Buying LED lights? What lumens, Kelvin, watts and CRI actually mean
You need a new light bulb. Simple enough, right? Then you look at the box and you see something like...
GU10. 4.7W. 345 lumens. 2700K. CRI 90. 36°. Dimmable.
Suddenly, buying a light bulb doesn't feel quite so simple. Modern LED lighting is more energy efficient and gives us far more choice than older lighting technologies, but it also means there are more numbers and terms to understand. The good news is that most of them are actually quite straightforward. Here's what to look for when you're buying an LED bulb or light fitting – and what those numbers really mean.
Watts vs lumens: what's the difference?
This is probably the most important change to understand when buying LED lighting. For years, we associated watts with brightness. Most people had a reasonable idea of what to expect from an old 40W, 60W or 100W bulb. But watts don't actually measure brightness.
- Watts (W) tell you how much electrical power a light uses.
- Lumens (lm) tell you how much visible light it produces.
That's an important distinction with LEDs because they can produce plenty of light while consuming relatively little electricity. As a rough comparison:
Traditional incandescent bulb |
Approximate light output |
|---|---|
| 40W | 470 lumens |
| 60W | 800 lumens |
| 75W | 1,050 lumens |
| 100W | 1,500 lumens |
So, if you're replacing an old bulb and want roughly the same brightness, compare the lumens rather than trying to match the wattage. And remember: more lumens isn't automatically better. A bedside lamp doesn't need the same output as a bright task light. The right brightness depends on where the light is going and what you're using it for.
What does Kelvin mean on an LED bulb?
Once you've decided how bright you want your light to be, the next number to look at is Kelvin (K). Kelvin describes the colour temperature of white light. The slightly confusing part is that a lower number produces a warmer-looking light, while a higher number produces a cooler-looking light.
- 2700K – warm white
A soft, warm-looking light similar to the traditional glow many people associate with older incandescent bulbs. - 3000K – warm/neutral white
A slightly cleaner, crisper white while still retaining some warmth. - 4000K – neutral/cool white
A cooler, brighter-looking white often associated with more practical or task-focused spaces.
So, which should you buy? There's no single correct answer. Think about how you want the space to feel and what you'll be doing there. A warm 2700K lamp might look fantastic beside a sofa in the evening but wouldn't necessarily be your first choice above a workbench. Likewise, a crisp 4000K light that's useful in a practical workspace may feel too cool for your bedroom.
What is CRI?
Another number you may find on better-quality LEDs is CRI, which stands for Colour Rendering Index. In simple terms, it relates to how faithfully colours appear under a particular light source. Why should you care? Think about food in a kitchen, clothes in a dressing area, artwork on a wall or the carefully chosen paint colour in your new living room. The quality of the light can affect how those colours appear. A higher CRI can be particularly worth considering where accurate and attractive colour appearance is important. It's one of those specifications that people often overlook when buying lighting – but one that can make a noticeable difference to the finished result.
What does beam angle mean?
If you're buying a GU10, spotlight or downlight, you may also see a figure expressed in degrees – for example, 36°. That's the beam angle. It describes how widely the light spreads from the fitting. A narrower beam produces a more concentrated area of light, which can be useful for highlighting artwork, furniture or architectural features. A wider beam distributes the light over a broader area, making it more suitable for general illumination in many situations. This is why two downlights with similar lumen outputs can produce very different results. One might create a tight pool of light while another spreads that light across a much larger area.
GU10, B22 and E27 – what do they mean?
These aren't descriptions of the light itself. They tell you about the lamp base or fitting. Some of the ones you'll commonly encounter in UK homes include:
- GU10 – the twist-and-lock fitting commonly found in spotlights and downlights.
- B22 – the traditional bayonet cap found in many UK lamps and ceiling fittings.
- E27 – a larger screw fitting, sometimes called an Edison screw.
- E14 – a smaller screw fitting often found in decorative lamps and smaller light fittings.
You need the correct base for the fitting you're putting the lamp into, so it's always worth checking before ordering a box of new LEDs. Also bear in mind that many modern light fittings use integrated LEDs. In those fittings, there may not be a conventional replaceable bulb at all.
Can all LED bulbs be dimmed?
No – and this is an easy mistake to make. If you want to dim your lighting, look specifically for an LED that's marked dimmable. But that's only part of the story. The LED lamp or fitting and the dimmer control also need to be compatible. An unsuitable combination can result in flickering, buzzing, a poor dimming range or unstable operation. So if dimming is important to you – particularly if you're installing several downlights or creating a new lighting scheme – it's worth considering the controls at the same time as the lights themselves.
What about smart bulbs?
