Energy Consumption During Use

Energy consumption during use is the electrical energy a digital device takes from its power supply while it is working or charging. A smartwatch on your wrist, the tablets in a classroom trolley and a handheld games console all need a steady supply of electricity to run their processors, screens and wireless connections.

Where that electricity comes from

Electricity reaches your socket through the mains, but it has to be generated first. A common method is to burn fossil fuels such as coal, oil and gas in a power station: the heat boils water into steam, the steam spins turbines, and the turbines drive generators. Burning the fuel releases carbon dioxide, a greenhouse gas that traps heat in the atmosphere and contributes to global warming and climate change.

So every unit of electricity your device uses usually means a little more fuel burned and a little more carbon dioxide released. Where electricity is generated from wind, solar or hydro power instead, the same device causes far fewer emissions, which is why how the energy is generated matters as well as how much is used.

Why the amount of energy matters

The more power a device draws and the longer it is left running, the more electricity has to be generated. If that electricity comes from fossil fuels, more fuel is burned and more carbon dioxide is released. Devices left on standby still draw a small current, so a device that looks switched off can keep adding to emissions hour after hour.

Worked example: a school leaves a trolley of 30 tablets charging overnight when only 5 are needed the next morning. The other 25 are charged for nothing. Each tablet uses only a small amount of electricity, but across a school year and across thousands of schools that wasted electricity has to be generated, so extra fossil fuel is burned and extra carbon dioxide enters the atmosphere.