It might say the actual power draw on the back of the LED, or if it has a brand name google it and read the small print.
Other than that get a kilowatt meter as suggested so you know what you have.
It could be anywhere from 130-240w .
If you have the height you could hang it above and use some of your cfl as side lighting up close.
You might find with cfl the plants don't stretch much, a bit of stretch when you flip to flower would be beneficial to your yield and the LED would have them stretched out more.