Smart bulbs add another layer of choice. Depending on the product and system, they can allow you to control lights from an app, change brightness, create schedules and, with some products, adjust the colour or colour temperature. They're useful in the right situation, but don't assume every light in your home needs to be smart. Before buying one, ask yourself what problem you're trying to solve. If you want a lamp to switch on automatically while you're away, a smart bulb might be useful. If you want several lighting circuits throughout a kitchen or extension to work together, a properly planned lighting-control system may be a better approach. Technology should make your lighting easier to use – not more complicated.
So, what should I look for on the box?
Next time you're buying an LED light, you can decode the label in a few seconds. Take this example:
GU10 | 4.7W | 345lm | 2700K | CRI 90 | 36° | Dimmable
It tells you:
- GU10 – which type of fitting it uses
- 4.7W – how much electrical power it consumes
- 345lm – its light output
- 2700K – a warm-white colour temperature
- CRI 90 – information about its colour-rendering performance
- 36° – how widely it distributes its light
- Dimmable – it can be dimmed when used with suitable compatible controls
Once you understand those basics, choosing an LED becomes much less confusing.
The right bulb is only part of good lighting
You can buy an excellent LED and still end up disappointed if it's in the wrong position, illuminating the wrong area or being asked to do a job it wasn't intended for. That's the difference between simply buying a light and planning good lighting. If you're replacing one lamp, understanding the numbers on the box may be all you need. If you're planning a new kitchen, extension, renovation, garden or complete lighting upgrade, it's worth thinking about the whole scheme – including positioning, switching, controls and how the space will actually be used.
Choosing the right LED lighting? Let LAIRD Electrical bring your ideas to life.
Choosing the right LED lighting involves more than simply picking a bulb. Brightness, colour temperature, beam angle and dimming compatibility can all affect how a room looks, feels and functions. At LAIRD Electrical Contractors, we help homeowners across Leeds and Yorkshire create practical, energy-efficient lighting solutions tailored to their homes. Whether you're upgrading existing fittings, installing new downlights or planning a complete lighting scheme, we're here to help.
From modern kitchen lighting and feature lighting to outdoor illumination and smart lighting controls, we can help you achieve the right balance of comfort, functionality and efficiency. With competitive pricing, clear quotations and a 12-month workmanship guarantee, you can have confidence that your lighting installation is in professional hands.
Contact LAIRD Electrical Contractors today to discuss your LED lighting requirements, plan a lighting upgrade or request a competitive quotation.
Call 0113 4180 697 or tell us about your lighting or electrical project.
What are domestic electrics and why is professional electrical work so important?
Electricity is something we rely on every day, often without giving it much thought. From lighting and heating to kitchen appliances, home offices and electric vehicle charging, our homes depend on electrical systems that are safe, reliable and capable of keeping up with modern life. Whether you’re replacing an old consumer unit, installing additional sockets or planning a complete rewire, the quality of the electrical work matters.
Unfortunately, most homeowners have heard stories about tradespeople who fail to turn up, leave jobs unfinished or carry out work that falls short of the expected standard. Experiences like these can make it difficult to know who to trust, particularly when the work involves something as important as your home's electrics. Unlike decorating or other cosmetic improvements, much of an electrical installation is hidden from view, and poor workmanship can have serious consequences. That's why choosing a suitably qualified, experienced and reputable domestic electrician is so important.
At Laird Electrical Contractors Ltd, we believe homeowners should feel confident about who they're inviting into their property. Understanding why professional electrical work matters, what qualifications and credentials to look for, and how to recognise a trustworthy contractor can help you make an informed decision before any work begins.
What are domestic electrics?
Domestic electrics refers to the electrical systems, wiring and equipment installed in residential properties, including houses, flats, extensions and outbuildings. These installations distribute electricity around the home, supplying power to lighting, sockets, appliances, heating controls and other electrical equipment. Domestic electrical work includes everything from minor repairs and alterations to major installations and upgrades.
Some of the most common services include:
- Full and partial house rewiring
- Consumer unit and fuse box replacements
- Additional sockets and switches
- Indoor, outdoor and security lighting
- Electrical fault finding and repairs
- Electrical testing and inspections
- Electrical installations for kitchens, bathrooms and extensions
- Electric vehicle charger installations
- Earthing and protective bonding
- Electrical upgrades and improvements
Although these jobs vary considerably in size and complexity, they all require an appropriate understanding of electrical safety and installation standards.
Why are domestic electricians so important?
