Dust on incandescent bulbs and fixtures does not affect the amount of light available for use. When leaving the room for only 2 to 3 minutes, it will still save energy to turn off incandescent bulbs. Fluorescent bulbs use electricity more efficiently than incandescent bulbs and produce about four times as much light per watt. Although fluorescent bulbs are more efficient, they do not last as long as incandescent bulbs. It is not possible to add fluorescent lighting to your home without totally rewiring the existing fixtures.
Older dimmer switches save more energy than the new solid-state dimmer switches on the market today.
Check to see that student has explained the type of lighting in each room of the home. Thus the electricity is going more directly to produce light instead of heat. Incandescent bulbs - These bulbs use electricity to heat a tungsten filament in a vacuum until the filament glows. Thus electricity is used to produce heat. The light is from the glow of the filament.