Active managed EV charging can cut peak charging loads on distribution feeders by up to 50 percent and allow the grid to serve roughly twice as many electric vehicles before utilities must spend money on infrastructure upgrades, according to a new study from The Brattle Group prepared for grid-edge flexibility solutions provider EnergyHub.
Real-world data from Washington State
EnergyHub and The Brattle Group announced the results of a study that used real-world electric vehicle data from an EnergyHub program in Washington State to quantify the grid reliability and cost savings benefits of active managed charging.
The trial is notable because it moves beyond modeling assumptions, drawing on actual vehicle charging sessions rather than simulated behavior.
The Brattle Group’s analysis shows that advanced optimization of EV charging can help utilities meet this challenge effectively by reducing local grid stress and minimizing wholesale market costs, while continuing to ensure customer charging needs are met.
What the numbers show
The report, Demonstrating the Full Value of Managed EV Charging, compared two active management strategies tested in a real-world trial against unmanaged charging and passive time-of-use (TOU) rates, finding that active managed charging reduces EV charging peaks by up to 50 percent by smoothing load at the service transformer and feeder levels, and can allow the distribution network to support approximately twice as many EVs before requiring upgrades.
The approach can defer primary and secondary distribution system upgrades by up to ten years , and saves up to $400 per EV annually in system costs.
Active managed charging also handles complex time-of-use rate schedules on behalf of customers, reducing their charging bills.
That combination of deferred capital spending and lower ratepayer costs addresses two of the most persistent obstacles utilities raise when projecting what a growing EV fleet will cost to serve.
The findings land as grid planners face mounting pressure over load forecasting. Load from a single EV can add thousands of kilowatt-hours annually to a household’s electricity consumption, and this new demand can materialize faster and with less notice than traditional loads.
Without coordination strategies, those spikes concentrate at transformer and feeder nodes in ways that force expensive, time-consuming hardware replacements.
The managed versus unmanaged gap
As EV adoption continues, utilities are tasked with managing increased strain on an aging grid. Utilities must anticipate when and where new loads will materialize to effectively manage EV growth and maintain grid reliability.
The Washington State trial illustrates what happens when utilities act on that intelligence rather than waiting for stress events.
The simplest form of EV managed charging is time-of-use pricing that offers lower electricity rates during off-peak periods. More sophisticated managed charging plans control charging based on a user’s travel needs and grid conditions.
The Brattle study compared two active management strategies tested in a real-world trial against unmanaged charging and passive time-of-use (TOU) rates , finding the active approach consistently outperformed passive rate signals on every grid metric measured.
Why planners are paying attention
In a scenario where 25 percent of annual vehicle sales are EVs, the lower peak loads from active managed charging allow planners to keep using existing equipment for a decade longer than they could under a passive TOU strategy. For a primary feeder, an upgrade might be needed at 14 percent EV penetration under passive TOU, but deferred until 31 percent penetration with active management.
Pushing those investments further into the future gives planners time to gather better demand data and deploy software controls before committing to costly hardware.
The grid load question is already reshaping how regulators and utilities approach transmission planning, with the DOE’s draft transmission study flagging surging load growth as the sector’s defining challenge.
Separately, battery storage developers are racing to build the flexible capacity that complements managed charging programs, as detailed in earlier GCN reporting on record grid battery installations.
The Brattle Group’s findings highlight the urgency for regulators and utilities to move from a policy of reactive infrastructure upgrades to proactive planning that incorporates grid-edge solutions. EnergyHub and The Brattle Group said the findings are designed to give utilities and regulators actionable data for planning decisions, rather than broad scenario forecasts.
With national EV fleet growth accelerating and distribution infrastructure aging, the $400-per-vehicle annual system savings figure is likely to attract close attention from state public utility commissions weighing the true infrastructure cost of electrifying transportation.
