LED Lighting Guide

What You Need

Whether you’re Average Joe or Plain Jane, here’s our LED guide to help make sure you understand what makes the difference between a cheap product and a quality product.

Lumen Efficacy

In simple terms luminous efficacy is a measure of how well a light source produces visible light (luminous flux) from electricity:

i.e. the ratio of lumens to watts

LED lighting has some of the best ratios available when comparing traditional light sources. It is therefore important you purchase reputable products providing at least 80 lm/W, with ever more products providing 100 lm/W as standard.

Some LED products are now providing upwards of 110 lm/W to 150 lm/W, with future products being as efficient as 200 lm/W.

So remember, a higher efficacy results in improved energy savings!


LED products provide vastly improved lifespans compared to traditional lighting, typically being:

Tungsten Bulb  =  4,000 hours

Halogen  =  2,000–4,000 hours

Metal Halide  =  6,000–12,000 hours

Fluorescent  =  6,000–20,000 hours

LED  =  30,000–100,000 hours

So for an LED product with a 50,000 hour lifetime being used in a 9-5 / 5 days per week environment, the product would be expected to last 24.7 years.

Useful Lifetime

Reputable brands label their LED products with a useful lifetime value.

Known as the ‘L’ value it should be provided on all product data sheets, for example:

Lamp Lifetime:  50000h L90

  • This means that after 50,000 hours the product’s luminous flux will be 90% or more of the initial luminous flux (L90) 
  • Generally a product will be rated to L70, unless otherwise stated to L80 or L90.

NOTE:  Do not assume that a product rated with an ‘average lifetime of 50,000 hours’ will be useful for 50,000 hours… The product ‘could’ still work after 50,000 hours but not necessarily provide a minimum 70% of the product’s initial luminous flux.

Check out the simple chart from iGuzzini to show why their products are regarded so highly:


It’s also important to know the ‘B’ value. This is the percentage of the population of LEDs that will not meet the minimum flux value, e.g.:

Lamp Lifetime:  50000h L90 B10

B10 = 10% of the population will achieve less than the L90 flux value after 50,000 hours

Longer lifespans result in maintenance savings and therefore further reduce costs!

What’s colour temperature?

For the kind of mood or atmosphere you’d like to create for your space it’s all about the colour temperature of the lamp… the higher the colour temperature the cooler the impression of the white light.

Click on the chart to see how different light temperatures can be compared in our world and how lamps are classed into temperature Kelvin (K).



The Colour Rendering Index (CRI) is defined as:

“Effect of an illuminant on the colour appearance of objects by conscious or subconscious comparison with their colour appearance under a reference illuminant.”1

CRI is therefore a quantitative measure of the ability of a light source to reveal the colours of various objects faithfully in comparison with an ideal or natural light source, so making reds appear red and not pink.

Look at the colour differences of low and high CRI values as shown by iGuzzini in the images below:

iGuzzini LED Colour Rendering Index - cheap LEDs
iGuzzini LED Colour Rendering Index - high quality LEDs

In general light sources can be provided according to the required CRI value, such as:

CRI >95 for Exhibitions / Museums / Photography

CRI >90 for Food & Fashion

CRI >80 for Architecture & Offices

CRI >70 for Parking & Street Lighting

The CRI value should always be shown on the product data sheet so ensure you have the minimum value you require!

What is UGR

As we know excessive glare can cause eyestrain and contribute to headaches, it is important to reduce direct glare and reflected glare within an office environment.

Therefore we need to take into account reflections from interior surfaces and from the lights themselves. The Unified Glare Rating (UGR) is used as a measure of glare from all visible lamps divided by the the background lumination of the room.

