Thanks, I will try that long-averaging method.
I wondered about simply getting current (from a current sense resistor, we dont have many current probes, and they're always gone "walkies") on one channel of a scope, Vin (AC) on the other, and then multiplying them, and getting the time average of the multiplications which is the power.
-However, i hope i can find this in the yokagawa DL9140 scope manual.
Also, the problem is it will be in the AC line so will be alternate pos and neg, and so will average to zero.....so i have to hope the math function is easy to work out.