I did some of my own investigation and this is what I concluded:

1.  you can generate 1 MW over 7 days but you need to provide 2 liters of water per hr.  or 2 x 168hrs = 336 liters of water.

2. the best electrical electrolyses processes require more energy to produce the hydrogen (about 70% efficiency)

3. is it electricity which is used to breakdown the water?????

4. calculations

1 kg of hydrogen (which has a specific energy of 143 MJ/kg or about 40 kWh/kg)

Based on the atomic properties of water, 1 kg of hydrogen gas requires about 2.4 gallons of water as feedstock

2.4 gallons = 9.1 liters

1 Mega Watt of energy over 7 days for 2 liters of water?

2 liters of water will yield (1 kg x 2/9.1) = 0.22 kg of hydrogen

0.22 kg of hydrogen will yield (0.22kg x 40 kWh/kg) = 8.79 kWh

MJ  -   143 x 8.79/40  = 31.81 MJ

7 days is 168 hrs

7 days of energy yields  8.79 kWh  or  1.4 Mega Watt for the total 7 days  100% efficiency

Yes you can get 1MW of power over 7 days at a rate of 8.79 kWh  using 2 liters/hr of water to produce 0.22 kg of Hydrogen per hr