What Is an Equivalent of a 13 Watt CFL?

A CFL bulb uses much less energy than an incandescent bulb because very little of the electricity used to excite the mercury atoms inside is wasted as heat. In the traditional incandescent lightbulb, up to 90 percent of the electricity is wasted as heat, which explains the much higher power usage to obtain a similar output of light. An LED uses the least energy of the three options.