Flow batteries have the potential to provide ancillary grid services such as area regulation. In this paper, a hypothetical 2 MW flow battery is simulated in an area regulation application to find the optimal energy-to-power ratio that maximizes the net present value (NPV) of a 10 year project based on a range of installation costs. Financial and operational results are presented, and candidate battery chemistries are discussed. A simplified model of battery installation costs (dollars per kW h) resulted in a positive NPV for installation costs below $500 kW−1 h−1. For installation costs between $300 and $500 kW−1 h−1, an optimal energy-to-power ratio is 1.39. The traditional advantage of decoupling power and energy capacity may not be realized in area regulation; therefore hybrid flow batteries may be more appropriate. Zinc-bromine and iron-chromium chemistries might fit well with this application, along with lower-cost flow battery chemistries in the future.