November 18, 2025
Negative Electric Vehicle Emissions: Vehicle-to-Grid Can Incentivize Enough Wind and Solar Investment to Reverse EV Charging Emissions, by Jiahui Chen, Michael T. Craig, Jeremy Michalek, Matthew Bruchon, and Parth Vaishnav. Published in Environmental Science & Technology (2025).
A Note from Steve
When I co-authored one of the first academic papers on vehicle-to-grid technology with Dr. Kempton back in 1997, the central idea was that electric vehicles could become dynamic assets for a renewable energy grid, storing wind and solar power when it’s plentiful and returning it when it’s needed most. Nearly three decades later, it’s deeply rewarding to see rigorous, data-driven research confirming that early vision. What was once a theoretical possibility is now an emerging reality, one that validates the promise that first drew me to this field and continues to drive my work today.
Electric vehicles have long been championed as a cornerstone of the clean energy transition, but their environmental story has always come with an asterisk: EVs eliminate tailpipe emissions, yet they still depend on the power grid, which may rely heavily on fossil fuels. A new study from researchers at the University of Michigan and Carnegie Mellon University turns this narrative on its head, showing that bidirectional charging using vehicle-to-grid (V2G) technology could do far more than simply shift emissions from tailpipes to smokestacks. It could make them go negative.
In the article Negative Electric Vehicle Emissions: Vehicle-to-Grid Can Incentivize Enough Wind and Solar Investment to Reverse EV Charging Emissions, Jiahui Chen and colleagues provide one of the most sophisticated examinations yet of how electric vehicles interact with power system evolution. Their finding is as bold as it is consequential: if EVs charge flexibly and participate in V2G programs, they can create strong economic incentives to build additional wind and solar capacity, enough to more than offset the emissions produced from charging. In short, EVs could become a driver of grid decarbonization rather than simply a new source of demand to be managed.
Modeling a Dynamic Grid
The researchers used a highly detailed unit commitment and economic dispatch model of the PJM Interconnection, the largest grid operator in the U.S., and a proxy for the North American grid mix. Most studies of EV-grid interactions stop at short-term operational impacts, how and when vehicles draw power. This one goes further, capturing how those charging patterns influence long-run investment decisions in new sources of power generation.
Three charging behaviors were modeled for a fleet representing ten percent of PJM’s light-duty vehicles. In the uncontrolled charging case, vehicles begin charging immediately after their last daily trip. The cost-minimizing charging case assumes smart scheduling that shifts load to lower-cost hours. The V2G scenario allows bidirectional power flow, enabling vehicles to both charge and discharge energy depending on grid conditions. Each case was evaluated under multiple levels of wind and solar penetration, and the model was used to determine how profitable additional renewable investments would be under each charging regime.
The study also incorporated real-world driving behavior from the National Household Travel Survey, regional generation data, and emission factors from the EPA’s National Emissions Inventory. External costs were monetized using a social cost of carbon of $204 per ton of CO₂-equivalent and the AP3 air pollution model to account for mortality impacts from local pollutants.
Charging Strategy Determines Climate Impact
The contrast among the three scenarios is striking. When EVs charge without coordination, the added demand is largely met by existing fossil generation, primarily natural gas and coal. In this uncontrolled scenario, total power system externalities increase by roughly $330 per vehicle per year, and incentives to invest in new renewable capacity are negligible, with only about 300 megawatts of additional wind or solar capacity across the PJM region. In other words, unmanaged EV charging simply deepens the grid’s carbon footprint.
When charging is optimized to minimize costs, however, the story changes. Shifting load to off-peak periods increases the value of wind and solar generation by allowing those resources to operate more fully and with less curtailment. Under this flexible, cost-minimizing scenario, the study found a 4 percent increase in profitable wind and solar investment, about 2.8 gigawatts of new capacity, and a reversal in emissions impact. Accounting for the resulting capacity expansion, total grid emission externalities fall by $230 per vehicle per year.
Adding V2G capability amplifies this effect dramatically. By allowing vehicles to discharge electricity back to the grid during peak periods, V2G acts as a distributed storage network, reducing curtailment, raising renewable revenues, and displacing high-emission peaking plants. The model shows that V2G could boost wind and solar investment by 23 percent, an additional 15 gigawatts of renewable capacity, and turn EV charging into a net environmental benefit. Once these induced investments are accounted for, V2G reduces total power system emissions externalities by approximately $2,200 per vehicle per year.
System-Level Benefits and Robustness
The economic implications are just as powerful. Relative to a system with no EVs, V2G reduces total system costs by about 13 percent, translating to roughly $880 in annual savings per vehicle. Flexible one-way charging (V1G) delivers more modest benefits, lowering system costs by about $400 per vehicle per year. Sensitivity analyses confirm that these gains hold across a wide range of conditions. While greater stationary storage capacity reduces the marginal value of V2G—because vehicles compete with utility-scale batteries for the same flexibility services—the overall effect remains strongly positive. Doubling transmission capacity amplifies V2G’s benefits by allowing additional renewable generation to reach load centers, while doubling EV penetration slightly reduces per-vehicle savings but preserves substantial system-level value.
Importantly, the core findings remain robust even under conservative assumptions about renewable costs, grid mix, and EV participation. Still, the authors acknowledge several limitations. The analysis assumes highly coordinated charging and discharging across millions of EVs, levels of control not yet achievable in real systems, and does not explicitly account for potential costs from battery degradation or bidirectional hardware upgrades. The model also treats wind and solar expansion as purely economically driven, sidestepping siting constraints, interconnection delays, and policy hurdles that often slow renewable deployment. And because the study focuses on PJM, the magnitude of benefits may differ in regions with higher renewable penetration or different generation mixes. Even with these caveats, the directional takeaway is clear: managed charging and V2G can materially accelerate clean energy investment and reduce emissions when deployed at scale.
Implications for the V2G Industry
For the V2G industry, this research provides rigorous, quantitative confirmation of a long-standing hypothesis: EV flexibility doesn’t just balance the grid, it transforms it. When vehicles can both absorb excess generation and discharge during peaks, they change the investment calculus for renewables. Every plugged-in car becomes part of the infrastructure that makes wind and solar more profitable, accelerating their deployment.
This insight has far-reaching policy and market implications. It strengthens the case for incentivizing flexible charging and bidirectional participation through utility programs, rate designs, and capacity markets that recognize the system-level value of vehicle flexibility. It also highlights the importance of continued progress on standards and interoperability, particularly communication protocols like ISO 15118 and interconnection certifications such as UL 1741 SB and SC, to enable aggregated coordination at scale.
Perhaps most importantly, it reframes the debate about EVs and the grid. The question is no longer whether EVs will strain the power system, but how their flexibility can be harnessed to decarbonize it faster and at lower cost. As the authors conclude, “leveraging flexibility in charge timing and V2G to reduce power system costs can also produce substantial emission co-benefits.”
