CFL bulbs are ideal for smaller grow spaces as they emit less heat than the more it's HPS and MH light counterparts. Each bulb has it's own built in ballast, make sure you have a compatible light reflector as it is a different connector to the HID lights.
 
This bulb is 250w and in the blue spectrum which plants crave during their vegetive stage. It is common practice to use a CFL for cuttings and seedlings before transfering them to a more intense light once they are established.