Meh, net gain is the point, long cycles well be useful for production. Useful, eventually. Cart before the horse, otherwise.

I'm studying Physics at the moment and Prof. gave us a printout of a textbook last week stating that the internal of the sun generates approximately 150 W / m³ on average. That's about as much as a compost pile, so, not very much. The sun only generates enormous amounts of power because it's so huge. In other words, reproducing fusion on Earth might actually not be very efficient.

0 theoretical hope for fusion energy to ever provide electricity under 30c/kwh. These are hot plasma experiments, which could be used to produce mass HHO from water vapour at just 2200C-3000C, even if endothermic. Can get energy from concentrated solar mirrors or just PV solar if plasma is used. Cooling magnets is a huge energy drain. HHO provide the highest turbine energy gain, though a net gain pathway is just slightly more in reach than fusion.