Help and Useful Information for Buying Light Bulbs at G&T's Original Warehouse

Gone are the days when there was just one type of light bulb, since traditional incandescent light bulbs were phased out, various types of bulbs are now available, each with their own pros and cons. No longer is buying a bulb by its number of watts ideal, technology has evolved and shopping for light bulbs has changed.

This guide will help you find the right bulb, and explain the different features, types and technologies of the light bulbs we stock. The guide is divided in to four sections; The different bulb cap fittings, bulb shapes, bulb colours and the different bulb technologies now available.

1. Choose the right light fitting:

There is a variety of different light bulb caps or bases. Somewhere on your lamp, light fitting or in its instructions will be the correct bulb fitting that it requires. This section shows most of the popular fittings. Make sure you check this carefully as the wrong bulb cap will not work in your light fitting.

Large Bayonet Cap

Large Bayonet Cap (B22)

The UK's most common cap fitting, with a push and twist action. B22, or BC, is 22mm diameter and with two locating lugs. It is usually found in ceiling pendants.

Small Bayonet Cap

Small Bayonet Cap (B15)

A smaller version of the bayonet cap, with a push and twist action. B15, or SBC, has a 15mm diameter. Used in smaller decorative fittings, chandeliers and appliances.

Large Edison Screw Cap

Large Screw Cap (E27)

Edison Screw (ES) or E27 is the UK's second most common cap fitting, featuring a screw-in connection with a 27mm diameter. Found in a vast range of applications.

Small Edison Screw Cap

Small Screw Cap (E14)

A smaller version of the screw cap, with a screw-in connection. E14, or SES, has a 14mm diameter. Used in smaller decorative fittings, chandeliers and appliances.




GU4 Bulbs have two long pins with a 4mm distance between them. Found on low voltage lamps, they have a push fit action and come in Halogen or LED variants.

GU5.3 (MR16)

GU5.3 (MR16)

GU5.3 (MR16) Spotlight Bulbs have two short pins with a 5.3mm distance between the pins. They have a push fit action and come in Halogen or LED variants.



GU6.35 Spotlight Bulbs have two short pins with a 6.35mm distance between them. GU6.35 bulbs have a push fit action and come in either Halogen or LED variants.



GU10 Spotlight Bulbs have a similar looking fitting to bayonet cap, with two pins on the bottom, 10mm apart. GU10 Spotlight bulbs have a push, twist and lock action.


G4 Capsule

G4 Capsule

G4 Capsule two pin bulbs are commonly used in low voltage decorative light fittings and intricate light displays. They have a 4mm distance between the two pins.

GY6.35 Capsule

GY6.35 Capsule

GY6.35 Capsule two pin bulbs are commonly used in low voltage decorative light fittings and intricate light displays. They have a 6.35mm distance between the pins.

G9 Capsule

G9 Capsule

G9 Capsule bulbs are commonly used in low voltage decorative light fittings and intricate light displays, and have two looped metal prongs on the bottom, 9mm apart.

R7S Tube

R7S Tube

These linear double ended bulbs feature a white connector on each end, and are found in flood lights and security lighting. They usually measure 78mm or 118mm long.

2. Find the best shape:

Now you have your right bulb fitting, you will need to choose the best shape for your lamp or light fitting. Each type of bulb provides a slightly different spread and angle of light, from the narrow beam of a spotlight to the 360 degree spread of a globe or golf ball bulb.
The 'right' shape of the bulb and spread of the light is partly down to your personal preference, but also consider how the bulb will look when it is switched off as well as on, and also if it fits sensibly in your lamp or light. You wouldn't want a large stick shape if it will protrude from the top of your table lamp.

Classic Shaped Bulbs
Candle Bulbs
Spiral and Stick Bulbs
Globes and Golf Ball Bulbs
Reflector Bulbs
Spot Light Bulbs
Capsule Light Bulbs
Appliance Pygmy Bulbs

3. Choose the best bulb technology:

That old incandescent light bulb you're looking to replace has been phased out, and soon will no longer be available at all. There are now three different types of bulb technology, and here we will explain the differences between them.

