From Unidirectional to Bidirectional: Understanding the Role and Value of Managed Charging

EV sales have hit record highs over the past year and are slated for continued growth in 2024 and beyond (Bloomberg, 2024). At high rates of adoption, these EVs can have significant impacts on coincident-system and feeder-level peaks. In preparation for this adoption, utilities across the U.S. have been implementing managed charging programs to optimize EV charging and mitigate grid impacts (SEPA, 2021). Managed charging is an umbrella term for the implementation of any passive or active strategy that optimizes EV charging. Managed charging can include:

• Charging a vehicle outside of a utility’s peak times
• Dynamically charging the vehicle in response to market signals
• Scheduling EV charging to coincide with periods of high renewable energy supply
• Reducing EV charging rates to limit load congestion at site and feeder levels
• Pausing and/or reducing EV charging to reduce a site’s or feeder’s peak demand
• Creating efficient charging schedules for fleets
• Using bidirectional charging to support customer and grid needs

Managed charging solutions can greatly benefit grid operations by maximizing the value of local generation, harnessing lower time-of-use (TOU) rates, and reducing on-site equipment upgrades. Part of the value of managed charging is determined by how the EVSE is controlled (Figure 1). Passive managed charging depends on customer behaviors and cooperation, whereas active managed charging, including bidirectional charging, relies more heavily on advanced software systems and smart devices to control EV charging. As more utilities, fleet operators, residential customers, and other entities have adopted more advanced managed charging applications, this development has set the stage for the adoption of bidirectional charging.

Figure 1. The Stages of Managed Charging.

Source: SEPA. (2023).

Discussions with utility subject matter experts (SMEs) reveal a nuanced understanding of bidirectional charging as an evolutionary step within their managed charging initiatives (SEPA, 2023). Several SMEs indicated that they viewed bidirectional charging as a continuation of their managed charging programs and could see themselves adding a bidirectional charging program as a later phase to those programs. Sixteen of the thirty-seven utility SMEs stated that they had a program that actively manages EV charging (as opposed to a passive TOU program or no program at all) (Figure 2). Four of these utilities had already expanded their demand response managed charging program to include bidirectional charging or had developed a separate bidirectional charging pilot.

Figure 2. Utility Respondents with an Active Managed Charging Program.

Source: SEPA. (2023).

Many of the SMEs indicated that they wanted to learn how to manage EV charging and its interaction with their grid before transitioning to bidirectional charging. While bidirectional charging can unlock more value from EVs, managed (unidirectional) is also critically important. As seen in both the 2021 and 2023 State of Managed Charging reports, many utilities are still at the beginning of their managed charging journeys and are determining the value managed charging has on their grids. As utilities understand managed charging, they can apply these learnings to its next evolution in bidirectional charging.

Utility Program Design- Managed Charging’s Influence on Bidirectional Charging

Utilities are in the early stages of determining compensation structures for customers participating in bidirectional charging programs (Table 1). However, utilities are already using existing managed charging programs (such as demand response programs) to inform their bidirectional charging programs. Utilities can leverage managed charging incentives to design incentives for bidirectional charging programs. Common managed charging programs and their incentives include:

• Rebate programs that cover the cost of the charger and/or a portion of a customer’s panel upgrades. Utilities often require customers receiving the rebate to register their EV in a demand response, TOU program, or other type of managed charging program.
• Whole-home and EV-specific TOU programs that incentivize customers to charge during non-peak times.
• Demand response programs that incentivize customers to participate in demand response events and often have requirements for customers to participate in a minimum number of events during the peak season.
• EV specific rate structures that incentivize customers to charge at beneficial grid times and allow utility control of their charging. (See the blog “Set it and Forget it” for more details on these types of programs)

Utilities structure these programs to reflect the value that the EV resources provide the grid and to compensate customers for that value. Utilities identify that value by:

1. Determining the service they want EVs to provide and determine if other resources currently provide that same service. For example, if a utility wants an EV to discharge to the grid during peak times through a demand response program, the utility would examine how other resources (such as stationary batteries) are valued in that program.
2. Evaluating to what extent EV participation would provide the same service as other resources and if the EV participation has the same degree of reliability and performance.
3. Applying the existing or modified compensation mechanism to the managed charging program where applicable.

Utilities are in the process of determining how they want to use EV discharging for provision of grid services and how EVs compare to other resources. Currently, there are few examples of utilities compensating customers for discharging their EVs (Table 1).

Conclusion

As bidirectional charging garners attention for its potential to change EV usage, it is imperative to maintain a balanced perspective by acknowledging the enduring value of managed charging. A comprehensive strategy that integrates both bidirectional charging and managed charging – including passive and active types –  is crucial for resilient and efficient EV infrastructure. By navigating this dual approach, utilities and stakeholders can future-proof their initiatives, ensuring a seamless transition to a sustainable and optimized electric vehicle future. While bidirectional charging has significant potential in transforming how consumers view and use their EVs, there are still many challenges that must be addressed to capture this value at scale. In the interim, utilities, fleet operators, and other stakeholders can look to managed charging to capture beneficial grid impacts and savings. Look out for SEPA’s upcoming State of Managed Charging in 2024 to learn more about how managed charging can benefit the distribution system and provide savings to customers and utilities alike.