It has been a bitterly cold winter. The temperatures have regularly been on the wrong side of freezing, and the sun has generally set by the time I leave the office. The result is that when I get home in the evenings, the first thing I do is switch on every light and heater available, switch on the electric blanket, and start cooking a nice warm meal on the stove.

With all these appliances and lights burning, it got me thinking about the importance of using energy efficient appliances and lighting. I hope to unpack the latter in this article.

A “normal light bulb” is also known as an incandescent light bulb. These are the bulbs that we all grew up with that have a very thin filament inside a glass sphere. They typically come in sizes like “60 watt,” “75 watt” and so on.

The basic idea behind these industrial-age bulbs is simple. Electricity runs through the filament and because the filament is so thin, it offers resistance to the electricity, and this resistance turns electrical energy into heat. There is enough heat to make the filament white-hot, and white-hot equals light.

The problem with incandescent light bulbs is that the heat wastes a lot of electricity. Heat is not light, and the purpose of the light bulb is to produce light, so all of the energy spent creating heat is wasted. As a result, incandescent bulbs are very inefficient.

But there is an alternative! Thanks to the compact fluorescent bulb, lighting has been one of the great success stories in energy efficiency in the last decade. Like the fluorescent lamps found in commercial buildings, a compact fluorescent bulb is a tube. However, the residential versions are narrower and twisted around like a koeksister.

Below is a table of typical compact fluorescent bulbs and the equivalent incandescent bulbs used to produce the same amount of light:

Compact fluorescent bulbs	Incandescent bulbs
7 watts	25 watts
15 watts	60 watts
18 watts	75 watts
27 watts	100 watts
32 watts	150 watts

A fluorescent bulb uses a completely different method to produce light. This is a trick similar to the one used by creatures like fireflies and glow-worms, whose bodies contain chemicals that make “cool light” without any heat. There are electrodes at both ends of a fluorescent tube, with various gases inside the tube. A stream of electrons flows through the gas from one electrode to the other. These electrons bump into the mercury atoms and excite them. As the mercury atoms move from the excited state back to the unexcited state, they give off ultraviolet photons. These photons hit the phosphor coating on the inside of the fluorescent tube, and this phosphor creates visible light. It sounds complicated, and without a scientific background, it probably is! The important thing is that the end result is an exceptionally efficient source of light.

There is only one drawback with compact fluorescent bulbs, and that is that they cost a lot more than incandescents. The upside to the higher cost is that they last a very long time. The expected lifetime of most compact fluorescent bulbs is 10,000 hours. In contrast to the long lifetimes of compact fluorescent bulbs, incandescent bulbs are rated to last from 800 to 1,000 hours. It would take 10 or more incandescent bulbs to match the life of one compact fluorescent.

If you decide to get on the energy efficiency bandwagon, lighting is an obvious and easy place to start. So have a look around your house at your existing choice of bulbs; you might just see the light at the end of the energy efficiency tunnel!