The maths of leaving your charger unplugged

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Leaving a mobile phone on charge costs next to nothing…right?

Now, we might be preaching to the converted and perhaps you never leave your mobile phone on charge once the battery’s full. But across the country, millions of people do, assuming it’s adding next to nothing to their electricity bill. Are they right?

Let’s do the maths

There’s a lot of debate about mobile phone charger energy use, and if you look hard enough you’ll find plenty of figures being bandied about. A quick and dirty experiment in the office involving Apple, Nokia, Samsung and Blackberry chargers and an energy monitoring socket showed there was little if any difference between chargers. So, for argument’s sake, let’s assume that a mobile phone charger on standby uses about 2 watts (W)† or the equivalent 0.0002 kilo watts (kW) of power.

If you were on our Standard electricity tariff, you’d be paying 15.897 pence per kWh and leaving your phone on standby for an hour would cost you around 0.03 pence.

Peanuts, isn’t it?

Well, it doesn’t sound much but let’s get hypothetical here. Many households today have adults and kids who own mobile phones. Let’s assume we’ve got a family of four, each with a phone that they leave on standby for 8 hours during any 24 hour period. Suddenly, we’ve got phones on standby for 32 hours a day and that’s costing 0.96 pence per day or £3.50 a year.

A waste of energy

So is £3.50 worth getting in a spin about? It should be, when you consider that our hypothetical family is just throwing it away, and there are millions of UK households doing exactly the same thing.

The bigger picture

In 2011 OFCOM reported that there were 81.6 million mobile subscriptions in the UK*. Using the same assumptions and rough calculations as those above, the numbers start to get a little scary.

81.6 million phone chargers left on standby for 8 hours a day use – or waste – 45,696,000 kW per year. That’s 125,194 kW a day. And, if we take some energy usage figures published by NASA** as a starting point (and why not?), that’s enough power for a town around the size of Canterbury, Cumbernauld, Bangor or Barry.***

That’s enough rough maths – here’s the even bigger picture

Clearly it’s worthwhile unplugging your charger to save energy, but let’s take a quick look at another part of the story. Buy a new mobile phone and it comes complete with charger. Which means your old charger takes its place amongst all the others in that kitchen drawer, before finally ending up as landfill.

Mobile company 02 estimates that there could well be 100 million unused chargers in UK homes.+ Their own customer research suggests that over 8 in 10 of us would be happy to receive phones without chargers.

And if you think in terms of annual UK mobile phone sales, that’s 24 million chargers that wouldn’t need to be produced, packed and shipped – saving a huge amount of energy.

“If only mobile phone makers could agree on a universal charger…”

Funny you should say that, because here’s the good news. Ten major companies including Apple have signed a European Commission Memorandum of Understanding (MoU) to do just that. No dates have been agreed, but before too long, we may all be using the USB port to charge our phones.

In the meantime, think of Canterbury, Cumbernauld, Bangor and Barry and unplug that charger!