Features

The increasing concern about the state of the planet and the part we play is causing the electronics industry to rethink its practices. Manufacturers are going to great lengths to secure greener credentials for everything from processors to packing cases. When a hip company such as Apple starts using its environmentally friendly practices as part of its marketing, it's clear that a trend is being set.

However, there's more to saving the world than making sure new products are manufactured in a responsible way. Our existing electronics, and how we use them, can also play a part. Even if you are not convinced about your contribution to climate change, paying closer attention to how you use your gadgets will save you something else - money.

Obviously it costs money to run or recharge anything from the mains power supply, but that's only part of it. You may be happy to pay for the privilege of using a PC, laser printer, television or DVD player for several hours each day, but should you be paying for them to sit idle the rest of the time? The standby mode of many devices does little more than curtail external signs of activity while leaving the internals to draw almost as much power. The question is: what practical steps can you take to fix this?

The simple option is to turn off an electronic device at the mains when it's not in use. Unfortunately, it's not so easy in practice when certain devices such as video recorders need to turn themselves on at certain times. A more viable option

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is to establish just how much it costs to run your key power consumers when they're not being actively used, then ensure that they stay in their lowest power state for as long as possible. In this feature, we'll show you how you can do this.

Testing and Calculations

Unless you're in the enviable position of not having to worry about your utility bills, it's good financial sense to ensure you're getting the best value out of your energy consumption. Luckily, when it comes to electricity, this is easily done. A £10 gadget that sits between the mains supply and an electrical device can, in a few seconds, tell you how much power that device uses in its active state. It can also show the effect of any power-saving measures.

For the purposes of this feature we used a power plug monitor, available for £9.95 including VAT from Maplin Electronics. This isn't a scientific instrument that can measure power consumption down to the nearest nanowatt, but its accuracy is more than sufficient for home use. This particular model can measure a variety of units, but the one of interest to us is the watt hour.

The watt (W) is the standard derived unit of power. In essence, it's a measure of how much energy a device consumes when it is working. A watt hour is the number of watts consumed each hour by, in our case, an electrical device. For example, a 100W light bulb is so termed because it draws 100 watts over one hour. If you know how many watt hours a device consumes, multiplying it by 1,000 gives its kilowatt hour rating. Armed with this information, you can then calculate how much the device costs to run, since all utility companies charge by the kilowatt hour (kWh). They usually refer to one kWh as a unit.

At the time of writing, the lowest priced electricity cost 11.087p for the first 900kWh (900 units), then 7.036p for the rest. So if our 100W light bulb is left running for six hours a day, that equates to 100x6=600Wh a day, or 0.6kWh. At a cost of 11.087p per kWh, that means that the bulb costs almost 7p a day to run, which is around £24 a year.