options in 2024 and 2025.
Bidirectional chargers have been slow to develop because the technology is much more advanced than what’s in a unidirectional EV charger. A more powerful inverter has to be installed to allow for the AC-to-DC power exchange and back again. That dual power transfer generates heat, so more fans and higher-rated enclosures have to be used. Automatic transfer switches must be included if the vehicle wants to work with the grid. Add in software developments to ensure the consumer can use the charger like any other smart device and the utility can access that power, and suddenly you have a much bigger and more complicated product to manufacture.
But once more bidirectional chargers are UL-certified and on the market, solar contractors should have no problem learning to install the new product. If they know how to install an ESS or even just a solar inverter, they can install a bidirectional charger.
What still needs to be done
Interest has grown around bidirectional charging largely due to Ford’s announcement that the 131-kWh battery inside the F-150 Lightning could be used as emergency backup to homes. While still an advantageous second use for an EV battery, the real benefit of bidirectional charging and V2X is in interacting with the grid.
“Most people today are thinking about V2H as backup power and that’s because of the Ford Lightning. Once people understand that we can produce energy savings on our utility bills through grid parity, that’s going to change pretty quickly,” said Shawn McLaughlin, CEO of home energy management company Emporia Energy. “Early adopters will buy for backup, and then when they can reduce their energy bill by 50%, word of mouth will spread. Within the next three or four years, the majority of use will be managing energy efficiency and savings during grid parity vs. just using during grid outages.”
To enable this, utilities and grid operators have to get on board. Some are already understanding the benefits of tapping into V2X to access large energy resources without having to build or maintain sites. Many utilities are now familiar with virtual power plant (VPP) programs, so they just have to add EVs as an accessible option. V2X software will allow this to happen.
Fermata has been getting utilities comfortable with its V2X capabilities for the last few years. The company’s V2X software is allowing an EV used by Burrillville, Rhode Island, city employees to send power back to National Grid for compensation through the ConnectedSolutions program.
Bidirectional charging opens up many energy-saving possibilities for both homeowners and grid operators. The next few years should bring rapid advancement in both technology and regulations to allow this V2X interactivity to flourish.