While visiting Kingston upon Thames yesterday, I notice a new shop had opened in the premises that used to house Woolworths. I found the shop – Clas Ohlsen – rather hard to classify. It was somewhere between a hardware store, an electrical retailer, a stationer, with a few ‘gadget’ sections. I bought an extremely cheap energy meter (£5.99 on special offer) but it was not until I got home and browsed their catalogue that I realised how much I liked the shop.
On looking at their light bulb section, they had a very clear guide to the different lighting types, and most importantly they stated the number of lumens that each bulb emitted. A lumen is a measure of the amount of light emitted by a bulb as it will be perceived by people. A physical unit which incorporates human perception is rather unusual, but undeniably useful. I had despaired that this information would ever be available on the packaging of light bulbs. It means that I can see that LED light bulbs – now readily available – give out 50 to 70 lumens per watt of electrical power; energy saving light bulbs give out around 40 to 60 lumens per watt; halogen light bulbs give out 12 to 18 lumens per watt and regular incandescent bulbs give about 10 to 12 lumens per watt. NOw I can make rational choices.
Interestingly the guide also gives clear information about when the different classes of light bulb will be phased out; details of dimmable energy saving bulbs and the temperatures at which energy saving bulbs will work – with special bulbs available for outdoor use. Why did it take so long for a shop to simply give people the information they need.