Blog post

How green is your digital footprint?

Energy Blog, 8 April 2020

The amount of CO2 you are saving by your valiant attempts to use reusable coffee cups is probably undermined every time you hit reply all and attach a video of that parrot to your company wide email.

The first commercially successful copy machine, the Xerox 914, was a red-hot new technology back in 1959 – so hot that the machine shipped with its own fire extinguisher due to its tendency to catch fire. The company labelled this accessory the “scorch eliminator”, but despite this, the copy machine went on to become one of Xerox’s most lucrative products.

Things have come a long way (and are hopefully safer) since then and we eagerly await the next technological step, the promise of the paperless office. This new utopia has been just around the corner since the mid-1970s. Going by the stacks of paper covering the desks of many there is still a long way to go, however email has at least made a big difference.

Does your annoying “reply all” email habit actually contribute to global warming?

The average person sends and receives 126 emails per day, resulting in 300 billion emails sent daily worldwide. Those numbers sound like impressive progress and imply that we have become enormously productive. Has technology enabled us to be more efficient and responsive, or encouraged us to be less concise? I suspect it is more likely that we just cannot resist the temptation of the reply-all button. Emailing ones and zeros consumes energy whenever those messages are transmitted, viewed, replied to, stored and backed-up. The carbon footprint of an email is estimated to range from <0.3g (for spam) to 4g (for regular email) and in 2019, roughly 55% of all email was spam. That amounts to about 215 million tonnes per year for email alone. Note, that does not take into account emails with large attachments which can have a carbon footprint of up to 50g each. It is worth remembering this the next time you consider a reply-to-all on an email with 50 recipients with a “thx” and a 5 MB embedded photo.

What about streaming?

A similar pattern can be found in other areas where we have adopted new technologies to move from physical to virtual solutions. Technology is perceived as the more environmentally friendly solution, but as the pattern and volume of consumption changes, the carbon footprint increases. For example, the trend is to move away from CDs, DVDs and Blu-rays towards audio and video streaming. Now, it is assumed that most music and video content should be available on demand 24/7. Where once television shows were watched once a week, this has been replaced with binge-watching entire series on video streaming services. For many office-based employees, streaming music throughout the day is routine. There are a lot of variables to consider, but one researcher has reported that streaming an album more than 27 times will use more energy than producing a physical copy.

And storing photos?

Most of us have that one treasured and faded photograph of a family member or a beloved pet. We have kept the physical copy safely in an old album for years. With the advent of the smartphone, we can now take dozens of near-identical digital photos of our children, pets (again) and in some cases, our dinners. These high-resolution masterpieces take up enormous storage space on digital devices, as well as the multiple backup copies in the cloud. This is an example of an energy cost invisible to the consumer.

How green is the cloud anyway?

All this cloud data needs to be saved somewhere. Most cloud services are hosted at vast datacentres spread around the globe. These are dominated by public cloud service providers, such as Google Cloud, Microsoft Azure and Amazon Web Services. Energy consumption by datacentres is an increasing challenge and is expected to double every four years. In fact, datacentres worldwide are forecasted to consume one third of all the energy in the ICT (information and communications technology) ecosystem by 2025.

Power Usage effectiveness – a little bit of maths

Because the cloud can only be as green as the energy it consumes, public cloud providers are under increasing pressure to build energy efficient datacentres which run entirely on renewable energy sources. The energy use of datacentres relates to the computer electricity consumption on one hand but also to maintaining the appropriate environment (temperature, security, etc.). For this they use the Power Usage Effectiveness (PUE) ratio. This metric compares energy used by the computing equipment with the total energy used by the datacentre, including all other devices (cooling, for example counts for about 30% of energy used by datacentres). One solution to this problem is to build datacentres in colder climates.


PUE = Total Facility Energy / IT Equipment Energy


An ideal PUE is 1.0 and at least one cloud provider has reported their datacentre PUE value as low as 1.11. In the past, most companies maintained their own servers in their offices which resulted in much higher PUE levels, equivalent to 2.50. Since then, many have adopted a hybrid approach by moving their equipment into datacentres (called colocations) and this has helped to some extent. A more efficient solution is to use the public cloud providers. The shift away from traditional on premises computer equipment to public cloud services should be welcomed. These cloud services operate on a scale where any small energy efficiency improvement or increased use of renewable energy sources can have a significant impact.

The power of small differences

In recent years, the number of homes without a computer, smartphone or tablet has become vanishingly small. Therefore, any changes to computing designs can have a huge impact on consumer energy consumption. For example, when default power settings are changed in Windows which make computers sleep more quickly or dim the display in the evening, this enables over a billion devices to consume a little less energy.

Consumer cloud services like YouTube can be similarly improved with small changes. Many people use YouTube as a (free) mobile music player, however, by default you are required to keep the app open (and the video playing) to listen. Transmitting, receiving and displaying the video stream consumes far more energy than the audio stream. Researchers have suggested that introducing a YouTube “radio mode” could save as much as 500,000 tonnes of Co2 per year, however, at present this feature is only available to premium subscribers.

Your own technology choices also play an important role here. The equipment lifecycle can be as important as the electricity use. Use your existing smartphone or computer longer before upgrading to the latest shiny new model. When it is time to replace that aging computer, be aware that desktops use on average 3 to 4 times more energy to run than laptop and about 10 times more than a tablet. You can also change the default settings in all your video streaming services by disabling the auto-play feature. And if you reduce the number of clips of skateboarding parrots you watch, this too will have a positive impact on your digital carbon footprint.

We have come a long way since alarmingly flammable copiers, but all this technological progress is now contributing a lot more to global warming than the odd office fire in the 1970s. The amount of Co2 you are saving by your valiant attempts to use reusable coffee cups is probably undermined every time you hit reply all and attach a video of that parrot to your company wide email. Dull as it sounds, moderating your use of technology is a big step in the right direction. Ultimately, taking time to switch (everything) off and disconnect from time to time might be the most valuable choice you can make.