The output electric power output, P, of a hydropower plant generator is given by;
P = r x g x Q x H x n
where;
r = density of water (1000 kg/m3 for purely H20)
g = gravitational acceleration (9.81 m/sec2)
H = net head (height difference between the water levels at the intake and the tailrace minus all head losses in the headrace and penstock in meters)
Q = water flow rate (in m3/ sec)
n = overall efficiency of the generating equipment (turbine efficiency multiplied by generator efficiency which is approximately 0.65 to 0.8)