The European Standard EN 12464 regulates the lighting of indoor workplaces, with values of UGR ranging from 5 to 40 with the lower number being better:

UGR < 13 – the glare is discreet and will go unnoticed

UGR > 28 – will certainly cause a distraction

Generally the UGR values are defined in steps of 13, 16, 19, 22, 25 and 28. The UGR limits of lighting products for various environments that should not be exceeded are:

UGR ≤ 16  Technical drawing

UGR ≤ 19  Reading, writing, training, meetings, computer-based work

UGR ≤ 22  Craft and light industries

UGR ≤ 25  Heavy industry

UGR ≤ 28  Railway platforms, foyers

Appropriate luminaire positioning and high quality optics can all help to reduce glare, so before purchasing a product it is advised to choose one that has an appropriate UGR level listed in the product data sheet.

This listed UGR value from the manufacturer is generally in regards to a typical reference situation: room dimensions of 4H / 8H with levels of reflectance of 20% for the floor, 50% for the walls and 70% for the ceiling.

In many luminaire data sheets this listed UGR value should not be taken as a property of the product itself, unless further details are provided by the manufacturer, as in real life installations this value could be lower or even higher. The value taken from the data sheet should only be used as guidance and for comparison of quality between other units.

For installations where achieving a low UGR is critical, it is always highly advised that a full lighting design should be carried out to determine glare values of all luminaires within that room.

How to retrofit and re-lamp with LEDs?


Simple and effective, minimising capital outlay by replacing conventional lamps as they blow, although more expensive in the long term as associated cost savings from ownership and volume purchase discounts cannot be taken advantage of.


Capital constraints may mean that lamps are replaced in phases, therefore replacing them on the basis of the hours they’re switched on for and the savings in wattage. Adopting a room-by-room basis can be used.

Full retrofit

Yielding the greater financial, environmental and functional returns but with the largest capital outlay.

It is important to know that for businesses in England and Scotland Energy Efficiency Financing is available, whilst for businesses in Wales and Northern Ireland interest free energy efficient loans are available, with both options provided by the Carbon Trust.

And don’t forget the opportunity of tax relief through Enhanced Capital Allowances.

For schools, local authorities and parish councils, the NHS and other public sector organisations, 0% finance to purchase and install LED lighting is available through the government supported Salix scheme. Click here for more information.

Which lamp do I need?

Lamp Fittings


Frosted-LED-TubeThe old fashioned form of lighting large spaces such as offices, classrooms and factories.

There are three types that are commonly used with all now being replaced with a direct LED:

  • T12 – the big fat dinosaur tube!  These are the original type of strip light, very inefficient and poor quality light which can be replaced with a T8 LED tube.
  • T8 – the thinner strip light (26mm diameter) that has taken over from the T12 because of improved efficiency.
  • T5 – the newest form of fluorescent lighting and the thinnest (16mm diameter).  Paybacks are a little longer for LED so best to install as lamps fail and need replacing.

LED tube lights can be provided in 2ft, 4ft, 5ft, 6ft and 8ft lengths, with the option of ‘rotating ends’ to improve light direction and dispersal.

N.B.  When changing your old fluorescents for LEDs the switchgear in the fitting needs to be bypassed, so it’s advised to get a qualified electrician to install them for you. Also florescent strip lights need to be disposed of responsibly because they contain mercury, another issue that LEDs don’t have!

Bayonet Sockets

Bayonet-CapsFound in GLS, Filament, Candle & Golf Ball lamps.

These are the most popular, found in all types of settings. There’s two types, the fat one and thin one!

  • B22 – the common ‘fat’ one, found generally in table lamps and ceiling pendants (base diameter 22mm)
  • B15 – the ‘thin’ one usually found on chandelier type fittings and wall lights (base diameter 15mm)
Screw Sockets

Screw-CapsFound in GLS, Filament, Candle, Golf Ball and PAR lamps

Becoming more popular, especially if you’ve been to a large yellow and blue department store, again being fat and thin:

  • E14 / SES –  the ‘thin screw’, SES stands for Small Edison Screw, which is the same as an E14 socket, usually found on chandelier type fittings and small table lamps (base diameter of 14mm).
  • E27 – the ‘fat screw’, Medium Edison Screw, usually found in table lamps, GLS pendants or PAR fixtures (base diameter of 27mm).
  • E40 – the big fat screw cap for more industrialised lamps

Spot-CapsGU10 & MR16

Being the new trend whereby you’ll have a number of insets to your ceiling, or have a number of lights on an ornate piece of metal/wire.

