Light bulb buying guide

Light bulb buying guide

Holly, self-taught DIYer, Cardiff

Guide written by:

Holly, self-taught DIYer, Cardiff

Incandescent light bulbs with screw or bayonet caps are fast disappearing in favour of more cost-effective and efficient bulbs, such as LEDs, CFL bulbs, halogen, and tube lights. From GU base bulbs to candelas, lumens and Kelvin, read on to pick the right bulbs for your home.

Important features

  • Base
  • Energy consumption
  • Number of hours
  • Colour temperature
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Essential criteria for choosing a light bulb

Les culots et les formes des ampoules LED connectées

In the past, choosing the right light bulb was a question of knowing whether you needed a screw or bayonet cap, and the wattage. Nowadays, to pick a suitable bulb you'll need to determine:

  • the base - from a choice of around 20 types;

  • incandescent bulbs - inexpensive but energy-intensive, instant full brightness (suitable for any room);

  • halogen bulbs - 30% less energy consumption, instant full brightness (suitable for passageways, outdoors), 2-year lifespan;

  • CFL or energy-saving bulbs - inexpensive, gradual brightness (suitable for living rooms), 6 to12-year lifespan;

  • LED - the most cost-effective, instant full brightness, avg. 15-year lifespan (suitable for both indoors and outdoors). Blue light is harmful for the eyes (of children in particular). Choose a dimmable LED bulb for lights with a dimmer switch.

  • type of light bulb:

  • brightness in watts (W): the higher the wattage, the more electricity the bulb consumes;

  • 1055 lm for a 75 W bulb

  • 806 lm for a 60 W bulb;

  • 470 lm for a 40 W bulb;

  • 249 lm for a 25 W;

  • brightness in lumens (lm): the higher the lumens, the brighter the bulb. The equivalent in an incandescent light bulb is:

  • light intensity in candelas (cd) - the higher the value, the more intense the light emitted from the bulb (1cd = the intensity of a candle, 1 cd = 1 W of an incandescent light bulb);

  • light rendering with the Colour Rendering Index (CRI), 80 for functional purposes, 100 for white light (daylight).

  • colour temperature in degrees Kelvin (°K) - the higher the value, the colder the colour will be (6500°K is equivalent to daylight, 4000°K for a soft light, 2700°K for a warm light).

  • energy consumption - from A+++ (energy-saving) to G (energy-intensive);

  • the number of operating hours or years (from 2 to 25 years);

  • number of times the light is switched on and off (choose a higher value for hallways and bathrooms);

Types of light bulb base

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LED bulb

The 5 different types of light bulb and what they're used for

Light bulbs can be divided into 4 broad categories. Roughly speaking, at the same wattage, these differ in energy consumption and lifespan. The difference lies in how they are used. Let's shine a spotlight on light bulbs!

1. Incandescent light bulbs


Although it used to be the most common, the incandescent light bulb is energy intensive, resulting in it barely being used anymore. However, some decorative light bulbs are still available.

2. Halogen light bulbs


Halogen bulbs are a good alternative to incandescent ones thanks to their similar shape, the quality of light they provide and their lower energy consumption. The bright light that these emit makes them suitable for use with detailed work, in passageways and also for outdoor purposes, as they are resistant to cold.

With the energy-saving version, you can cut your energy consumption by 20 to 30% compared to a conventional halogen bulb. It has an operating life of between 1,000 to 5,000 hours. Another strong point: immediate lighting.

3. CFL light bulbs


CFL light bulbs are also known as energy-saving light bulbs. They reduce your electricity bills with a consumption rate four times lower than incandescent bulbs, which works out at a saving of 80% over a lifespan of 6,000 to 12,000 hours. Because they don't light up quickly (they take under a minute to warm up), they are not suited to being switched on and off repeatedly. These are more appropriate for living areas (living rooms and kitchens). Quickstart technology has reduced the warm-up time (+60% in 30 seconds).

The pros: a wide range of shapes, colours, sizes and the option of using a dimmer on some versions. Cons: potentially toxic when used at a distance of less than 30 cm.