Domestic electricians are responsible for installing, maintaining and improving the electrical systems that homes rely on every day. Their work helps ensure electricity is distributed safely and that installations are suitable for the demands placed upon them. While some home improvements can be judged largely by their appearance, electrical work requires specialist knowledge and technical understanding. An installation may appear neat and function correctly at first, but that doesn't necessarily mean it has been completed safely or to the appropriate standard.
A competent domestic electrician understands how different parts of an electrical installation work together, how to identify potential risks and how to select suitable materials and protective equipment. They also understand the importance of inspecting and testing their work rather than simply assuming everything is correct because it switches on. Professional electricians play an important role in protecting homeowners, their families and their properties. Whether the work is a small alteration or part of a larger renovation, the same principles of safety, competence and attention to detail should apply.
Why does choosing a professional electrician matter?
There's a difference between someone who claims they can carry out electrical work and someone who can demonstrate the qualifications, experience and professional standards needed to do it properly. Unfortunately, the wider trades industry sometimes suffers from a poor reputation because of unreliable contractors, unfinished jobs, unclear pricing and substandard workmanship. While there are many excellent tradespeople working across the UK, homeowners are right to be careful about who they employ. Electrical work is an area where cutting corners can be particularly costly. Poor installation methods, unsuitable materials or a lack of appropriate testing may create problems that aren't immediately visible. Correcting those problems later can involve additional expense and disruption.
Choosing an established, competent electrical contractor gives you the opportunity to check their credentials, understand how they work and establish what you can expect before the job begins. A professional electrician should be able to explain their recommendations, provide a clear quotation, carry out the work to the relevant standards and take responsibility for the quality of the finished installation.
What should you look for when hiring a domestic electrician?
Before agreeing to any electrical work, it's worth carrying out a few straightforward checks. A reputable electrician should be happy to answer reasonable questions about their qualifications, experience, insurance and the work they're proposing. Here are some of the most important things to consider.
1. Relevant qualifications and competence
One of the first things to check is whether the electrician has the appropriate training, qualifications and experience for the work you need completing. Electrical qualifications demonstrate relevant technical knowledge, but it's also important to establish that the individual is competent to undertake the particular type of installation involved. Someone experienced in small domestic alterations may not necessarily have the same background as a contractor regularly completing complex electrical projects.
Don't be afraid to ask about qualifications, previous experience and whether the electrician has carried out similar work before. A professional contractor should be comfortable discussing their credentials.
2. A legitimate and established business
Before hiring an electrical contractor, check that you're dealing with a genuine business. Look for a consistent trading name, reliable contact details and a professional online presence. For a limited company, you can check its registration details through Companies House. This helps confirm that the company exists, although registration alone doesn't prove electrical competence or the quality of its work. A legitimate contractor should also be willing to provide business details and explain who will be responsible for carrying out the work.
3. Appropriate insurance
Electrical contractors should have appropriate insurance for the services they provide. Public liability insurance is particularly important because it can provide protection in relation to certain claims involving injury or property damage arising from business activities, subject to the terms of the policy. It's reasonable to ask whether the electrician is insured and request confirmation of their cover. For larger projects, you may also want to check that the policy is suitable for the scale and nature of the work. Insurance doesn't replace competence or good workmanship, but it is an important part of operating professionally.
4. Registration with a recognised competent person scheme
Some electrical contractors are registered with government-authorised competent person schemes, such as NICEIC or NAPIT. For relevant domestic electrical work in England, registration with an appropriate scheme can allow a contractor to self-certify compliance with the Building Regulations, where the scheme covers that work. It's important to understand that scheme registration is not a legal requirement for every electrician or every type of electrical job. However, it can be a useful credential to check, particularly when you're arranging work that requires Building Regulations notification. If a contractor claims to be registered, ask for their registration details and verify them directly with the relevant scheme.
5. Evidence of previous workmanship
A professional electrician should be able to demonstrate the standard of work they carry out. This might include photographs of completed installations, examples of previous projects or information about similar jobs they've undertaken. For larger projects, it's particularly useful to see work that reflects the type of installation you're planning. Photographs alone won't prove that an installation is electrically safe, but they can give you an indication of the contractor's attention to detail, organisation and overall approach. You can also ask how the work will be inspected and tested, and what certification will be provided where applicable.
6. Customer reviews and references
Recommendations from previous customers can be one of the most useful ways to assess a tradesperson. Online reviews may provide insight into reliability, communication, punctuality and the standard of service customers have received. Rather than focusing only on an overall star rating, take time to read what people actually say about their experience. For substantial electrical projects, you can also ask whether the contractor can provide references from previous customers who have agreed to be contacted. A recommendation from someone who has had similar work completed can offer valuable reassurance before you commit.
