Thursday 22 April 2010

Where Has All The Power Gone?

My better half is a bit of a green eco-warrior and is constantly complaining about our energy usage, in particular, the plethora of devices we leave in standby mode.

One old chestnut is the amount of electricity used by a TV in standby mode. I've maintained that this "over-reaction" is a legacy from the days when television manufacturers used to push features to allow TVs to present a picture as soon as possible after "turning on". Indeed, Toshiba were still including such a feature in its LCD Regza range in 2008:
  • Power-on: 218.08 Watts
  • Stand-by: 0.58 Watts
  • Fast turn-on: 17.8 Watts
What were they thinking?

It turns out that most devices in this category consume less than 1W in standby and this includes appliances such as cookers and microwaves that have digital clocks. But that still potentially amounts to 8 or 9kWh per year.

Another chunk of energy is used by devices that are always on, such as security alarm systems, central heating controls, telephones and broadband modems. Of these, telephones and modems are "actively working" pretty much 24 hours a day, even if they aren't doing anything constructive for the majority of the time.

We recently borrowed an electricity monitor to try to put some concrete figures together. It turns out that our minimum, background energy usage is 200W, but this flicks up to 300W when a fridge/freezer compressor kicks in or we turn some lights on. Boiling water, washing clothes and watching television are definite no-nos, but alas, we do all these things, so our average daily consumption has been 12kWh. I'm sure it would be possible to get this figure below our (self-imposed) initial target of 10kWh, but not without significant behavioural changes. So I'll be lazy and use statistics instead.

The World Bank suggests that, per capital, Britons consumed 6120kWh of electrical power in 2007. That, of course, includes electricity used outside the home on our behalf. Our household usage of 12kWh per day equates to about 2200kWh per person, per year. So meeting our target by reducing our personal usage by 16⅔% would only reduce our total per capita usage by 6%. Well done, Amdahl!

To play devil's advocate, I propose a new metric which factors in the inconvenience of saving energy in the home: the kilowatt-hour-cumber.

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