4. LED light bulb


When it comes to energy consumption, LED bulbs are the most cost-effective, and also last 5 times longer than a CFL bulb (their lifespan can reach 30,000 hours). Because they light up instantly and are impervious to frequent use and cold temperatures, they are suitable for both indoors (where long-lasting lights are required) and outdoors. Although they represent huge technological progress, the pros and cons of LED light bulbs as well as their incompatibility with dimmer switches - one of the downsides - means they cannot replace every light bulb in the house. Blue is harmful to the eyes (especially for children) so opt for white.

5. Specialist light bulbs

The 5 different types of light bulb and what they're used for

There are many specialist light bulbs available for special circumstances such as lights for your kitchen appliances (e.g. ovens and fridges) and small devices (e.g. torches and night lights).

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Specialist light bulbs

Calculating wattage to determine the brightness of the bulb


Nowadays, watts (W) are not the only indication of brightness on a light bulb: lumens also comes into play! When we're speaking about a light bulb's power, we mean watts. The brighter it is, the less cost-effective it will be. In any case, its wattage must match that of the light fixture, otherwise it might burn out. And when we want to know the amount of light emitted (luminous flux), we're talking about lumens. Bulbs with higher lumens are brighter (they emit a light that's closer to natural light). This means that you can find the same luminous flux in bulbs of different wattage (W).

Watts to lumens conversion

Do you need to change an old bulb and convert watts to lumens? Use the following values:

  • 1055 lm for a 75 W bulb

  • 806 lm for a 60 W bulb;

  • 470 lm for a 40 W bulb;

  • 249 lm for a 25 W bulb.

Using this flux, you can calculate the light emitted by your bulb (the lm/W ratio), i.e. its ability to convert electrical energy (W) into light energy (lm).

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Light bulbs

What is a candela? The base unit of luminous intensity


To quantify the output of light in any given direction, we talk of luminous intensity or luminous flux. The unit is known as the candela (cd).

This intensity greatly depends on the angle of your light bulb beam: a wider angle results in a less intense beam of light. One candela is equivalent to 1 W for an incandescent light bulb; a candle gives off around 1 cd.

Technical specifications: CRI, colour temperature and energy class

Besides the already mentioned values (W, lm, cd), light bulb packaging also provides other information that can help you make the right choice.

Colour temperature

Colour temperature

Light comes in a range of colours and these are expressed in Kelvin. Basically, the higher this temperature is, the colder the light.

  • The brightness of a cold white or blue light will be rated higher than 6000°K, which is what you normally use in your kitchen, bathroom or office.

  • A neutral white will be between 4000 to 4500 K, which is ideal for a living room where you need a less aggressive light.

  • A warm yellow/orange light will be rated at under 3000°K.

Colour Rendering Index (CRI)

On a scale of 1 to 100 (close to white light or daylight), this can be used to evaluate a light bulb's capacity to transmit neutral colours. A CRI of 100 is a white light, a CRI of 80 is more than enough for functional purposes.

Energy consumption

Bulbs are classed from A+++ (energy-saving) to G (energy-intensive). Class A+++ is preferable.

Lighting cycle

This is the number of times a bulb can be switched on and off before it burns out. For toilets and hallways, choose light bulbs with extended lighting cycles.

Warm-up time

Warm-up time tells you how long it takes the bulb to reach its maximum brightness (when switched on). For stairs, toilets or entrances, it's best to opt for a bulb with a fast warm-up time.

Types of LED light bulb base

LEDs come in many shapes and are available with a wide range of base styles (other styles are only available for certain bases). So you can easily switch from conventional light bulbs to an energy-saving version without a headache!

B22 LED light bulb

Types of LED light bulb base

B22 LED light bulbs: these bayonet bulbs only work with the classic B22 base fitting.

E14 LED light bulbs

Types of LED light bulb base

E14 LED light bulbs: Their slim design and 14 mm screw base fit conventional low-wattage lamps (3 to 7 W), giving you a luminous flux of between 150 and 500 lm. Ideal for replacing the old bulbs from your decorative lighting (bedside lamps, bathroom cabinet, etc).

E27 LED light bulbs

: equipped with a 27 mm screw cap, this light bulb suits all light fixtures. Since these emit a strong light, they're idea for interior design creations.

