Light bulb buying guide
Introduction
It may be a while since you last had to buy light bulbs. You might be used to finding bulbs by watts, however technology has evolved and this means shopping for bulbs has changed.
We're here to guide you into the new world of light bulbs and will take you through cap fittings, shapes, brightness and designs, step-by-step, so you can find the right bulb for your needs.
Cap fitting
Fitting: What cap fitting do you need?
The first consideration when buying a light bulb is making sure that it will fit the light fitting correctly. To help you find the light bulb you need, they're grouped by cap fitting.
A cap fitting feeds an electrical connection to your light fitting and ensures that it's held in the correct position.
Common cap fittings explained
| Icon | Name | Code | Diameter | Description |
|---|---|---|---|---|
 | Bayonet cap | B22 | 22mm | The UK's most common cap fitting with a push, twist and lock action. Commonly written as BC. |  | Small Bayonet cap | B15 | 15mm | Smaller version of B22 with a push, twist and lock action. Also known as SBC. |  | Edison screw cap | E27 | 27mm | Another regularly used cap fitting with a screw in action. Commonly written as ES. |  | Small Edison screw cap | E14 | 14mm | Smaller version of E27 with a screw in action. Also known as SES. |  | GU10 bulbs | GU10 | 10mm (between pins) | Not dissimilar from a bayonet cap, these types of bulb have a push, twist and lock action. Used in spot lighting. |
How to find the right cap fitting
If you’re replacing a bulb that has come to the end of its life, check the old bulb carefully for a name. If it doesn’t have one, have a look at the base and match it with our cap fitting table below:
If you need to buy a bulb for a new fitting, check the lighting packaging information for details of compatible bulbs and match it with our cap fitting table.
Shape
Shape: What shape do you need?
There are eight common light bulb shapes that you’re likely to find in your home. Although each of these shapes have names (as shown in the tables below), it is important to note that there is no universal set of names used to describe each bulb shape.
Common shapes explained
| Icon | Shape | Description |
|---|---|---|
 | GLS | The most common shape you will find in your home. A traditional light bulb shape that is suitable for a variety of fittings and hasn’t changed since the first model in 1879. |  | Candle | Most commonly used as decorative light bulbs on chandeliers because they are more attractive than the rest, they are also good for smaller spaces such as shallow wall light fittings. |  | Reflector | These are coated with a reflecting material that softly directs light with little shadow. Commonly used in spotlights, recessed lighting or floodlights. |  | Spiral | Designed as a replacement to your old GLS incandescent bulb, these are an energy efficient alternative. |
If you’re not sure which shape bulb you need, take a look at your old used light bulb and match it with a shape in the table below:
Brightness
Brightness: What brightness do you need?
Light bulb brightness is measured by lumens (lm). This information can be found on each light bulb product page, as well as the product packaging.
What are lumens?
Lumens are a measure of brightness. The higher the number of lumens the brighter the light.
Previously we used wattage (w) when measuring brightness, however now you need to look for lumens. The table below shows the comparison between wattage and lumens:
Our light bulbs range between a very dim 100lm to an extremely bright 8550lm. Although most of our range are available in lumens between 200 and 400lm.
Deciding on the lumens you need depends on the brightness you want to achieve in your room, as well as how many combined light bulbs you have in each room.
Design
How do they work? Light bulb technologies explained
There are three different types of light bulb technology (incandescent is no longer available). At B&Q we recommend LED bulbs as your first choice, as they are by far the most cost-effective option over long periods of time.
LED Bulbs
LED (Light Emitting Diode) is very much the future of light technology. It's existed in many forms for a long time (for example in appliances such as TVs, telephones and calculators) but has now truly cemented it's place as the number one technology for home lighting.
▪ Ultra low running costs (90% energy saving compared to old incandescent bulbs, which will save you money)
▪ Last up to 30 x longer than incandescent bulbs (up to 30,000 hours)
▪ Full brightness instantly so you don’t have to wait for it to illuminate fully
▪ No harmful materials – easy to dispose of and safe for the environment
▪ Dimmable options available
CFL Bulbs
Also known as Compact Fluorescent Lamps, these are often referred to as 'energy saving' bulbs.
▪ Low running costs (80% energy saving over old incandescent equivalent)
▪ 10 x longer lifetime than incandescent bulbs (approximately 10,000 hours)
▪ Can take up to two minutes to reach 100% brightness
▪ Non-dimmable
▪ Require careful disposal
▪ Bulbs tend to be larger than the incandescent bulbs so may not be suitable for all light fittings
Halogen Bulbs
This technology was developed from spotlight bulbs and car headlamps, using a gas to produce a brighter light from less electricity.
▪ Value option of the current technologies
▪ Dimmable
▪ Full brightness instantly
▪ No harmful chemicals so they are safe for the environment
▪ Inefficient running costs (only 20% energy saving versus incandescent)
▪ Short lifetime (approximately 2,000 hours)
▪ Gets hot when used after a period of time
Style of light: Do you need dimmable or non-dimmable bulbs?
Dimming your lights changes the visual appearance and mood of your space, and can also save you energy.
A room with dimmable lighting can be great if you have multiple uses for that space. For instance, in a kitchen-diner you may want brighter task lighting when cooking, and then when you’re ready to sit down for your meal, you can dim the lights for a more relaxing atmosphere.
However, not all light bulbs are compatible with a dimmer switch.
1 LED lighting is available in dimmable and non-dimmable versions and can be used either with or without a dimmer switch.
2 Compact fluorescent lights (CFL) are generally non-dimmable.
3 Halogen bulbs can be used on both dimmable and non-dimmable light switches.
What is colour temperature?
Bulbs can offer varied colour temperatures, which are measured Kelvins (K).
▪ The colour temperature of light allows you to create different moods.
▪ Bulbs with low Kelvin value give a warm, yellow light for a cosy atmosphere.
▪ Bulbs with higher Kelvin value produce cool, blue light which is more energising.
The table below shows the difference in Kelvin values:
