James O'Neill's Blog

May 4, 2006

Save the Planet with a little at a time with Windows Vista

Filed under: Windows Vista — jamesone111 @ 10:00 am

You may have heard claims about how Vista can help you save electricity. It has 3 features which play a role in this.
Firstly it’s “Sleep” and Hibernate modes work better than their equivalents in XP – various things have lost their veto over Hibernation.
Secondly the machine can “wake” from it’s sleep state to run a scheduled task, so you don’t need to leave PCs on overnight for software updates, disk de-frags, virus scans and the like.
And Thirdly we’ve added power to the set of things which can be centrally managed with group policy, so PCs which are left on 24/7 and spend most of their time running screen savers can now be powered down.

The numbers go like this,
There are 8760 hours in a year, and a PC only needs to be on 10 hours per day 5 days a week = 2600 hours a year. So those 24/7 PCs could be in sleep mode for 6160 hours per year. [That’s the basis we use, and I think the savings are bigger – a PC isn’t used from 8AM till 6PM in most offices, it can power down when we’re away in meetings or at lunch, and we don’t come into the office 260 days a year… you might have a further 1000 hours of sleep. Those PC produce heat – reduced it, and you reduce air conditioning requirement too]
A PC and monitor use about 125 Watts when running and 5 Watts when on standby a saving of 0.12KW. Multiplied by 6160 hours per year that’s 740 KWh per year. The national energy foundation have a useful “calculate your CO2 emissions” page which says 1 KWh of electricity makes 0.43 Kg of C02, so 740 KWh is about 1/3 of a tonne of C02. Multiply by the number of PCs you have and it’s quite a big saving.

I found a paper from the UK parliament which makes that about 3% of the average C02 emissions per person here – France emits less Co2 than us – because their electricity is mostly nuclear, so their Co2 saving will be less. US emits twice as much (4.6% of the worlds population contributes 23.8% of green house gasses) so they need all the savings they can find.

It’s hard to estimate the number of “Sleep hours” we can get (how many PCs run 24/7 ? What can it be reduced to ?), and I don’t have a world wide average for C02 emissions per KWh, and I can’t predict how much power an average PC will consume in the future … but with hundreds of millions of PCs, saving hundreds of Kilowatt hours, that makes tens of millions of tons of C02 – equivalent to whole output of a small country. Doing something about global warming means both big changes (like electricity generation) and small ones (in its consumption). This is a small change, but as the Chinese proverb has it, “The Journey of a thousand miles starts with a single step”

This post originally appeared on my technet blog.


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