The average PC takes 1.8 tonnes of chemicals, fossil fuel and water to manufacture and causes the emission of 100 kg carbon dioxide each year, but most of us simply couldn't live without one.

Unfortunately, computers are becoming more power-hungry as we expect them to perform increasingly complex tasks for us.

Power drain

Desktop PCs that are plugged in all day are especially power-hungry.

Unless you flick the switch on the wall or take the plug out of the wall a PC that is apparently turned off will still be using power.

If you leave your computer monitor on all night you'll waste enough energy to microwave six dinners.

A PC left running 24 hours per day would use £59 worth of electricity over a 12-month period and create 716 kg of carbon dioxide emissions a year.

Small is beautiful

Laptops need to be as energy-efficient as possible so that they can go anywhere.

The processors are designed to run on less power, the screens use as little energy as possible, all of which adds up to significant energy savings compared to a desktop PC.

Energy-saving tips

Unplug your PC when not in use, and don't forget the scanner, monitor, printer, broadband box and audio speakers all need turning off too.

Use your computer's energy-saving mode: you should be able to turn the brightness of the screen down, or set it to turn off if you haven't used it for 5-10 minutes.

The National Renewable Energy Laboratory has a guide to how to do this.

This article is based on an extract from Friends of the Earth's book How Can I Stop Climate Change?