Brooks Short - Tampa, Florida , Dec 14, 2005; 07:22 p.m.
There is no "ideal" watt/second power level for something as general as "indoor shoots".
I've used 3-4800ws power packs at full power for interior architectural shots on 100 ISO4x film. I've used 2 4800ws packs on full power with umbrellas, optical spots, fresnel spots together for food shoots on 100 ISO medium format digital backs etc...etc...
It all depends on the size and scale of your set or subject, the modifiers used on your lights, the ISO you're shooting with and the f-stop/depth of field and format size of film or digital capture.