OK, now I have to chime in.
       If the combustion of hydrogen and oxygen gave off more energy than it
takes to separate the hydrogen and oxygen from water, then there would be no
energy crisis in California or anywhere else.  The world would be a different
place.  Engineers would be able to make a tiny engine out of a few drops of
water, that would continuously be split and rejoined, providing endless
amounts of energy.
       The simple fact that electrolysis has been thoroughly researched (and
taught in every high-school science class) and the current level of
technology is very high, and yet these water engines do not exist, should
indicate to the non-scientist that you cannot extract more energy from water
than you put into it.
       I understand the laws of thermodynamics.  Perhaps others don't.  But
beyond the academic aspect of it, the proof that this doesn't work is that
electrolysis isn't used as a power source.  Yes, hydrogen is used as a fuel,
but it is manufactured at a cost.   The hydrogen is only used as an
intermediary to transfer energy.  You cannot get something for nothing.  Even
if burning H and O2 made a minute amount of additional energy over
electrolysis, it would be the biggest thing ever.  Free energy!!  Perpetual
motion!!  Even if the reaction broke even (energy-wise), the dissipative
forces like friction and radiated heat would tip the balance.
       It is a nice thought, though, imagining a world with endless energy
supplies.

Bill Marshall
85 GL Tiico with many oxygen-related chemical reactions on the body