Frequency control, as an ancillary service, is usually provided by generation reserves. In modern generating units the ramp rate limit can be selected; e.g. their ramp rate can be selected to be either normal or fast. In this paper, the impact of selecting the fast ramp rate of generating units on electricity price and its volatility is investigated in simultaneous scheduling of energy and primary reserve. Simulation results show that using this capability of generating units, results in reduction of both the electricity price and its volatility. While, in minimum load condition, this capability may not necessarily be effective, it will be very essential for peak load condition. The effectiveness of this capability for medium load conditions depends on the load value and the units committed.