Some guy did some great tests of 2-bulb 4' tube light power consumption
Comparison of Philips InstantFit T8 LED and Philips T8 Fluorescent: https://www.youtube.com/watch?v=enqAfX1pb80
T12 Fluorescent: https://www.youtube.com/watch?v=-RzAABBcduw
tl;dw:
T12 Fluorescent (2 bulbs) - 90W
T8 Fluorescent (2 bulbs) - 54W
T8 LED (2 bulbs) - 32W