Demand: Gadgets 1
Electrical Gadgets
This worksheet covers
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Cost of electricity
Why and where we use gadgets
Typical power consumption of gadgets
Life cycle energies for an energy-using product (a hairdryer)
Calculation of energy a mobile phone charger uses when left plugged in
The number of energy-consuming gadgets that we use is growing rapidly each year. By knowing which gadgets
consume the most energy we can save money, as well as help the environment.
Cost of electricity
The amount of mains electricity a gadget consumes depends on its power (normally specified in W) and the
length of time it is plugged in for. Electricity meters in homes and buildings show how many units of electricity
have been used in kWh, a unit of energy:
Energy (kWh) = Power(kW) x Time(h)
Electricity currently costs roughly 12p per kWh in the UK
Why do we use gadgets?
We use gadgets for many reasons, including:
• Entertainment
• Communication with others
• Making our lives easier
• Education
• Work
Demand: Gadgets 2
Electrical Gadgets
Entertainment
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Television
DVD players
CD Players / Stereo Systems
Games Consoles
Personal Computers
etc
Communication
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Making our lives easier
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Dishwashers
Washing machines
Tumble dryers
Answering machines
Internet
etc
Land line telephones
Internet (email, social networks etc)
Mobile phones
etc
Electrical Gadgets
Demand: Gadgets 3
Work
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Dual screen displays
Teleconferences
Printers
Scanners
Photocopiers
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Dictaphones
Electric pencil sharpeners
Projectors
Air conditioning
etc
Education
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Personal computers
Overhead projectors
Interactive white-boards
etc
Demand: Gadgets 4
Combining Gadgets
Gadgets such as smart phones
incorporate many different
technologies that would
previously have required
several energy consuming
gadgets.
Electrical Gadgets
Demand: Gadgets 5
Electrical Gadgets
Power Consumption Of Gadgets
Typical power consumption of various gadgets (units: W) (note actual values vary between models and can be found
on the appliance or in the owners manual)
Gadget
On and active
On and inactive
Standby
Television
100
6
10
DVD player
7
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5
Digital TV set top box
6
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5
Sony PS3
190
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2
Nintendo Wii
18
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2
Digital Radio
9.1
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3
Desktop Computer
80
55
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Cathode Ray tube Display
110
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3
Projector
150
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5
Laser Printer
500
17
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Laptop
16
9
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Mobile Phone Charger
5
0.5
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Dishwasher
1000
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Washing machine
800
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Electrical Gadgets
Demand: Gadgets 6
“Energy-using Products”
New EU regulations encourage (but do not require) manufacturers to consider the environmental impact of all
products that consume energy. It was noted in Introduction: Life Cycle Analysis that in almost any energy-using
product, it is the Use phase of the product life cycle that dominates its environmental impact. This is demonstrated
below for a common household appliance: a hairdryer.
Life cycle analysis of a hairdryer
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2000W hairdryer weighing 890g, manufactured in southeast Asia
Transported to UK by ship for approximately 20,000km.
Lifetime of 3 years
Used 150 days per year for 3 minutes per day
Materials 100% recycled at end of useful life
The table summarises the energy associated with each phase in the life cycle of a hairdryer (from Ashby, 2009):
Energy (M J)
Percentage (%)
Material
72
11
Manufacture
6.8
1
Transport
89
13
Use
506
75
Total
673
100
It is clear that the Use phase dominates: 75% of the impact comes from the electricity consumed.
Demand: Gadgets 7
Electrical Gadgets
Is it worth turning of a mobile phone charger when it’s not in use?
From the table of typical values we can see that a charger that is plugged in but not charging a phone uses 0.5W.
Therefore, if left on for one day it uses:
0.5W 24 hours = 12 Wh per day = 12/ 1000 kWh per day = 0.012 kWh per day
A typical person in the UK who uses 200 kWh per day, so turning off a phone charger will save:
(0.012/200) 100% = 0.006% of their energy use (not very much!).
Cost-wise, assuming electricity costs 12p per kWh, leaving a charger plugged in when not in use will cost:
0.012 kWh/day 12p/kWh = 0.14p per day
These simple calculations show that leaving a charger plugged in isn’t going to make a large difference to our
energy consumption. This is not to say it shouldn’t be turned off, just that there are far more significant changes
that can to be made. To put this in context:
- the energy saved in switching off a charger for one day will be used up in one second of driving!
- the energy saved in switching off a charger for one year will be used up in one hot bath.
Can you do the equivalent calculation for turning a television, DVD and set-top box off standby?
What about turning off all your school’s desktop PCs, laptops and laser printers overnight?
Future of gadgets
It is likely that our reliance on, and use of, gadgets will increase in the future. However they are also becoming
more efficient all the time. Therefore it is hard to know how our energy use in terms of gadgets will change.
What do YOU think? Could you manage with fewer gadgets, or use them more efficiently?
Demand: Gadgets 8
Electrical Gadgets
Sources
MacKay DJC, 2009. Sustainable Energy – without the hot air, UIT Cambridge.
Also available free online from www.withouthotair.com
Ashby MF, 2009. Materials and the Environment, Butterworth-Heinemann.
Granta Design Ltd, 2011. Cambridge Engineering Selector (CES) Database.
Images from www.sony.co.uk, www.apple.com/iphone, http://npdbook.com