It would require about 14 MWh to lift a single ship to the upper level

Calculating the approximate wattage to lift all that water 26m:

9.8 w/s * 200000000 Liters * 26 m /60/60/1000/1000

200 000 000 liters was reported on wikipedia as amount of water used.

Its a very crude calculation probably of by quite a bit.

It's allot of electricity but the cost of that electricity would be essentially nothing when compared to what they charge. So I don't know why they don't install massive pumps. Maybe they don't want to contaminate the lake with salt water, but you would get small amounts of salt water with the current system to.