Carbon footprint and sustainability is increasingly important for all of us -- so how does the ecological footprint of your computing habits pan out?

The simplest thing you can do is to make sure that your desktop or laptop goes into sleep or standby mode when it's not in use. First up, make sure that you're not using a screensaver, or there will be little or no energy consumption difference between idle and in use. Next, KDE and Gnome both have menu items where you can set power preferences; or you can of course set things manually with various XF86 options, hdparm, and so on.

Next, consider whether you really need to leave your machine running overnight. If you run cronjobs overnight, try changing the timing to another lull time; or replace cron with anacron. You can also set up automatic shutdown if you tend to forget to turn the box off (I do). Both power management changes and overnight powerdown aren't just the green option, they're also the cheaper option: reduce your power bill!

Which machine?

So, assuming you're already running your existing machine(s) efficiently, what's the best type of machine to keep your eco-tech-footprint low? The figures show that laptops always come out ahead of desktops on power usage. However, it's not just about energy usage whilst in operation: there are other factors to consider, which are discussed in the next section. Netbooks can use even less power (2.5W for some recent chips; up to 10W for others) – but if you use your netbook with an external monitor you'll significantly increase this (an LCD monitor uses about 35W).

More generally, you can check out recent guides to buying energy efficient computers. Look for Energy Star rating, although be aware that this is a hardware standard; for it to actually have an effect you need to make sure your software is firing it up, which means setting the power management options as discussed at the start of this article. You can also use EPEAT, which rates laptops and desktops as Bronze, Silver, and Gold, to help you make your decision if you're buying.

When to replace?

So, should you dash out to replace your aging laptop with a lovely new ultra-low-energy machine? I've certainly seen it claimed that given the steady increases in power efficiency, it's financially worthwhile (in terms of energy consumption) to replace machines every 2-3 years.

The problem is, power usage isn't the only environmental issue associated with new computers. There's also the energy cost, and perhaps even more importantly, the resource cost, of producing a new machine. The EPEAT standard covers some of this when assessing the environmental performance of a machine, but the bottom line is: making new kit has an environmental cost.

There's also an end-of-life environmental cost to old machines. In Europe we now have the Waste Electrical and Electronic Equipment Directive, which makes manufacturers responsible for the environmentally-friendly disposal of their equipment at the end of its life. (As yet there's nothing similar in the US.) This may or may not be part of the reason why manufacturers have begun to develop more recyclable PCs! But even if consideration is given to recycling or non-landfill disposal, that too may have a human cost. (I note in passing that even if a machine is surplus to your requirements it may be useful to someone else: try to freecycle or donate to charity before you throw it out!)

This also brings up the lifespan issue. As discussed above, laptops use less energy in use, but they also tend to have shorter lifespans.

Next: Production and Disposal Costs »