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LED Lighting: Lumens and Kelvins

The massive increase in energy costs makes the savings available by adopting LED lighting more compelling.

Each 800 lumen (60W) incandescent bulb running 1.37 hours a day (500 hours) costs £15.60 a year.

An equivalent 800 lumen (9W) LED bulb would cost £2.34 to run for the same period. 

Saving £13.26 ...per bulb ...per year. Got 10 bulbs? That's £132.60 ....a year.

It is not uncommon to have 6 to 10 GU10/MR16 (downlight) bulbs in a kitchen or bathroom, at 50W each:

Replacing these with equivalent 5W LED bulbs would reduce energy costs by 90%.

But, be careful, know your Lumens and Kelvins.

LUMENS is the measure of the brightness of a bulb. This measure is key as bulbs vary in how efficiently they use Watts to produce light (Lumens). Fortunately it is now common to see a Lumens value on the packaging of bulbs. For reference, traditional incandescent bulbs produced the following light:

40W = 450 Lumens

60W = 800 Lumens

100W = 1600 Lumens.

KELVINS is the measure of the 'colour' of the light (technically actually it's 'temperature'). Traditional incandescent bulbs had a yellowy colour due to the nature of the way the tungsten 'burned' ​​​​​. That colour measures about 3,000K (Kelvins) or lower, and is typically referred to now as "warm white". For a much 'whiter' white; possibly in a kitchen where you want to clearly see your cutting board; look for 4,000-4,500K, which is typically now called "cool white". For retail premises, where you want very bright white light go for 6,500+, which is referred to as "daylight".

FINAL ADVICE: Buy bulbs in sets to ensure that all bulbs in a common fitting or room match up both in Lumens and Kelvins.