Thursday, 3 September 2009

Watt is a pound a year?

We're exhorted to turn off unused devices in our house to reduce their standby consumption, and thereby reduce CO2 emissions from power stations. So it's tempting to ask what the cash benefit is, and the answer is surprisingly high. And there's an easy rule-of-thumb for working it out.

The amount that devices consume in standby varies widely. Older devices often didn't really have a standby mode - they just turned-off their front panel and pretended to be asleep, while still consuming a lot of energy. Evil! For example, one of the AlertMe crew discovered that his old black-and-white laser printer was consuming 60Watts, day and night, keeping the toner fuser warm. And hi-fi's, set-top-boxes etc. can easily consume 20Watts or more.
Even the latest gizmos can have a surprisingly high standby consumption. The colour laser printer I just bought, which has an Energy Star 2009 rating, consumes 17Watts in standby. And of course, it's not just the things on standby that matter - quite a lot of consumer devices are designed to be "left on" permanently, for example oil-filled electric heaters, which can be rated at up to 200Watts.

So what is a Watt, in money?

Well, thanks to a numerical co-incidence, at current electricity prices it turns out that every Watt left switched on for a year costs around £1.00.

So for example my new laser printer, if left switched-on for a year, would cost me £17. It makes little difference how much I actually use it, since the amount of use is tiny compared to the drip, drip, drip of the standby power, day and night, 24 hours a day.

The power rating of devices is usually to be found printed on the device, so for devices that are left plugged-in all the time, without a true standby mode, the number printed on the bottom corresponds to "pounds per year", as well as to Watts.