Circle E- The encircled E means this bulb meets Federal minimum efficiency standards.
Footnotes Fluorescent/CFL 2
Econ-o-watt® lamps are only recommended for use on high power factor lead, indoor ballasts that meet ANSI standards. The lamps are not recommended for use in drafty areas, or locations where the ambient temperature is less than 60°F, except as noted. Also they should not be operated on low power factor ballasts, reduced light or reduced current ballasts, dimming ballasts or emergency system inverter ballasts. (214)