In this episode, Ensign Kim and Seven of Nine are working in one of Voyagers conduits. The scene progresses as follows :
Seven : 'The optical assembly is properly aligned. I am ready to access the main power supply.'
Kim : 'After you.'
[They climb down to a lower level. Seven opens a panel and begins to reach inside. Kim pulls her back hurriedly.]
Kim : 'Wait! What are you doing, there are five million gigawatts running through there!'
Seven : 'The exoskeleton on this limb can withstand it.'
At this point Voyager is proceeding on impulse, and is not using any high power systems. This gives us a minimum figure for Voyagers total power output of 5 x 103 TeraWatts.
We are told in Caretaker that Voyager has a maximum sustainable cruise speed of Warp 9.975. On the Galaxy class starship total output calculations, I worked out how much power it takes to drive a GCS at various warp speeds. No solid figures are available for a velocity of warp 9.975, but at warp 9.9 a GCS consumes some 6 x 1020 Watts. Voyager masses 700,000 tons compared to the 5 million tons of the Galaxy class; we do not know how the mass of an object affects the power required to maintain a given speed, but to make a guestiumate I will assume it is a linear relationship. The power required for Voyager to maintain Warp 9.9 would be given by :
P = (7 x 105/5 x 106) x 6 x 1020
= 0.14 x 6 x 1020
= 8.4 x 1019
Or 84 million TeraWatts. Given the way power requirements increase as one nears warp ten, it is likely that warp 9.975 requires at least a tenfold increase in power over warp 9.9. Therefore, Voyagers maximum power output is likely to be in the region of 108 TeraWatts or more.
The Revulsion dialogue is the only clear reference to Voyagers power output I've been able to find so far. Although it is far lower than the million-plus terawatt figures calculated for the Galaxy class, you wouldn't expect a starship travelling on impulse to be using maximum power. In addition, this figure is the power running through that particular conduit - which is not necessarily the whole of the main power output.
Calculatiuons based on warp speeds indicate that Voyager has a maximum output roughly equal to that of a Galaxy class, despite her much smaller size. This seems reasonable given that she is more advanced, and so much faster.