9/15/2026

Much of the discussion around bidirectional charging has focused on the home. A vehicle sits in a driveway or garage, connected to a bidirectional charger that can provide backup power, participate in a utility program, or send electricity back to the grid during periods of high demand.

A new academic study published in the journal Energy Conversion and Management, “Assessing Bidirectional EV Charging for Employer Parking: A Case Study of the MAHLE chargeBIG Demonstrator in Stuttgart,” looks at a different setting: the workplace.

Researchers from the Stuttgart Institute of Human Factors and Technology Management, MAHLE New Mobility Solutions, MAHLE chargeBIG, and Munster Technological University examined how bidirectional charging could work in a large employer parking facility. Their case study used the MAHLE chargeBIG demonstrator in Stuttgart, Germany, a workplace installation with 101 EV charging points serving a 660-space company parking facility.

The study is important because workplace charging has a different operating profile than residential charging. Vehicles tend to arrive in the morning and remain parked for many hours before employees leave in the late afternoon. That creates a long window in which EV batteries can potentially be managed as flexible energy resources without interfering with drivers’ transportation needs.

What the Researchers Wanted to Understand

The researchers set out to determine whether bidirectional charging could make economic and operational sense under realistic workplace conditions rather than under idealized assumptions.

Much of the previous V2G literature has relied on assumed arrival times, departure times, battery states of charge, and vehicle availability. The authors identified this as a significant limitation because the value of V2G depends heavily on when vehicles are actually plugged in and how much flexibility drivers can provide.

Their goal was therefore to combine real charging behavior with actual site characteristics and evaluate how bidirectional charging could reduce energy costs, manage peak demand, improve solar utilization, and provide enough value to compensate participating EV owners. They also incorporated battery degradation into the analysis, an important consideration because the additional cycling associated with V2G is frequently cited as a potential cost or barrier to participation.

More Than 6,000 Real Charging Sessions

One of the study’s strongest features is its use of empirical workplace charging data. The MAHLE site recorded 6,425 charging sessions involving 413 individual users during 2023, and after filtering and consolidating the data for computational purposes, the researchers modeled 6,080 charging events representing 60 users. The data showed a recognizable workplace pattern, with most EVs arriving between approximately 7 and 8 a.m. and departing between 4 and 6 p.m. Importantly, vehicles spent considerably more time parked than they spent actively charging. Across the broader charging dataset, only about 43% of parking time was being used for charging, suggesting a substantial amount of idle plugged-in time that could potentially be used for managed or bidirectional operation.

The researchers then built a mixed-integer linear programming model that optimized vehicle charging and discharging in 15-minute intervals over an entire year. The model incorporated the company’s electricity demand, EV availability and state of charge, electricity prices, charging infrastructure, a 66 kWh stationary battery, on-site photovoltaic generation, battery degradation, grid constraints, and investment costs. Several scenarios were evaluated, ranging from conventional charging and smart unidirectional charging to different levels of bidirectional charging power and combinations of workplace chargers and demonstration vehicles.

Peak Shaving, Not Energy Arbitrage, Drove Much of the Value

One of the more interesting findings was what did not create significant value. The model allowed EVs to charge when wholesale electricity prices were low and discharge when prices were higher, yet the researchers found that pure energy arbitrage was not economically attractive under the conditions modeled, even with perfect knowledge of future electricity prices. Instead, much of the economic value came from using EV batteries to reduce the company’s peak electricity demand.

That distinction matters for the V2G industry. V2G is sometimes discussed primarily as a way to buy electricity cheaply and sell it back later at a higher price, but this study suggests that, at least for commercial and industrial customers, some of the strongest value streams may instead come from avoiding expensive peaks, managing building loads, and providing flexible demand response. In the main car park scenario, smart charging reduced total annualized costs by about 0.6% compared with conventional charging. Bidirectional charging increased the reduction to about 1.3%, while an 11 kW bidirectional configuration reduced costs by roughly 1.5%. Bidirectional operation also reduced peak load by as much as 3.6% in these scenarios.

