Case Studies

LED Lighting Brightness Guide

Introduction – Did You Know?...
1/3 of lightbulb sales by Philips and Osram are now LED.
1/3 of UK households have LED lighting installed.
Still, public awareness is very low. Case in point – as part of a display at Wilkinson designed to
inform the public about LED lighting: “Watts are now measured in lumens.” Wrong! …or… the
widespread view that so‐called ‘energy‐saving’ bulbs are the most efficient.
 

Why Switch to LED?
 

1. Energy efficiency (lumens/watt) – 50% savings over fluorescent, 90% over halogen or
incandescent today and improving rapidly. This translates into energy cost savings.
2. Longer bulb life – e.g. halogen 1,500 hours to LED 30,000‐50,000 hours, which also equates to a
lower maintenance cost in commercial/industrial environments.
3. LED bulb costs coming down whilst energy costs are going up.
4. Many LED bulbs are dimmable, unlike fluorescents.
5. Colour temperature – LEDs available in a range of ‘warm’ to ‘cold’ light versions as well as a range
of colours for specialist uses (e.g. night lighting of Millennium Bridge in York).
6. Flexibility– not only available in bulbs but bendable strips and sheets, range of beam angles, fitting
types, frosted vs unfrosted, etc.
7. Excellent for off‐grid installations – because (a) limited power is available and the cost per watt of
energy delivered is high, and (b) LED is widely available in 12V DC.
8. No start‐up delay when switching on, unlike many fluorescents.
9. Works better in cold environments than fluorescents.
10. Less heat output than other technologies – especially important in hot climates, in refrigeration
lighting, and to reduce electrical fire danger.
 

Reason 1: Energy Efficiency
 

There’s no point replacing bulbs to reduce watts, if you’re reducing the light output to below your needs.
So you need to look at lumens (light output) together with watts (power consumption).
Energy efficiency is measured in lumens per watt. That’s how much light output you’re getting for a given
amount of power. It’s important to calculate lumens/watt because even among LED bulbs, there’s quite a
range of efficiencies. Curiously, you won’t find lumens/watt figures on product packaging. So you’ll have to
calculate it yourself. Fortunately, it’s not hard. For example, if you see a 3W bulb emitting 300 lumens,
that’s 100 lumens/watt. You’ll want to strive for 100+ lumens/watt, which is usually possible if you look
around. Prototype Cree LED bulbs have surpassed 300 lumens/watt, so it’s just a matter of time before the
bar is raised once again.
 

Reason 2: Longer Bulb Life
 

This is a massive issue for companies employing facilities management contractors high hourly rates to
change light bulbs – even more so when the bulbs are out of reach and require hiring in a scissor lift. With
halogen GU10 bulbs, which last 1,500 hours, it’s a no‐brainer to replace them with LEDs, which last 25,000+
hours. In such a situation, even when the LED bulbs cost at least twice as much as halogen bulbs, you can
easily develop a ‘business case’ for switching – based on bulb life alone.
For everyone else, bulb life is the second factor to include in cost savings calculations, even if it’s a quick
and rough mental calculation.
 

LED Lighting Brightness Guide

Knowing what's Watt...

Conventional lighting based upon incandescent filament bulbs is traditionally referred to as having an output in Watts. This allows us to have a good understanding of how bright it will be as there is an approximate correlation between power consumed by the bulb (Watts) and brightness.  The problem with LEDs is that they use much, much less power than conventional bulbs for an equivalent light output, so using Watts as a measure of comparing brightness is no longer useful.

How Effective Is Your LED Light?

LED lights instead have their outputs stated in Lumens which is a direct measurement of brightness rather than power consumption. Raw Lumens is a measure of the theoretical maximum brightness of the LED chips themselves, based on the chip output and drive current. However, once these chips are assembled into the lamp complete with the lens and housing there will be losses that reduce the actual light output, so a better measurement is Effective Lumens which takes into account these losses and tells you about the useful visible light that is produced. The Effective Lumens value will always be lower than the Raw Lumens value (sometimes by a huge amount) so care should be taken when comparing LED lights that you are looking at like-for-like outputs.

All of our LED lights have their outputs stated in Effective Lumens (where manufacturer's data is available) and the higher the value, the brighter the light will be.

Quick reference table

You can use this table as a guide to understand how bright an LED light will be compared with a conventional light.