The Pelton Wheel needs a source of water in order to run.
If the head of water is known, along with the flow rate, then it is possible to find the best size of wheel to use, how fast it should rotate to obtain the maximum efficiency, and what power it is likely to develop.
The velocity in the jet can be estimated by using the known fixed head. The diameter of the jet can then be found from the known flow rate. A suitable wheel diameter can be chosen in relation to the jet can size; typically the wheel would have a diameter of 10 times that jet. The best speed of rotation may then be selected, such that the speed of the buckets is approximately half that of the jet speed.
The power delivered in the jet can be calculated from the speed and cross-sectional area. The power developed by the Pelton wheel will be less than this, in the ratio of the wheel's efficiency, which may be estimated by reference to the known performance of existing machines of comparable size and output.