Updated Mon 27 Mar 2017
My largest energy use is the web servers that run client websites 24 hours a day. I:
100% renewable since 2011 – supplier: Ecotricity.
(I also buy gas from them, as of March 2017 only 5% of that is "green" – bt that will increase significantly once they complete build of anaerobic digesters.)
This currently isn't green energy and it's complicated to calculate the usage (more details below.) Until I can move to a greener datacentre (I think I may now have found one), I've chosen to offset my small estimated carbon-footprint several times over.
TL;DR: My datacentre energy usage is pretty low, but very hard to calculate precisely due to lack of public information.
Most of my webservers are hosted by Linode, at Equinix Telecity's Powergate datacentre in Acton, West London.
All direct datacentre customers (i.e. those who leasing cages or racks from the datacentre operator) are billed on multiple criteria including power usage in amps. So it's in Linode's interests to keep consumption as low as possible, by selecting modern, power effiicient components. They don't reveal details of all their exact hardware (this is quite common), but they are using Intel® Xeon® E5-2680v3 processors - these are very new - the CPU in a server is usually by far the biggest power drain (except for a spike when you first switch it on.)
Linode also only use SSDs, which (generally) have lower power consumption than spinning disks. They use DDR4 RAM, which is roughly 30% more power efficient than DDR3, running at a slightly lower voltage.
The datacentre is certified to ISO 50001 and its very energy efficient (a PUE of 1.35 with a modern cooling system, waste heat used to heat office space, rainwater harvesting, motion-activated lighting and Carbon Trust Standard certification.) Datacentres use around 2.5% of European electricity, so a lot of work is going into energy efficient design.
However, currently only 20-25% the data centre's electricity comes from renewable sources.
Greenpeace Click Clean report gave Telecity a mix of C/D grades, which I'd call "middling". (This is from their 2015 report, as of March 2017 that's the most recent.)
I also use Amazon Web Services: specifically their S3 and Route 53 products, for backups, DNS and some web hosting of media/assets. In April 2015, 25% of Amazon's energy use was renewables, their target is 40% by December 2016 and they have a "long term" goal of 100%. My AWS usage is much lower than for the VPSs, as it's mostly data storage and low intensity work like responding to DNS queries. I also use AWS Glacier – its designed for infrequently accessed files – Amazon remain very secretive about how Glacier works, but the technology we think they're using is almost certain to need less energy.
As you can see, it's impossible to calculate an accurate carbon footprint when so many companies are involved and so much of it isn't in the public domain.
Occasionally they do provide information. For example, I use Gmail, and Google have calculated the average power consumption per Gmail user is 2.2 kWh per year.
Based on info from Linode's CEO (these are 2008 figures based on US voltages!) a particular size of VPS uses about 7.5 watts, or 65 kWh a year, which is roughly 0.03 tonnes of CO2 (using the average UK grid energy mix).
This would mean the servers I'm responsible for generate about 0.25 tonnes a year.
However, this doesn't include all the other infrastructure, e.g. air-cooling, the use of the backup server, the data centre building, the fuel in the backup generators etc. or the energy used in equipment manufacture and datacentre construction.
As the figures have so many caveats and I'm using relatively little energy for business work, I've decided to just offset a much greater amount:
Why these charities?
Both the World Land Trust and Trees for Cities are UK based, established in 1989 and 1993 respectively. Their staffing levels are modest and they don't use aggressive fundraising tactics.
World Land Trust assists overseas NGOs in purchasing land (over 500,000 acres so far) for small-scale sustainable development. Rather than save specific species, controlling the land means the whole ecosystem is protected. Its patrons are David Gower, Chris Packham and Sir David Attenborough.
Trees for Cities has projects around the UK, especially in London. They combine tree-planting with education and community work. It's supported by Jon Snow, Alistair McGowan and others.
My desktop computer is a 2012 Apple Mac Mini. Apple describe this as "the world's most energy-efficient desktop computer", although you should remember it doesn't include a display (see below). A priority for me was something that used minimal energy when in standby (1.25W) but can wake up instantly when needed, without having to reopen applications or restart virtual machines.
You also want a computer that will last a good number of years – 67% of the greenhouse gas emissions for the Mac Mini are from manufacture and shipping, and that's assuming a full four years of ownership. (I've had mine since November 2012).
The Mac Mini has some environmental and practical advantages over other Apple products:
I bought the highest specification available at the time Apple refreshed the product line, with the view to using it for as long as possible: I'm hoping until at least 2018/2019, the only constraint is disk space and I plan to migrate some content over to external SSD. Besides anything else, upgrading a computer is time-consuming: there's the decision fatigue in choosing a new device and, despite migration tools, a lot of software inevitably needs to be reconfigured. You're also forced onto the most recent version of the operating system, which may be buggier than you'd like, and nowadays MacOS upgrades usually only offer marginal benefit as most of the features you need have already been added - the value typically comes from updates to third party software which can usually run on previous OS versions.
The Dell display meets various environmental certifications including EPEAT Gold. I can almost always comfortably use it with the brightness on the lowest setting (there's an energy gauge built in) and my measurements show it's usually using less than 10 watts. Would recommend, though occasionally I wish I'd chosen a larger one (not that often though). I don't feel I've lost out in any way by not having a retina display - HD video at 24" is still very sharp. Having a separate display rather than an iMac also makes it easier to adjust the height / exact position.
I use USB-powered WD My Passport drives for backups, these automatically spin down when not in use (and I've reduced the OS X TimeMachine scheduled backup interval from every 1 to every 3 hours.) Any future drives I purchase will be SSD to increase speed, provide equal or longer MTBF and reduce energy use.
Any 2015-2016 business transport was by train / underground (approx 0.01 tonnes of CO2 annually.)