29th July 2016 Costs of charging devices

Costs of charging a mobile, laptop or tablet – power required and charging while on the move

As most of us rely on our mobile phones and other portable devices it’s important to keep them fully charged so they work when you need them. Some people charge devices overnight, some just plugin as soon as they wake up. But what does it cost and are you damaging the planet through excess carbon emissions? Generally it’s a good idea to be aware of how much power you are using and we have tried to calculate costs to demonstrate whether or where we can save.

Costs of charging a mobile and other devices

In the UK, we typically pay around 10p per kWh (kilowatt hour) of electricity. This is the standard measurement of how much your appliances and gadgets use. You can use a plugin power monitor to measure and record how much power your devices are drawing directly from a socket or other devices that can monitor the overall power usage by a household.

There are all sorts of benefits in reducing our power consumption to cut our bills and also carbon emissions to reduce the effects of climate change. That all seems well and good, but a house full of device dependent teenagers don’t necessarily think about these issues in detail.

It’s useful to be aware of how much our devices use and how much they cost.

What follows is little bit of maths, but pay attention and you will be reassured or horrified depending on how much you use.

As we said before, we pay around 10p or £0.10 per kWh for electricity in the UK (excluding standing charge and any extra taxes).

If you had a 1000 Watt rated bulb turned on for an hour, you would use 1 kWh and it would cost about 10p.

Just as an example, a typical kettle draws 2.2kW (2200W) and takes 2 minutes and 30 seconds to boil 1 litre of water, enough for four cups of tea.

This would need 2.2 kW x (2.5 / 60) hours = 0.092 kWh

This costs 0.092 x 10p = 0.92 p so 1p. So that’s 1p for a round of tea.

(Our eco-kettle will cost even less to run, check this link for more information – ECO kettles Energy saving kettles at ECO Arcade)

Costs of charging a mobile phone

A 2012 study at the Lawrence Berkeley National Laboratory found that an idle charger drew 0.26 watts on average; this figure goes up to 3.68 watts when a phone is attached and charging, and drops down to 2.24 watts when the phone is attached and fully charged (see http://cse.aalto.fi/en/midcom-serveattachmentguid-1e447ad5c817e3247ad11e4b55fb954807579d779d7/chargerenergy-cam01.pdf if you really want to read the whole paper).

So if you leave your phone plugged in overnight for 10 hours, then the phone would charge for about 2 hours and draw a current for about 8 hours while fully charged.

This adds up to 2 x 3.68 + 8 x 2.24 = 25.28 Wh

This is equivalent to 25.28 / 1000 = 0.02528 kWh

If your electricity costs 10p per kWh, then it costs 10 x 0.02528 = 0.25p per day.

Therefore the total cost for the year is about 0.25 x 365 = 91 p or nearly £1 for charging every day through the night for a year.Costs of charging devices

Costs of charging a laptop

Take the Dell XPS 13 as an example. It takes three hours to charge from empty to full. It has a 45W charger, so the calculation is as follows:

Total power consumption – 45 W x 3 hours = 135 Wh

This in kWh is 135 / 1000 = 0.135 kWh

This costs 10 x 0.135 p = 1.35 p per charge

Then the cost and power consumption depend on how often you use the laptop. Two or three times a week may end up costing £1.40 to £2 per year.

Costs of charging an iPad or tablet

The iPad Pro takes 4.5 hours to charge from empty to full. It has a 12W charger. So it will draw 12W for 4.5 hours, assuming you leave it powered off and don’t use it while it’s charging.

Total power consumption is 12/1000 x 4.5 = 0.054 kWh

Total cost per charge is 10 x 0.054 = 0.54 p per charge

When it comes to saving energy or costs, charging devices is way down the list of energy usage. There’s plenty of other areas such as lighting, heating, kettles, ovens, washing machines etc that you should look at before your devices. However charging multiple devices may add up so it’s a good idea to audit what you leave on and where you can make savings.

While eco gadgets such as solar powerbanks can cut electricity usage as they charge by solar energy, this feature is more important for the convenience and extra option for charging while on the move. They can be incredibly useful for giving you that 10 to 20% of charge to keep your device working when you need it.

See our range of solar powerbanks here: solar powerbanks.

Further reading

How much does it cost to charge your phone or tablet?

How much does it cost to charge a mobile phone or laptop

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