The original low energy light bulbs are compact fluorescent lamps (CFL). These are four times as efficient as the incandescent light bulbs they replaced. They have several problems:
They can take time to switch on and minutes to get to full power.
Over time they get less bright, especially when just turned on. This together with, I think, over optimistic labelling of the wattage of the incandescent they replaced has made us think they are not a good as incandescent light bulbs.
They contain Mercury.
New low energy light bulb are now available, LED bulbs. LED stands for light-emitting diode. These are now available as standard bayonet (B22) lamps for about £7 in local shops and on line. LED bulbs have the following advantages over CFL lamps.
They are even more efficient the CFL, using at least 30% less power for the same brightness.
They are instant on. They do not need time to warm up.
The do not contain Mercury.
They should last 3 times longer than CFL lamps and 25 times that of a standard incandescent bulb. Like CFL LED may get less bright over time but at least 3 times slower than CFL.
How is the brightness of a lamp measured? In the old days when we only had incandescent light bulbs they we measured by the power(electricity) they consumed in Watts(W). This was OK when there were only one type of bulb, and for incandescent it was a good enough measure. When CFL came along they were described by the wattage of the incandescent equivalent. In my view some what optimistically. Now LEDs and other bulbs have come along and we are stopping using incandescent equivalent as this has got ridiculous, so now bulbs are described by how bright they are, this is measured in Lumen. They still also state the power in Watts they use. So the efficiency of a bulb can be measured by lumens/watts.
The standard B22 LED bulbs that are common now come in two brightnesses 450+ and 800+ lumens. These are equivalent of the old incandescent 40w and 60w, I think now pessimistically rated. I tried an 810 lumen LED light in my landing and it was too bright.
I am not sure there is an argument for replacing existing CFL with LEDs ahead of when you would replace the CFL. But due to the longer life and less electricity consumed by LED bulbs, for both economic and environmental reasons we should stop buying any more CFL bulbs and buy LED bulbs. And LEDs are better bulbs.
Above I was talking about standard bayonet bulbs, but the most inefficient in our houses these days are normally halogen bulbs. These are another form of incandescent light bulbs they are found in GU10 spot lights, normally in kitchens and bathrooms.
LED GU10 have been available for a few years and given that LED are more directional than halogen they only need about 1/8 the electricity to produce the same effective light. Some of the early LED GU10 were a bit dim. But any current LED GU10 over 400 lumen (5W) should be a good replacement for 50W incandescent. Given that LEDs last at last 10 times longer than halogen the conclusion is again only buy LED bulbs, but with halogen there may be an economic and environmental argument to replace existing bulbs with LED.
Another reason to replace all halogen with LEDs is that a lot of them are on when the electricity demand is at it's highest, 6pm on a winter's evening, and the reduction in peak grid demand would save building at least one new power station.
Halogen bulbs are also found in outside flood lights and these can be replaced by LEDs.
Notes on LED bulbs:
Not all LED can be used with dimmers but ones that can are available sometimes at a slight extra cost.
LED bulbs can come in different colours warm white or bright white. And if you pay more any colour you like and some even changeable by remote control.
This article first appeared in our March to June 2015 Newsletter and on iccaldwell.com