Zero:
You need to tell me what is the water usage you have now and the water usage you like to have with the additional head.
The losses depend on the water flow, and normally, the best water flow is 2/3 of the static pressure.
Static Pressure for 25 meters is 35.5 PSI so 2 / 3 * 35.5 = 23.7 PSI which represents 16.7 meters head and the optimal velocity = sqroot( 2 * 16.7 * 9.81 ) = 17.5 meters / sec.
The maximum flow = PI * R^2 * Velocity = 3.14 * 0.025^2 * 17.5 m/s = 34 l/s
Now how much water are you using.
I have data for pressure drop based on l/s that can as well calculate the available power, though not close to me, it may take a couple of days to get it.
If you need further assistance contact directly
Regards
Nando
nando37 at comcast dot net