Yes, you are almost right in your calculation but not forgetting when you run LED, the rating given by the manufacturer is base upon running on full power 100% intensity for all color spectrum which mean during the dimming up or down period the power consumption of the led will be lesser depending on your light setting as well. The only way to be able to measure the exact electrical consumption for the LED is by the Watt meter . Whereas for T5 is just a straight forward On / OFF .
you can also use the electrical calculator here ; http://www.sgreefclub.com/forum/powerconsumption.htm