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.