Known as the screw-in 'A'-type light bulb, standard incandescent lamps are the most common – but the 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 these A-type bulbs. Although these bulbs last longer than their counterparts, they are less energy efficient.