[Anthony]

The whole business with kWh is an attempt to be consistent with ultratech power cells -- in 3rd edition, since 4th edition power cells have no defined energy content. In any case, the actually important conversion is that a power source suitable for spellcasting must be able to provide 360 kW (0.1 kWh/s) per point of fatigue, for at least 1s. This basically means that the vast majority of familiar power sources (e.g. household power) are totally useless for draw power, and even exceptions (such as the drivetrain of a 500 horsepower car) are something like 1 fatigue. Basically, to make draw power useful at TL 8, you'll want something like a flywheel or compulsator, and even then you're talking 100+ pounds of hardware per point of fatigue you can draw from it.