Updated Tue 19 April 2016
My largest energy use is the web servers that run client websites 24 hours a day.
100% renewable since 2011 – supplier: Ecotricity.
(I also buy gas from them, at present only 5% of that is "green" – will increase when 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.
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 it's 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.
(Source: Greenpeace's latest Click Clean report – in 2015 they gave Telecity a mix of C/D grades, which is middling.)
I also use Amazon Web Services (for backups, DNS and occasional hosting of static files.) 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 – it's 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, I've decided to simply 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. It's 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 remember it doesn't include a display. It's important to choose something that uses minimal energy when in standby (1.25W) but can wake up quickly when you need it.
Even more importantly, you need 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 based on four year's ownership.
The Mac Mini allows you to choose your own peripherals - this means I can retain the screen, keyboard, mouse/trackpad etc. when upgrading, rather than having to replace the complete system. (I'm using a keyboard from my previous iMac.)
Another reason I chose it: were it ever to go wrong, it is easy to transport for repair (or for use at another location.)
I'm hoping it will easily be powerful enough for another year or two.
I have a Dell U2414M display, which meets various environmental certifications including EPEAT Gold. I can almost always comfortably use it with the brightness on the lowest setting (the brightness setting has an energy gauge built in) and it consumes little more than 10 watts.
I use USB-powered WD My Passport drives for backups, these spin down when not in use.
All 2015 business transport by train / underground (approx 0.01 tonnes of CO2)
UPS recently introduced a carbon neutral shipping product – I hope to use this for any future packages I send.