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Light Bulb Guide

Pagazzi Lighting Bulb Buying Guide

Not sure where to start when it comes to finding the right bulb for the lighting in your home? If you're wondering what the difference between Halogen and Energy Saving bulbs actually is, or you're confused by Edison Screws, then this is the perfect place for you to pick up some of the basic knowledge you'll need to be confident the next time you need to replace a bulb and buy direct from a lighting store like Pagazzi Lighting!

We're incredibly proud to say that all of our store staff are expertly trained to provide excellent service when it comes to bulbs and lighting, so if you still have questions after reading this guide, or if you'd just like a little peace of mind, don't hesitate to visit us in store or get in touch on 0344 257 1908 where one of our friendly and knowledgeable staff will be more than happy to help.

This short guide gives an outline on the differences between bulb types, as well as a brief look at shapes, fittings, colour and brightness.

We get a lot of questions from our customers about how to choose the right bulb for our products, with common confusions coming up time and again. We hope that this information will help you to be more comfortable and confident then next time you visit us for a new bulb.


We know it can be hard to keep up with fast changing lighting technologies, but there's some simple information about the technological developments and legislation that will give you a good head start. Changes made to EU legislation have meant that the lighting industry have had to adapt and adjust to new rules quickly. These legislative changes have already seen the phasing out of incandescent bulbs, and a move towards the gradual phasing out of halogen bulbs in favour of more energy efficient bulb types.

Incandescent bulbs were the most popular bulbs of the 1930's, making use of a wire filament and an inert gas filled glass bulb. These, as well halogen bulbs, use the electrical current passed through the filament in order to heat it to a point where it glows and omits an incandescent glow. Although popular, these bulbs are not very energy efficient, with Halogen bulbs only saving 30% of the energy used. Modern energy saving bulbs and LED bulbs have become the standard in the industry, with high energy efficiency ratings and much longer lifespans.  

Halogen Bulbs

Halogen bulbs are now in the process of being phased out in the EU and many products are no longer being shipped with these bulbs as part of the package due to the switch toward LED. Smaller Halogen bulbs are generally characterised by their small rod cap which are simply pushed into the light fitting. Their larger counterparts feature prongs which are twisted into position in a similar method to Bayonet bulbs. The most popular bulb codes for the smaller halogens are G4 and G9 with the number referring to the distance in millimetres between the prongs. The most common larger bulb codes is GU10 and is primarily found as spotlights in track lighting or recessed ceiling spotlighting. Halogen bulbs use a filament that is heated with an electrical current in order to provide light. The mixture of a metal filament and the small amount of halogen gas helps to maintain the bulb's lifespan through a chemical reaction.

As well as the cap of the bulb needing to be right, it's also important that you get the right shape for your fitting as well. You don't want to come home with a bulb that technically fits, but that sticks out of the fitting ruining the overall look. Again the shape of the bulb will be clearly marked on the packaging of the fitting, so take a note and you can match it up when shopping for a replacement bulb. Where possible it's always best practice to take the old bulb with you when shopping for a new one, just to be absolutely sure you're picking the right one.

LED (Light Emitting Diode) Bulbs

You’ve probably heard a lot about LED bulbs and how they are better value for money and better for the environment. With new EU legislation coming into effect from September 1st 2018, Halogen bulbs will begin to be phased out of the UK Now really is the best time to make the leap to LED.


In order to create light, we need to use energy.  An unavoidable by-product of creating light is that some of the energy ends up being wasted as heat, which isn’t what we want from a bulb. LED Bulbs are generally much cooler than traditional bulbs, with LED bulbs converting up to 85% of all energy used into light, which means only 15% of the electricity you’re paying for is wasted as heat. In comparison, Halogen bulbs waste 65% of the energy as heat, which is a substantial amount of your electricity bill to wasted energy. Switching to LED is not only better for the environment but easier on the pocket, too. Spending a little more upfront on LED bulbs will lead to savings on your energy bill over the course of the bulbs life, savings which far outweigh the initial difference in price between the bulbs.

Energy Efficiency

LED bulbs are also advancing all the time, meaning that although their wattage (the amount of energy required to power the bulb) may be coming down, their lumens (the brightness of light the bulb produces) is rising all the time. As an example, a 5 Watt LED bulb generates just as much light as a 50-watt halogen bulb. This means that LED consumers are spending less on energy, but getting brighter bulbs as time goes on. Don’t let yourself be put off by LED’s low wattage and worry you might end up sitting in the dark! Remember that wattage is not about how bright the bulb is, it’s only a representation of how much energy the bulb will need to run.

Bulb Caps

It's really important to make sure that you find the correct bulb fitting for your light as it will save you from disappointment and expense if you don't check properly. In the UK there are a couple of primary types of bulb caps for domestic fittings. We'll walk you through them one by one explaining the key information you need to be aware of when selecting your cap. It can be a little bit daunting standing in front of the bulb display trying to work out which one is the right one for you, but if you keep the following information in mind, it will help you to narrow down your search. 

