Converting calories to Joules gives us a total of approx. 2600 joules of energy. For fresh water, it takes quite a large voltage to drive a big current through the water, and the bigger the current, the faster the boiling is accomplished. This is quite a large, expensive capacitor. ESJ This was part of Dr. Graneau's research into unexplained forces in fluid conductors, and he suspects that electrical water explosions are not simple boiling, but may be some sort of motor-force effect.
Some researchers report neutron bursts from capacitor discharges through water or ice.
Also see my article on capacitor discharge demonstrations. Take the warnings seriously, this stuff is as dangerous as working with high explosives. All rights reserved.