7. A clear, written quotation
A professional electrical contractor should explain what work is being proposed and provide a quotation that clearly sets out the agreed scope. This helps prevent misunderstandings about what is included, what materials will be supplied and whether any additional costs might arise. Before accepting a quotation, check that you understand:
- What electrical work will be carried out
- Whether materials and labour are included
- Whether inspection, testing and relevant certification are included
- The expected timescale for the project
- How unforeseen work or additional costs will be handled
- The payment terms and any deposit requirements
The cheapest quotation isn't necessarily the best option. It's more important to compare what each contractor is offering and whether the proposed work meets your requirements.
8. Workmanship guarantees and aftercare
Before hiring an electrician, ask what guarantee they provide on their workmanship and how they deal with problems that arise after completion.
For example, you might look for a 12-month workmanship guarantee, although the period and terms will vary between contractors. Some may offer longer guarantees, and manufacturers' warranties on electrical products are usually separate from guarantees covering installation work. Make sure you understand what is covered, how long the guarantee lasts and whether any exclusions apply. Where a guarantee is offered, ask for the details in writing. A guarantee can be a useful sign that a contractor is prepared to stand behind their work, but it should be considered alongside qualifications, insurance, references and other evidence of professionalism.
9. Good communication and reliability
Technical ability is essential, but the way an electrician communicates can tell you a great deal about how professionally they operate. A reliable contractor should respond to enquiries within a reasonable time, explain the proposed work clearly and keep you informed if arrangements need to change. They should also be realistic about availability and timescales rather than making promises they cannot keep. When work is taking place in your home, these details matter. Knowing who is attending, when the work will happen and what disruption to expect makes the experience much more straightforward.
Why workmanship should never be an afterthought
Good electrical workmanship goes beyond completing a job that looks neat. It involves using suitable materials, following appropriate installation methods, making secure connections and carrying out the necessary checks. Many important parts of an electrical installation are concealed once the work is complete. This means homeowners often have to rely on the electrician's competence and professionalism rather than being able to inspect every detail themselves. That's why it's worth choosing a contractor who takes pride in their work and is willing to explain how the installation will be completed.
Professional workmanship should also extend to the way your property is treated. Taking reasonable care to protect working areas, keeping disruption to a minimum and leaving the space tidy are all part of delivering a good service. An electrician who values their reputation should understand that the customer experience matters just as much as the technical work.
Why trust and accountability matter
Inviting a tradesperson into your home requires trust. You're relying on their knowledge, their judgement and their commitment to doing the job properly. That trust should be supported by more than a verbal promise. Qualifications, insurance, verified registrations where relevant, customer references, written quotations and clear guarantees all help homeowners make a more informed decision. No single credential can guarantee that every job will be perfect. However, taking the time to check several of these factors can significantly improve your understanding of who you're hiring. A reputable electrical contractor should welcome sensible questions and be prepared to explain how they work. If someone is unwilling to discuss their qualifications, provide basic business details or clarify what's included in their quotation, it's reasonable to consider other options.
Choosing a domestic electrician in Leeds and West Yorkshire
If you're looking for a domestic electrician in Leeds, it's worth taking the time to find a contractor who offers the right combination of technical competence, reliability and professional workmanship.
At Laird Electrical Contractors Ltd, we understand that homeowners want more than someone who can simply complete an electrical job. They want clear advice, dependable service and confidence that their property is being treated with care. We provide domestic electrical services across Leeds and West Yorkshire, covering electrical installations, repairs, improvements and larger projects. Our approach is centred on understanding each customer's requirements and delivering work with care and attention to detail. Whether you're planning improvements or arranging electrical work as part of a renovation, choosing the right contractor is an important first step.
Need a reliable domestic electrician? Put your home in safe hands with LAIRD Electrical.
Your home's electrical installation plays an essential role in everyday life, and choosing the right electrician is about more than simply getting the job done. At LAIRD Electrical Contractors, we provide professional domestic electrical services for homeowners across Leeds and Yorkshire. Whether you need additional sockets, lighting upgrades, electrical fault finding, a consumer unit replacement or a full or partial rewire, we're here to help.
As an NICEIC Approved Contractor, we understand the importance of quality workmanship, electrical safety and reliable service. With competitive pricing, clear quotations and a 12-month workmanship guarantee, you can have confidence that your electrical work is being handled professionally, with care and attention to detail.
Whether you're planning home improvements, renovating your property or need an experienced electrician for essential repairs, choosing a contractor you can trust makes all the difference.
Contact LAIRD Electrical Contractors today to discuss your domestic electrical requirements, arrange a visit or request a competitive quotation.
Call 0113 4180 697 or tell us about your home electrical project.