Bayonet Bulbs

Bayonet light bulbs are primarily found on the UK lighting market and are recognisable by a push and pull fitting function, where small rods on the base of the cap slide into corresponding grooves in the fitting and can be twisted into place. The most common product codes for Bayonet Bulbs are BC or B22d, with these caps measuring 22mm in diameter. These bulbs are mains voltage with two separate pins and also come in a smaller size known as SBC or B15d, but these are slightly less common.

It is always best to take a note of the bulb code from any new light fittings you purchase to ensure you have a copy for your reference each time you have to replace the bulb. All bulbs are marked with the relevant cap code.Ot

Edison Screw Bulbs

Named after the lighting pioneer Thomas Edison, this is the most popular type of light bulb used in homes across the UK. With an easy screw-in design, the Edison Screw bulb comes in a variety of sizes, the most common of which are the ES/E27 or SES/E14. Similarly to the Bayonet Bulbs, the numbers in the Edison codes refer to the diameter of the cap. These bulbs can also be found in decorative shapes such as the iconic candle-flame design often used in chandeliers. Many outdoor lighting products will use a ES bulb type with European brands opting for this type of fitting in their products too.

Other Common Bulb Caps

Reserved for the majority of Halogen bulbs that are primarily available in two forms, the G caps feature two small prongs or rods that fit into corresponding holes in the bulb. The smaller bulbs are generally characterised by their small rods which are simply pushed into the light fitting. Their larger counterparts feature prongs which are twisted into position. The most popular bulb codes for the smaller halogens are G4 and G9 with the number referring to the distance between the prongs. The EU have recently passed legislation to phase Halogen bulbs out of the UK to be replaced with LEDs. You might expect to see these bulbs in Kitchen spotlights.

Watts vs Lumens

When we're talking Watts and Lumens, what we're really talking about is power and brightness. Back before the ban of incandescent light bulbs, the brightness of a light was measured in watts, which are actually a measure of how much power it took to illuminate the light bulb. Nowadays energy saving bulbs take much less energy to generate the same amount of light. This means that using lumens as the standard of measurement gives a much better indicator of what you're paying for.

In more simple terms, the light emitted by a bulb used to be referred to in Watts, due to the fact that bulbs that could handle more electrical current often shone brighter. A 60W standard bulb used to omit 720 lumens of brightness. Modern energy savings bulbs will omit almost the same level of lumen brightness but at a fraction of the wattage. 

Wattage is measured in Watts and used to be the standard measurement for bulb brightness, determined by the amount of power required in Watts to light the bulb fully. With modern bulbs making use of a much lower maximum wattage, a new measurement for the brightness of bulbs had to be found. Using the lumen scale, and measuring the brightness 360° around the source of light. Similar to this, with spotlights specifically, the lumen scale is used to provide details of the candela or light intensity from the source in a particular direction.

Kelvin Scale

Bulbs have long been available in a variety of colours, designed specifically to help you create a mood or feeling with your interior design. With many vibrant and exciting colours on offer, there's plenty of options for someone looking to add to their colour scheme with their lighting, but lighting doesn't have to be so blunt with colour. Subtle changes in colour on your bulbs can help to make a room feel warm and welcoming or make it feel cold. We're sure you can remember a time where you've gone to a Halloween house party and all the bulbs have bee replaced with red bulbs to add to the scare factor. Lighting colour can also subtly affect your mood and feeling about a home due to a bulbs rating on the Kelvin Scale. Most bulbs fall somewhere between 2000K (Warm Sunrise) to 8000K (Cool Summer Shade) with our recommendation for the perfect lighting coming in between 3100K and 4500K.

The reason we decided to highlight the Kelvin Scale is to show how a small change in Kelvin rating can have a big impact on the lighting in your home. Choosing a bulb within our recommended range will mean that you have a natural daylight effect in the hours when there's no natural light available. The Kelvin Scale measures the colour temperature of a bulb, and refers to whether a bulb omits a warm or cool light. You'll want to find the happy medium between brightness, warmth and clarity with your bulbs, so picking a bulb within our recommended ranges will give you the best chance at finding the perfect lighting. You'll want to create a cosy and welcoming atmosphere with warm soft ambient lighting rather than aiming for brightness and creating a cold feel to your room.

Colour Rendering Index (CRI)

Each bulb is also given what's known as a CRI value. This stands for Colour Rendering Index and refers to a light bulbs ability to correctly represent colours. You want to ensure that you choose a bulb that accurately shows the colour of the wallpaper you spent hours debating over, rather than have a bulb cast it into a slightly altered shade you didn't pick out! The traditional incandescent light bulbs scored in the high 90s for their CRI value which is considered near perfect meaning that your lettuce will look green and your tomatoes will look red. It is not advised to go below 80 for your CRI score when picking out light bulbs or you may find yourself sitting in a room full of colours that look a little bit off!