"Geoffrey Landis published a design for a concentrator system for an SPS which uses inflatables for the structure and mirrors. By themselves the collectors massed a mere 800 tons, with 35% efficiency PVs and 1 GW delivered to the ground @ 33% transmission efficiency"

So about 3 GW in Space?

if it takes around 8 kwh of energy per kg to turn water into LH&LOX, that's 375000 kg per hr [375 tonnes].
So, that's too big.
But if it will sell some of electrical power in space for $5 per kwh that would be cool. If it could sell 1% of it's power in space, at $5 kwh it would probably make more money from that than selling 99% it's power to Earth.

Where in space is Landis thinking of putting this thing?