How much power does a computer use? And how much CO2 does that represent?

The power consumption of a computer varies depending on whether it is a desktop or a laptop:

• A desktop uses an average of 200 W/hour when it is being used (loudspeakers and printer included). A computer that is on for eight hours a day uses almost 600 kWh and emits 175 kg of CO₂ per year.
• A laptop uses between 50 and 100 W/hour when it is being used, depending on the model. A laptop that is on for eight hours a day uses between 150 and 300 kWh and emits between 44 and 88 kg of CO₂ per year.
• In stand-by mode the power consumption of both a desktop and a laptop falls to about a third. This contributes to the 'vampire draw' of your household.

Remember that stand-by mode uses power, too!

The power consumption of a computer of course depends on the model and the way it is used. For instance, a laptop only uses a third as much as a desktop:

• A complete desktop uses an average of 200 Watt hours (Wh). This is the sum of the average consumption per hour of the computer itself (171 W), the internet modem (10 W), the printer (5 W) and the loudspeakers (20 W). Assuming that a computer is on for eight hours a day, the annual consumption comes to 600 kWh. That corresponds to CO₂ emissions of about 175 kg per year, i.e. 1.75 % of the average annual emission of a Belgian.
   
• A laptop uses considerably less: between 50 and 100 Wh that it is on, depending on the model. If it is used for eight hours a day, consumption therefore varies between 150 and 300 kWh/year. That corresponds to CO₂ emissions of between 44 and 88 kg per year (or between 0.44 and 0.88 % of the average annual emission of a Belgian).
   
• On stand-by, the power consumption of both a desktop and a laptop computer falls to about a third. Putting the monitor on stand-by reduces its consumption by 15%. If the monitor is switched off completely, then of course it does not use any power.
   
• Although the internet is a virtual space, using it still requires power and results in CO₂ emissions. Think about it!

Some tips to save energy

1. Switch off the loudspeakers if you are not using them.
2. Switch off the printer when it’s not needed.
3. Switch off the screen if you are not working on the PC just now.
4. Switch off your computer or put it in stand-by mode if you are not going to work on your PC for more than 30 minutes. A multiple socket makes it easy to switch off all your computing equipment.
5. Use a laptop in preference to a desktop.
6. Switch off the modem at night.