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The torque coefficient is derived from the power coefficient simply by dividing by the tip speed ratio, and so it does not give any additional information about the turbine's performance. The principal use of the C_Q – λ curve is for torque assessment purposes when the rotor is connected to a gearbox and generator.

Figure 3.53 shows how the torque developed by a turbine rises with increasing solidity. For modern high‐speed turbines designed for electricity generation, as low a torque as possible is desirable to reduce gearbox costs. However, the multi‐bladed, high solidity turbine, developed in the nineteenth century for water pumping, rotates slowly and has a very high starting torque coefficient necessary for overcoming the torque required to start a positive displacement pump.

The peak of the torque curve is at the stall onset and occurs at a lower tip speed ratio than the peak of the power curve.