What is an E27 GLS bulb?

An E27 GLS bulb is one of the most common types of light bulbs used in homes, offices, shops, and commercial buildings.  They are commonly found in light fittings across the UK and in Europe. The term “E27” refers to the fitting type and the term “GLS” refers to the shape of the bulb. These terms together describe a standard screw-fit bulb that has a traditional pear-shaped design that is widely used for general lighting purposes.

The “E” in E27 stands for Edison Screw.  It refers to the fitting type of the bulb and in this case it is a screw shaped base measuring 27mm in diameter.  The design is named after Thomas Edison, who helped to develop the screw-type bulb base.  These facts in combination with each other give us the figure E27 as a means of identifying this type of bulb.  It is the standardized large screw cap used in many ceiling lights, table lamps, floor lamps, wall lights, and pendant fittings. 

GLS stands for General Lighting Service.  This term describes the classic bulb shape most people would associate with the image of a traditional household light bulb.  It has a rounded top with a wider body that tapers down towards the base. This design allows it to have a wide light distribution and makes it suitable for everyday room lighting over focused spotlighting.  GLS bulbs are commonly used to give an even illumination across a full room.

The E27 GLS bulb design has been used in several lighting technologies.  This includes incandescent, halogen, CFL (compact fluorescent), and LED bulbs.  LED E27 GLS bulbs have become the preferred option of this type of light for many people as they use far less electricity, last much longer, and produce less heat than older types of bulb technologies.  To give an example - a modern LED E27 bulb using 8 to 10 watts of electricity would be the recommended equivalent for a traditional 60-watt incandescent bulb as it would provide the same level of brightness.

These bulbs are available in different colour temperatures to suit different rooms and locations.  A warm white colour (usually between 2700K-3000K) creates a soft and cosy atmosphere that works well in living rooms and bedrooms.  Cool white (4000K) is a brighter and cleaner shade of white.  This makes it suitable for kitchens, bathrooms, and offices. A Daylight colour (6000K or higher) will provide a crisp white light that is the go to choice for workspaces and commercial settings.

E27 GLS bulbs are available in a wide variety of lumens which is how we measure brightness.  This means that one with a lower amount of lumens (such as 470 lumens) can be used for decorative lighting whilst one with a much higher amount of lumens (such as 1500 lumens) can be used for ceiling lights.

Many E27 GLS bulbs are also dimmable which allows its users to adjust the brightness of the bulb as desired.  You should always check that your bulb is compatible with your dimmer switch.  All halogen and incandescent bulbs will be dimmable but cannot be used with a LED compatible dimmer switch.  Some LED bulbs are not dimmable and will require a compatible dimmer switch.  They will advise if they are dimmable on the box or website they have been purchased from and any instructions on compatible dimmer switches should be advised on the accompanying datasheet.

To conclude - an E27 GLS bulb is a standard large screw-cap light bulb which has a traditional light bulb shape which is designed for general lighting.  It has previously been available in incandescent and halogen forms and is now available in LED versions that will give a wide coverage of lighting to cover most average sized rooms.