Your next computer can be any colour, so long as it’s green

Making power-hungry datacentres like these more energy efficient is vital. Schlüsselbein2007/Flickr

Do you have a computer on a desk somewhere? Fans whirring, screensaver flickering, left on for days. Would you leave your washing machine running for days? Because over time, a desktop computer draws on average a comparable amount of power to energy-hungry devices like a washing machine or kettle.

Yes, these use more power in the time taken to boil water or wash a load, but they are switched on and then off. A PC can be left to run for days, weeks, or months. And while your laptop may be more efficient, feel the heat blown from inside by high-speed fans or coming off the power adapter to appreciate the energy that is being used and lost.

You are likely to be spending £20 to £30 a year just for the convenience of not turning it on and off. Add to that all the other electronic devices in our homes, with televisions on standby, broadband routers, games consoles and phone chargers left running 24 hours a day, and the footprint grows.

Now take a step back and consider the IT infrastructure running in background: the network plumbing from the BT box in the street, through the local exchange, to warehouses full of whirring web servers. The scale is hard to comprehend. For example, giants such as Google, Microsoft, Facebook and Amazon are are among the world’s most popular websites. Behind these sites are datacentres packed with the hundreds or thousands of web servers needed to ensure their services stay snappy when millions of people Google or Facebook simultaneously. These datacentres are climate-controlled environments regulated by costly heating, ventilation and air-conditioning.

All this data-pumping and computer-cooling requires huge amounts of power. That’s just a few of the big players; every one of the world’s millions of websites is a computer in a room somewhere, plugged into the mains and left running day and night. The internet doesn’t switch off the lights and go home at the end of the day.

As most electricity is still produced from burning fossil fuels like coal or gas, that means IT contributes to the production of greenhouse gases such as carbon dioxide and methane that cause climate change.

Is it possible to define a computer user’s carbon footprint? One Harvard academic, physicist Alex Wissner-Gross [estimated](( running a couple of internet searches on a desktop computer generates 7g of CO2 - about the same as boiling a kettle.

More reliable estimates suggest the IT industry accounts for an estimated 4% (27 megatonnes of CO2 in 2011) of all UK greenhouse emissions, not far behind the airline industry which accounts for 6% (35 megatonnes in 2009). So the need to develop and move to greener, more efficient computing is very real – from handheld devices and desktop computers up to the data centres that feed our hunger for information.

This month, Greenpeace ranked Google and Cisco first on their Cool IT Leaderboard of energy efficiency. WHO Google recently pressured the local utility to provide it with clean energy. Last month, Hewlett Packard launched its HP Moonshot line of extra-low-power servers for use in datacentres.

This is green from an environmental perspective, but also preserves “green” of the folding kind - more efficient equipment requires less power and costs less to run.

To save battery life, your laptop is designed to power down the hard disk or slow the processor when the machine is idle. Despite all the energy expended at datacentres on power, cooling and lighting, servers typically run at only a third of their capacity. The rest of this power can be harnessed using virtualisation, where one computer can be configured as if it were several. This ramps up the usage on each machine and means fewer are required, a more efficient use of resources.

New manufacturing processes that use less resources to build computers, less toxic chemicals, and offer easier means to reuse components will cut pollution and wasted energy. Programmers can even write code that takes advantage of intelligent hardware to control processor speed and memory use in the most energy efficiently way possible.

But even if computers were twice as efficient, the national carbon footprint would only be 2% smaller. Far better to use computers to reduce the rest of our carbon footprint - the other 96% of energy usage.

Tele-conferencing, optimising travel and logistics, and just-in-time production are examples of where computers can reduce the need for resource intensive activity. The next generation of 3D printers will revolutionise manufacturing, leading to more efficient design, build, and transport of products.

In the meantime, buy the most energy efficient computer or portable device. Video-call with Skype instead of driving to a meeting (though convincing families to take a Skype holiday instead of flying abroad could pose a challenge).

And delete that message to “Please consider the environment before printing this email” from your email signature - because transmitting millions of those images of trees a day generates a carbon footprint of its own.