What is bidirectional EV charging?

       The installation of EV chargers is quickly becoming a must-have service offered by solar installers. As more solar manufacturers begin to produce EV products, solar contractors are more likely to have the necessary connections and knowledge to complete another electrical hookup in a garage. As customers seek additional revenue and backup-power options for their EV investments, bidirectional EV charging should open up new installation opportunities for contractors.

　　How a traditional, unidirectional EV charger works

　　Essentially, all pre-2023 EV chargers 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 various types, including Level 1 and 2 chargers as well as fast DC chargers. Level 1 and 2 chargers simply move power; the electric vehicle itself converts supplied AC power to DC power to charge the vehicle's battery. A fast charger performs the AC-to-DC conversion and delivers direct current to the vehicle.

　　How a bidirectional EV charger works

　　A bidirectional charger enables regular charging of an EV's battery as well as power export from an EV battery into a home or onto the grid. Vehicle-to-grid (V2G) and vehicle-to-home (V2H) power transfer is also referred to as vehicle-to-everything (V2E) (V2X).

　　This represents a significant 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 the power of an EV battery for purposes other than driving could change how customers and utilities think about solar and storage adoption.

　　"Under the hood of a Nissan LEAF are 4.5 Powerwalls, which come standard with leather seats and air conditioning. "The Ford F-150 Lightning has more storage value under the hood than the vehicle cost," said David Slutzky, CEO of V2X software developer Fermata Energy.

　　Bidirectional chargers are only now becoming available on the market. Only two bidirectional chargers had received UL 9741 certification as of early 2023. the standard that covers bidirectional charging equipment and includes functionality to export power to the grid: Fermata Energy's FE-15 charger and Siemens' Ford Charge Station Pro. However, a slew of other companies, including Wallbox and Enphase, are developing their own bidirectional chargers, so the market should be flooded with options in 2024 and 2025.

　　Because the technology in a bidirectional EV charger is far more advanced than that in a unidirectional EV charger, development has been slow. To allow for the AC-to-DC power exchange and back, a more powerful inverter must be installed. Because the dual power transfer generates heat, more fans and higher-rated enclosures are required. If the vehicle is to work with the grid, automatic transfer switches must be installed. Add in software developments to ensure that the consumer can use the charger like any other smart device and that the utility can access that power, and you've got a much larger and more complicated product to manufacture.

　　However, once more bidirectional chargers are UL-certified and available for purchase, solar contractors should have no trouble learning how to install the new product. They can install a bidirectional charger if they know how to install an ESS or even just a solar inverter.

　　What still needs to be done

　　The announcement by Ford that the 131-kWh battery inside the F-150 Lightning could be used as an emergency backup for homes has fueled interest in bidirectional charging. While a second use for an EV battery is still advantageous, the real benefit of bidirectional charging and V2X is interacting with the grid.

　　"Because of the Ford Lightning, most people today consider V2H as a backup power source. "That's going to change pretty quickly once people realize we can produce energy savings on our utility bills through grid parity," 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 to four years, the majority of users will be managing energy efficiency and savings during grid parity rather than just using during outages."

　　Utilities and grid operators must join forces to make this possible. Some people are already seeing the advantages of using V2X to gain access to large amounts of energy without having to build or maintain infrastructure. Many utilities are already familiar with virtual power plant (VPP) programs, so they only need to add EVs as an option. This will be possible thanks to V2X software.

　　Fermata has spent the last few years familiarizing utilities with its V2X capabilities. Through the ConnectedSolutions program, the company's V2X software and bidirectional charger enable an EV used by Burrillville, Rhode Island, city employees to send power back to Rhode Island Energy (formerly National Grid).

　　Bidirectional charging provides many opportunities for energy savings 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.