Two decades of vehicle-to-grid research show widely divergent profitability estimates

The global electric vehicle fleet already stores more energy than all dedicated grid-scale batteries combined, yet this capacity remains largely untapped. Vehicle-to-grid could unlock it, but only if participation is profitable for vehicle owners. In this review, we harmonize 680 outcomes from 86 modeling studies to assess the profitability of vehicle-to-grid. We classify each article by the market segment generating vehicle-to-grid revenue, the model linking vehicles to that market, the point in the value chain the reported value describes, and the underlying modeling assumptions. Reported profitability estimates range from net losses to several thousand euros per vehicle, and most describe the value realized in the market rather than what a vehicle owner retains. The median study reports 201 EURper EV per year and 86% report a gain, yet study medians span more than an order of magnitude. Within individual studies, profitability increases with deployable flexibility and decreases with cycling costs. However, these relationships are obscured across studies because key design choices (including cost scope, market environment, and vehicle availability) vary simultaneously and cannot be disentangled. Genuine market heterogeneity and differences in modeling realism therefore co-vary and cannot be separated with the available evidence. At the same time, the conditions for profitability are improving, driven by falling battery prices, lower-than-assumed real-world degradation costs, and regulations beginning to recognize bidirectional storage. The question is no longer whether vehicle-to-grid can be profitable, but under which market and regulatory conditions it can scale.