Energy-saving light bulbs, primarily and CFLs (Compact Fluorescent Lamps) , represent a major shift from traditional incandescent bulbs by converting electrical energy into light rather than heat. While an incandescent bulb loses up to 95% of its energy as heat , modern LEDs use up to 90% less energy to provide the same level of brightness. Comparison of Popular Bulb Types Lighting Choices to Save You Money - Department of Energy