Saturn V at take off had an equivalent power of 166GW. If that was electricity it would be around 2x the total capacity of all the power stations in the UK.
To nit-pick, that's comparing heat production with electrical power. If we assume the power stations are 50% thermally efficient (which is a bit optimistic) the power in "heat" terms of the power grid would then be about the same as the Saturn V.
Rocket engines are extremely efficient. Especially in vacuum, they can convert almost all the heat into kinetic energy of the exhaust jet. They're the most efficient heat engines we have.
I wonder if anyone's experimented with using rockets to charge something like a flywheel battery or reservoir for hydro power. A 777's engine puts out tens of megawatts using a less refined fuel than rockets use. What if you hooked a rocket full of RP-1 to a pump to haul water from a river to a dam? This is probably nonsense.
A 777 engine is actually far more fuel efficient than a rocket engine. Take a look at specific impulse [0] for different engine types. A rocket is optimised to be very light and to use its own oxygen supply. A normal jet engine can be heavier and use the air as an oxidizer. Much more efficient for power production in a CCGT.
Rocket engines are actually very efficient, especially in vacuum. Very high expansion ratios can be achieved that converts almost all the heat into jet kinetic energy.