LED Light Bulbs

LED (Light Emitting Diode)

Annual running cost: £26.28

  • Ultra low running costs (90% energy saving compared to old incandescent bulbs, which will save you money)
  • Last up to 30x 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

The future of light technology, and the one we recommend as your first choice. Don't be put off by the upfront cost of LED light bulbs, they could save you hundreds in the long run. The most energy efficient bulb, LEDs use up to 90% less energy than a traditional incandescent, and can last up to 25 years. An LED bulb could save you more than £180 over its lifetime, and with instant full light as soon as you flick the switch, is the smart choice.

Compact Fluorescent Lamp Light Bulbs

CFL (Compact Fluorescent Lamp)

Annual running cost: £35.04

  • Low running costs (80% energy saving over old incandescent equivalent)
  • 10x longer lifetime than incandescent bulbs (approximately 10,000 hours)
  • Can take up to two minutes to reach 100% brightness
  • Require careful disposal
  • Non-dimmable
  • Bulbs tend to be larger than the incandescent bulbs so may not be suitable for all light fittings

CFLs are cheap and widely available in most sizes and outputs. Older CFLs were slow to brighten, but this has improved considerably in recent years. CFLs use up to 80% less energy than incandescent bulbs and quickly pay for themselves in energy savings, but not everyone likes the light they emit. They have an average lifespan of 10 years.

Halogen Light Bulbs


Annual running cost: £105.12

  • Value option of the current technologies
  • Inefficient running costs (only 20% energy saving versus incandescent)
  • Short lifetime (approximately 2,000 hours)
  • Full brightness instantly
  • No harmful chemicals so they are safe for the environment
  • Dimmable
  • Get hot when used after a period of time

Similar to incandescent light bulbs in colour and quality as it uses a tungsten filament, halogen bulbs also use the same amount of energy, making them significantly more expensive to run than other energy savers. With an average lifespan of just 2 years, a halogen bulb also emits a lot of heat, meaning it is unlikely to pay for itself before it fails.

4. Find the right brightness and colour:


With classic incandescent bulbs, brightness was measured in watts - which is actually a measure of power. Since the introduction of energy-saving bulbs, light output is measured in lumens. The higher the number of lumens, the brighter the light. As a rough guide, 400 lumens is suitable for a bedside lamp, and 1,5000-3,000 lumens in total is ideal for an average sized living room. Use the chart below to see equivalent watt and lumen output for the different types of bulbs available today.

Lumen and Watt Conversion Chart

Colour Temperature

Almost all bulbs give off a white glow, however this can vary from a cosy 'warm white' to a cold 'cool/bright white'. Today's light bulbs are all about warmth, with every bulb having a colour temperature rating. This is measured in degrees of kelvin and denoted by a numerical figure followed by the letter 'k' on a scale from 1,000 to 10,000, with 1,000 being the warmest, and 10,000 the coolest. Traditional incandescent bulbs have a colour temperature of 2,700K, with a slightly yellowish glow.
Here are some examples detailing which colour temperatures may work better in different room types:
Extra Warm White 2,700K - This classic yellowy orange temperature is ideal for lounges, living rooms and bedrooms. This style of light is warm and cosy with an inviting, intimate relaxed feel.
White 3,000K - Best used in kitchens, bathrooms and conservatories. Slightly whiter than warm white, allowing you to see better, but not too cold.
Cool White 4,000K - Suitable for kitchens again, cool white contains more blue light, making it better suited for cupboards, garages, offices and retail premises.
Daylight 6,500K - This bluish white light resembles natural daylight at noon, great for reading, projects, accent lighting and various other tasks. Generally found in commercial applications.
Please refer to the guide below for the Kelvin colour temperature chart and real-world examples.

Lightbulb Kelvin Chart

Last updated December 2019 with updated prices and info.

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