Standard tungsten incandescent light bulbs (your standard domestic light bulb) are generally pear shaped and burn electricity to heat a filament until it glows white and produces a bright light. Approximately 90% of the electricity used to power regular light bulbs is lost to heat and you can expect the burn time to be 800 – 1000 hours before expiration. These bulbs have a poor luminous efficacy, typically 10 -13. Efficacy is the ability of a lamp to convert electrical energy into light energy. The higher the efficacy the more efficient the bulb.
In a drive toward more energy efficient lighting from 30th August 2009 it became illegal for retailers to import 100W, frosted or pearled incandescent light bulbs, or to sell them once their current stocks have run out. From September 2011, 60W clear incandescent bulbs will be banned, followed by a ban on all remaining incandescent bulbs in September 2012.
The aim is to switch people as quickly as is feasible to more energy efficient compact fluorescent lamps (CFLs), which consume a fifth of the energy used by old-style bulbs. It has been calculated that if every British household were to replace three 60 or 100 watt light bulbs with CFLs the energy saved would exceed the power used by the country’s entire street lighting network.