This was tested on an asteroid base in 200.123. Asteroids have a 500-unit charge, by default, which is from the old power system. With new reactors placed on the asteroid, regardless of the reactor size, all factories pull from the same 500-unit power pull on each tick.
For debug purposes, it would be useful to add to the display module the power supply and power demand tags to see if power demands are being met of an entity that has no ship core (asteroid, planet, station).
As a side note, it would be nice if basic factories were self-powering (1power unit/tick--this would mean about 21 min to make a single block without external power) to eliminate game stars without a power beam. In fact, in the new power system, the power supply beam charges up factories far too quickly to be well-balanced and should just be done away with. +50 power is A LOT more in the new system than the old one.