Incandescent lighting is the most common type of lighting used in homes.
Incandescent lamps operate without a ballast. They light up instantly, providing a warm light and excellent color rendition. They can also be dimmed. However, incandescent lamps have a low efficacy (10-17 lumens per watt) compared with other lighting options and a short average operating life (750–2,500 hours).
Incandescent lamps are the least expensive to buy, but because of their relative inefficiency and short life spans, they usually are more expensive to operate.
The three most common types of incandescent lamps are:
Standard Incandescent Lamps
Known as the screw-in "A"-type light bulb, standard incandescent lamps are the most common—but most inefficient—light source available.
These standard incandescent lamps produce light from a tiny coil of tungsten wire that glows when it is heated by an electrical current.
Larger-wattage incandescent bulbs have a higher efficacy than smaller-wattage bulbs. However, a larger-wattage lamp or bulb may not be the most energy- or cost-effective option, depending on how much light is needed.
"Long-life" bulbs, with thicker filaments, are a variation of A-type bulbs. Although these bulbs last longer than their counterparts, they are less energy efficient.
Energy-Saving Incandescent (or Halogen)
Energy-saving incandescent—or halogen—lamps are a type of incandescent lighting that achieve better energy efficiency than standard incandescent A-type light bulbs.
Halogen lamps have a gas filling and an inner coating that reflect heat. Together, the filling and coating recycle heat to keep the filament hot with less electricity.
These lamps provide excellent color rendition. They also are considerably more expensive to buy than standard incandescent lamps, but they are less expensive to operate because of their higher efficacy.
Reflector lamps (Type R)—a type of incandescent lighting—spread and direct light over specific areas. They are used mainly for floodlighting, spotlighting, and downlighting.
There are two types of reflector lamps: parabolic aluminized and ellipsoidal. Parabolic aluminized reflector lamps (Type PAR) are used for outdoor floodlighting. Ellipsoidal reflector lamps (Type ER) focus light beams about 2 inches (5 centimeters) in front of their enclosure, projecting light down from recessed fixtures. Ellipsoidal reflectors are twice as energy efficient as parabolic reflectors for recessed fixtures.