Energy Use in Computing

Every device that runs uses electricity. Much of it is still generated by burning fossil fuels such as gas and coal, which releases carbon dioxide (CO2), a greenhouse gas that contributes to climate change.

Devices waste energy when left on unnecessarily. A computer on standby still draws power, and older, inefficient hardware often uses more electricity for the same job than a newer machine.

Data centres

A data centre is a building full of servers that store data and run services for customers. The services must be available whenever customers need them, so the servers, network links and backup power run almost continuously. Servers produce heat, so cooling systems use even more electricity and also use water, which makes data centres a large part of computing's energy use.

Reducing energy use

Energy-efficient hardware cuts energy use: a processor that does more work for each watt, or a monitor that uses less power at the same brightness. Power-saving settings help too, such as making a computer sleep after a few minutes of inactivity, dimming the screen, and switching off at the wall instead of leaving a device on standby.

Organisations can share efficient servers in a data centre instead of each running their own small server room, because one large, well-managed data centre can power and cool many servers more efficiently than dozens of separate rooms. Data centres can also buy renewable electricity from wind or solar farms and design the building to need less cooling, for example by arranging the racks so air flows freely between them and by capturing waste heat to warm nearby buildings.

For example, a school with 120 computers and monitors might leave them on for 4 extra hours a day. If each computer and monitor together uses 80 W, that is 120 × 80 × 4 = 38,400 Wh, or 38.4 kWh, of wasted electricity every day, so switching off at the wall after the last lesson avoids that waste.