The researchers found even larger benefits for some individual vehicles and demonstration configurations. Depending on the scenario and vehicle availability, average company savings ranged from approximately €211 to €893 per EV per year, while the highest savings associated with individual EVs reached more than €2,000 annually.

Vehicle Availability Matters More Than Battery Size

Another important finding was that the amount of time a vehicle was available at the workplace could matter more than the size of its battery. Vehicles that appeared at the company frequently provided more opportunities for peak shaving and flexible operation, and the study found that the number of days an EV was present at the workplace was strongly related to the amount of energy it could discharge and the value it could provide.

That has direct implications for V2G program design. Rather than simply recruiting vehicles with the largest batteries, workplace V2G programs may need to focus on drivers or fleets with predictable parking patterns and long dwell times. Company vehicles, employee fleets, and other vehicles regularly parked for much of the business day could therefore be particularly attractive resources. The study also found diminishing returns from continuously increasing charging power. Moving from 7.2 kW to 11 kW AC, or from 10 kW to 20 kW DC, improved flexibility and economic performance, but increasing DC charging power further to 30 kW produced relatively little additional benefit.

That suggests workplace V2G may not necessarily require extremely high-power charging infrastructure. In many cases, moderate bidirectional power levels combined with long parking durations may provide substantial flexibility.

Workplace Charging and Solar Could Be a Natural Combination

The research also examined the interaction between bidirectional charging and on-site solar. The authors found that bidirectional charging allowed the company to economically integrate more photovoltaic generation than conventional or smart charging alone. In one scenario, combining bidirectional charging with an additional 750 kWp of rooftop solar produced a 6.4-year payback period and reduced peak demand by approximately 19%. More broadly, the bidirectional scenario supported an economically optimized PV system roughly 400 kWp larger than the comparable smart-charging case, leading the researchers to conclude that the added flexibility from EV batteries can help companies better integrate renewable generation and increase self-consumption.

This is an especially relevant feature of workplace charging because employee vehicles are commonly parked during daytime solar-generation hours. The study itself focuses on using that flexibility at the commercial site, but it also highlights why workplace charging could become an increasingly important complement to residential V2G. Longer term, bidirectional EVs could potentially participate in multiple locations and applications over the course of a day, although that broader mobile-storage use case was outside the scope of this research.

What It Means for the Bidirectional Charging Industry

The study broadens the V2G conversation beyond the residential garage by showing how workplaces can offer several characteristics that are particularly well suited to bidirectional charging: long vehicle dwell times, predictable operating schedules, concentrated numbers of EVs, significant building loads, demand charges, and growing adoption of on-site solar. The results also reinforce an important lesson for the industry: the economics of V2G may depend less on maximizing the amount of energy discharged and more on when and where that discharge occurs.

A relatively small amount of energy delivered during a facility’s annual peak can be more valuable than repeatedly cycling a battery for wholesale energy arbitrage. That makes load profiles, tariffs, vehicle availability, and site-specific constraints central to determining where bidirectional charging will create value. The authors calculated break-even compensation values ranging from €0.66 to €1.78 per discharged kWh, representing the maximum amount a company could theoretically pay participating EV owners while remaining financially neutral under the modeled scenarios.

The results are promising, but the authors caution that the analysis represents an optimized case study rather than a guaranteed outcome for every workplace. The model assumes perfect knowledge of electricity prices, building load, solar production, and vehicle availability, while real-world forecasting errors would likely reduce some of the savings. The underlying charging data also came from a workplace where employees had access to very inexpensive charging, which may not reflect typical charging behavior elsewhere. In addition, the economics were strongly influenced by the site’s peak-demand charges, meaning the value of bidirectional charging could look different under other utility tariffs. The researchers also characterize their battery-degradation assumptions as conserv

Bidirectional charging at home will remain an important part of the V2G market, but if EVs spend eight or more hours parked at workplaces during the day, employer parking lots may represent another substantial—and still relatively underexplored—source of grid flexibility.