E40 LED light bulbs

Types of LED light bulb base

E40 LED light bulb: an innovative bulb designed for outdoors (often for public lighting) and which adapts to existing fixtures.

G4 LED light bulbs

: these have visible 4 mm pins. They're designed for low-energy illumination (12 or 24 V) in small light fixtures in the kitchen, bathroom and even campervans (they can be recessed).

G24 LED light bulbs

: with the rotating base of this ceiling light, you can easily angle the light exactly where you want it.

G9 LED light bulbs

: despite their small size in the shape of a capsule, they run on 220 V. These are also suitable for use in your chandeliers and various lamps.

GU5.3 LED light bulbs

: these are low-voltage bulbs (12 V) that are designed for use in damp locations. But ever-flexible, they're also popular for use as spotlights, offering a 30° to 120° angle.

GU10 LED light bulbs

: suitable for targeted or extended lighting such as lamps or spotlights.

GX5.3 LED light bulbs

: recessed, these take up very little space (in cabinets, cupboards, etc.) and are ideal for illuminating even in small spaces with a 220 V power supply.

MR16 LED light bulbs

: these bulbs can easily replace your MR16 halogen bulbs, which use more energy than LEDs. Their compact size means they can be fitted into even the most discreet fixtures without impacting the range of its light beam, which is adjustable thanks to the bulb's flexibility (just like the GU5.3 bulb).

R7S LED light bulb

: with their pencil shape, these bulbs emit a powerful luminous flux (up to 44,000 lm depending on the model) designed to illuminate large spaces. If you want to adjust the brightness of your bulbs, opt for dimmable light bulbs (which let you adjust the intensity of the light).

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R7S LED light bulbs

4 main types of light bulb base


The most common light bulb bases are generally:

  • B22, a.k.a bayonet

  • E14, a.k.a. small screw base

  • E27, large screw base

  • GU10 - the majority of spotlights

Other bulbs you might need to replace are the ones in your fridge and oven. While light bulbs designed for the oven can be used in a fridge, the opposite doesn't hold true due to the high temperatures a cooker reaches. In any case, there's no need to panic, because the bases are standard (E14), it's only the glass part that is made smaller to fit the fixture.

What is a downlight?


These are a lights that are recessed into the ceiling. If you're looking for decent light intensity over a wide radius, this is what you need. Downlights normally come with a swivel head (widely used in trade).

As for the light bulbs, while energy-saving ones are the most common, there's nothing to stop you from choosing a model suitable for halogen or LED bulbs.

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The advantages of LED tube lights

The main types of LED tube light and bases


Simply put, LED tube lights are similar to fluorescent tube lights except that they're much cheaper to run thanks to LED technology. If you're going to replace an old fluorescent tube with an LED tube, the same factors should be taken into consideration as with light bulbs. The most popular tube lights:

  • 26 mm diameter T8 LED tube light;

  • 30 mm diameter T110 LED tube light;

Fluorescent light starters


If your fluorescent light is flickering, try changing the starter. This is a small cylindrical electrical device that comes in different styles, so make sure to look at the letter and digit before replacing it (these are written on top, just replace it with an identical one).

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Tube lights

Final tips for choosing the right light bulb

Final tips to choose the right light bulb

  • Pay attention to the size of the bulb and type of base! If they don't match your fitting, you won't be able to install your light bulb.

  • The warm-up time shouldn't be overlooked: there's nothing more annoying than a hallway light that takes forever to light up!

  • Remember to switch off the electricity before changing the bulb!

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Guide written by:

Holly, self-taught DIYer, Cardiff

Holly, self-taught DIYer, Cardiff

First of all, my studies have nothing to do with decoration or DIY as I was specialised in management. My passion in DIY started 5 years ago (very recently!) Everything started when we bought a house to renovate from floor to ceiling. As I’m a self-taught person, I started working on different house projects both inside and outside. My husband helped me but the student soon overtook the teacher! And as there are a lot of green spaces in Wales, gardening tools have no secrets for me. My friends and family often come to me for advice when it comes to DIY. Today, I want to share this knowledge with you!

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