The provision of ancillary services in the smart grid by electric vehicles is attractive to grid operators. Vehicles must be aggregated to meet the minimum power requirements of providing ancillary services to the grid. Likely aggregator revenues are insufficient to cover the additional battery degradation costs which would be borne by an existing electric vehicle owner. Moreover, aggregator revenues are insufficient to make electric vehicles competitive with conventional vehicles and encourage uptake by prospective consumers. Net annual costs and hourly compensation payments to electric vehicle owners were most sensitive to battery cost. The fleet provided firm fast reserve from 1900 h for 0.42 h, up to 2.7 h in the best cases. At best, likely aggregator revenue was 20 times less than the compensation required, up to 27,500 times at worst. The electric vehicle fleet may not be large enough to meet the firm fast reserve power and duration requirements until 2020. However, it may not be until 2030 that enough vehicles have been sold to provide this service cost-effectively. Even then, many more electric vehicles will be needed to meet the power level and duration requirements, both more often and for longer to enable participation in an all-day, everyday ancillary services market.