As bidirectional EV charging grows, utility group suggests requiring interconnection

Interconnection of bidirectional EV chargers can enable grid compensation for EV owners while enhancing safety, says a report that offers comprehensive guidance for regulators.

The Smart Electric Power Alliance has issued a report advising regulators how to prepare for broader customer adoption of electric vehicles and EV chargers capable of exporting energy from the EV battery to the grid.

At least eight states are developing approaches to energy export from electric vehicles or electric buses, which can help balance renewable generation in the same way as stationary battery storage.

The SEPA report focuses on residential bidirectional EV charging, saying now is a good time for farsighted regulation.

“While customer adoption is low, regulatory commissions have the opportunity to lay the regulatory groundwork that will support integration of these systems with the utility grid and provide customers compensation for participating in grid services,” the report says.

SEPA recommends developing more precise regulatory language than the terms used by marketers, such as vehicle-to-home, backup, or vehicle-to-grid. It suggests three technical definitions:

• “Non-parallel” for a bidirectional charging system that discharges only when the customer’s site is disconnected from the grid
• “Parallel, non-exporting” for a system that offsets a customer’s energy use during high-load periods, with no electricity transferred across the customer’s meter to the grid
• “Parallel, exporting” for a system that sends electricity in excess of a site’s load back to the grid.

Using such definitions will clarify, for example, whether a customer may power their home with an EV during power outages “under existing energization rules, or are required to undergo an interconnection process,” SEPA said, adding that even energization “still requires appropriate software and hardware safeguards to prevent backfeeding” of energy to the grid.

Requiring a full interconnection process, SEPA says, “enables utilities to ensure safe installations” and can enable grid export compensation to EV owners, the use of dynamic rates, and integration of EV batteries into virtual power plants. The report makes a case for mandating that all bidirectional charging systems interconnect.

Looking ahead, SEPA says that while most bidirectional installations in the U.S. to date have used an “off-board” inverter, integrated into the EV charger or a separate backup system, that converts the battery’s DC power to AC power, more vehicles with “onboard” DC-to-AC inverters may be manufactured in the next five years.

“Moving the inverter on-board will likely decrease the total cost of bidirectional enablement and accelerate adoption,” the report says, but vehicles on the road today “will still need pathways for interconnection and interaction with the grid.”

Staff from ten utilities provided input to the report, as did experts from vehicle and charger manufacturers, software providers and nonprofits.

SEPA’s report is titled “Interconnection guidance for residential bidirectional EV charging: A utility-informed resource for regulators.”