What‘s the carbon footprint of an email?

Nowadays we are all asking ourselves “How can I reduce my carbon footprint?” And many of us are spending more and more time online – working remotely as well as streaming our favorite series and listening to music. In many cases business travel has also been replaced by chats, video calls, and, of course, emails. Each of these online activities still cause carbon emissions, even if it's only a few grams.
Windfarm with four wind turbines
Email’s carbon footprint depends on the energy used in the data center

This is because energy needs to be generated to power our devices and Wi-Fi – and, more significantly, the data centers and servers needed to store all that content and keep the internet running. So how do our emailing habits impact the environment?

  1. Email carbon footprint: calculations vary
  2. