Energy Saving Lightbulbs

Energy saving lightbulbs generally come with one of the five following fittings (also referred to as bases or caps) which match the traditional incandescent light bulbs they were designed to replace:

The most common fitting in the UK, the Bayonet Cap is fitted by pushing the bulb into the light socket and then twisting it until it locks into place.

Small Bayonet Cap (also referred to as SBC or B15)

A smaller version of the Bayonet Cap, frequently used for energy saving candle bulbs.

Edison Screw (also called ES or E27)

Named after the famous American inventor and entrepreneur Thomas Edison, the Edison screw is used worldwide and is growing in popularity in the UK due to the increase in imported lamps and lights.  As the name suggests, this bulb screws into the light socket.

Small Edison Screw (often referred to as SES or E14)

A smaller version of the Edison Screw, also used for energy efficient candle bulbs.

GU10

This is a common fitting for the type of spotlights you find in kitchens and bathrooms.  The U in GU10 stands for universal, and that’s because a bulb with a GU10 base can also fit a GZ10 socket (unfortunately it doesn’t work the other way round though).