Light bulbs have gotten complicated in the last few years. It used to be that a forty watt light bulb was a forty watt light bulb, and that is all you needed to know to find a replacement. Judging by all the facts and figures on the packaging now, you need a physics degree to find the right bulb. But it is not as complicated as it seems. What’s the key to figuring it all out? Lumens.
The watts on a light bulb tells how much energy the light bulb uses, not how bright it is. When the only light bulbs available were incandescent light bulbs, watts was a good way to tell how bright a bulb was. But the newer kinds of bulbs (LED, halogen, compact fluorescent) use less energy to produce light. So a forty watt halogen bulb is brighter than a forty watt incandescent. Then what is the best way to compare the brightness of two bulbs? The answer is Lumens. Any bulb that says it gives off one hundred lumens will be the same brightness, regardless of how many watts it uses.
Another measure of light is the color. Light can be any color but black. What we call black light is actually violet. It’s confusing because yellow, orange, and red light are called ‘warm’ light, and green, blue and purple light we call ‘cool’. The scale you see on light bulb packaging to describe the color of the light is the Kelvin scale. Higher numbers on the Kelvin scale are cool (bluish), and lower numbers are warm (reddish), with white light at about 4500 Kelvin.
Finding the Right Light Bulb
So, to find the right bulb you have to look at the lumens for brightness, and the kelvin for color. None of the other figures, like life hours, or year life, or watts, or estimated savings, have anything to do with the quality of the light the bulb produces. They all refer to how long the bulb will last, or how much energy it uses, or how much money it costs to run the bulb. And the best way to get the correct replacement bulb, is to bring the old bulb with you went you are looking.