Calculating fluorescent light load is the same as calculating the light load for incandescent or halogen lamps and is done by measuring the wattage. The main difference is that the fluorescent lighting uses only a quarter of the power to create the same amount of light as the other kinds of bulbs, so you can run four times as many lights on the same circuit.
Make a list of all the fluorescent lights in the house.
Determine the wattage of each of the bulbs on the list. On tube lights, you can find the wattage on the bulb itself. On compact fluorescent bulbs (CFLs), the wattage is listed on the ballast, the plastic fixture on the base of the bulb.
Add up the wattage of all of the fluorescent lights on the list to determine the total load of the lights. That load would be four times as high if you were using comparable incandescent or halogen bulbs.
Knowing the power load of your fluorescent lights can be helpful for two reasons. First, it can assist you in determining how it affects your overall electric bill. Second, it can be useful to know if you are analysing the capacities of your home's electrical circuits.