The paper assesses the impact of electric-drive vehicles (EDVs) on power system reliability. For this purpose, it introduces direct optimization of reliability indices LOLE (Loss of Load Expectation) and EENS (Expected Energy Not Served). The analysis is performed by the proposed optimization model applied in different strategies of charging/discharging of EDV batteries. In general, it is observed that numerous EDVs increase the system loading resulting in weakening of the system reliability. However, the paper comes to the conclusion that EDVs could support the system to some extent, depending on the penetration level of EDVs, if an appropriate charging/discharging strategy is applied. Besides this technical question the paper also addresses the costs of the system reserve provision required for the system reliability support. A system operator could engage additional power plants in order to maintain the system reliability or, if this is more cost effective, the support could be provided by EDVs applying the appropriate charging/discharging strategy. The paper proposes a new approach for the techno-economic assessment of possible solutions that are ranked by its price-performance ratio. (C) 2015 Elsevier Ltd. All rights reserved.