I would post an example, but I'm using 7.1 and I'm not sure what would happen. Try obtaining your samples in the for loop (I couldn't run your vi, or really understand it, since I didn't have any of the sub vi's), and wiring the output of the sub vi that gets the output from the meter to the edge of the loop, and auto-index it. From there, use a math function to sum the array (Numeric-> Add Array Elements), and simply divide by the number of loop iterations.
To find the power consumed, I assume you either know the current drawn or are getting it the same way you did the voltage, and simply multiply the current by the voltage. To get power in watts anyways. Hope this helps.
Geoff