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The Carbon Cost of an Email

February 2018 by Emma Richards

Image credit: Photo by Miguel Á. Padriñán

Update: 19/11/20

‘How Bad are Bananas?: The Carbon Footprint of Everything’ by Mike Berners-Lee, was published in 2010 and the figures included in this article, written in 2018, reflect this. ‘How Bad are Bananas?’ has since been re-released on the 03/09/2020 with updated figures taking into account new learning and understanding of the attribution of emissions, as well as changes come about through the ongoing decarbonisation of the energy sector, among others. For the latest figures please refer to the new version of the book. You can read Mike Berners-Lee’s tweet on the topic here, and a BBC article looking at the issue of using out of date facts and figures, such as these, in policymaking and action planning. The original blog, as written in 2018, is below; as such please do not use these figures as the basis of any calculations.


Original Blog

It is likely that you have sent or received one email so far today, or even 10 or more! When writing, sending or receiving emails the last thing you’re probably thinking about is the carbon footprint – but should you be?

After all, once an email has been sent it’s out there forever, somewhere…

Carbon Literacy is ‘an awareness of the carbon dioxide costs and impacts of everyday activities, and the ability and motivation to reduce emissions on an individual, community, and organisational basis’.

So it’s no surprise that once Carbon Literate, it becomes apparent that everything and every aspect of life has a carbon footprint – no matter how small or seemingly insignificant. This includes the email you just sent.

Below are the average carbon footprints of different emails:

An average spam email:  0.3 g CO2e (carbon dioxide equivalent)

A standard email: 4 g CO2e

An email with “long and tiresome attachments”: 50 g CO2e

This information is taken from the book by Mike Berners-Lee: ‘How Bad are Bananas?: The Carbon Footprint of Everything’ (2010). Mike Burners-Lee is the brother of Tim Burners-Lee, (the guy who invented the world wide web) two pretty smart guys if you ask me.

This might not initially seem like a lot, but when you consider the number of emails sent and received, it’s easy to see how this can add up. Let’s take a look –

It is estimated that the average office worker receives 121 emails per day, and that half of these will be spam (Global News). Based on my own emails, the remaining half is almost equally comprised of those with and without attachments (those with attachments predominantly have more than one). So…

60.5 spam emails  x   0.3 g CO2e  =  18.5 g CO2e
30.25 standard emails  x  4 g CO2e  =  121 g CO2e
30.25 emails with attachments  x  50 g CO2e  =  1512.5 g CO2e

This means that a day’s worth of emails received is equal to  1,652 g CO2e

And that one year’s worth of emails received equals  603,393 g CO2e  = 0.593863329 or 0.6 tonnes CO2e

To put this into perspective, the total yearly carbon footprint of the average person living in India is approx 1.5 tonnes CO2e(Climate Outreach).

By this account, it takes just three average office workers’ yearly received emails to surpass that of another human’s carbon footprint for all their activity for a whole year.

I bet your emails don’t seem quite so insignificant now?

Given the scale of what before seemed a minor impact on climate change, it is encouraging to learn that “ICT solutions have the potential to enable a reduction in global greenhouse gas emissions of up to 15.3% by 2030″ (Policy Connect).  But what can you do as an individual?

1. Reduce the size of emails by lowering the resolution and compressing images and avoid large HTML elements.

2. Regularly clean and maintain mailing lists.

3. Remove any contacts that unsubscribe, and update changed email address immediately.

4. Check your emails thoroughly before sending to ensure they contain all the necessary (and correct) information, to avoid the need for a follow-up email.

5. Link to files or information online rather than adding an attachment.


It is important that we take action on the climate crisis where we can, and although reducing the carbon footprint of your emails is a part of the solution, it’s also important to be aware that, in most cases, it’s unlikely to make a significant impact to reduce your carbon footprint. There are, however, lots of easy wins – simple actions which will reduce your carbon footprint in a significant way – that you can also look to take. You can find out more about the need for action which has a high carbon reduction impact here.


Some of the advice listed above has been adapted from Mail Jet.

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