The most common are listed below:

  • GU10 – medium voltage lamps, they’ve got two fat pins so you push and twist the lamp into the fitting to lock it in.
  • MR16 – low voltage lamps that run on 12V and are usually connected by a transformer/driver, which have two thin pins so you just push the lamp into the socket… See below for further information on changing over to LED MR16 lamps.
Changing over to LED MR16 lamps

Changing over to MR16 LED lamps can be a little tricky due to the way they work on a lower voltage, but fear not, we have a couple of solutions for you…

For a direct change and to keep the current wiring set-up, it is important to determine the existing type of transformer in the circuit (most likely situated up in the roof space above the light fittings).

Some circuits have one transformer, but sometimes every individual light fitting has its own transformer.  The transformers tend to come in two varieties – an older wire wound magnetic transformer and a newer electronic low voltage transformer, both of which work by stepping down the mains voltage (240V) to 12 volts allowing the bulbs to function.

SO… The older magnetic transformers will work perfectly with any LED MR16 lamp, allowing you to order what you like.

BUT… there is an issue with the electronic low voltage transformers.  The reason for this is that they need a minimum voltage to pass through them to operate properly.

Not having the right driver (electronics) solution in LED lamps could result in compatibility issues with the existing installed base of transformers once these LED lamps are installed, such as:

  • Lamp not starting up
  • Flicker in the light beam
  • Transformer overheating or saturation, which can lead to shortened transformer lifetime
  • Transformer replacement

THEREFORE… if you have a modern electronic low voltage transformer and want to keep your existing set-up, we recommend purchasing Philips MR16 LEDs.  Philips have been clever and installed a electronic driver within the base of the lamp, enabling broad compatibility with existing electronic and electromagnetic halogen transformers, therefore their low voltage (12V) LED lamps can universally replace 12V halogen spot lamps, mitigating any of the issues described above.

OR… your final option is that you change over to GU10 LEDs, so removing the transformer issue altogether.  You can purchase GU10 fittings that can be wired into the circuit once the transformer/transformers have been removed, therefore using mains voltage electricity.

Confused?  Here’s an example of how MR16 lamps work and why there’s a potential issue:

  • The transformer in a bathroom is 40W – 400W and there are 6 x 50W halogen bulbs in the circuit – giving a total load of 300W.
  • Replacing those 50W halogen bulbs with 5W LED equivalents will put the load through the transformer of just 30W in total.
  • Therefore this means the transformer won’t work correctly, probably resulting in the LEDs flickering.
  • In this instance you are going to need to replace the existing transformer in the circuit – you need to get an LED Driver/Transformer that is matched to operate on the total number of watts in your circuit.

If you’re unsure then our engineer will make sure you make the right decision!

What about beam angle?

As LED Lamps are comprised of single or multiple light emitting diodes on a chip, light is dispersed in a way that mimics conventional incandescent or halogen light sources using complex lenses.

The selection of beam angle depends on application and ceiling height. Beam angles range from 15-60 degrees, but options are dependant upon the lamp model.

LED downlights come with a variety of beam angle options to mimic the light dispersion of traditional halogen reflectors.

  • Narrow beams are best used for accent (spot), product, or display lighting and where ceilings are high so the beam has more room to disperse.
  • Wider-angle beams tend to be used for general distributed room lighting and where ceilings are low so the beam has less room to disperse.

Living spaces generally benefit from beam angles of 36 degrees and upwards.

Dimmable or Non-dimmable?

Don’t forget that not all LED lamps are dimmable, so if you need dimmable lamps then check the product is right.

Likewise if you don’t need dimmable lamps make sure you’re not paying that little bit extra when you don’t have to.

It is also important to know that some dimmers may not operate due to the reduced load from LED lamps.  You will therefore require a compatible dimmer switch to be installed.

Happy shopping, and if you need more information then please feel free to pick up the phone and talk to us… And remember lamps light, bulbs grow!

Call us on 01793 617376

or send us a message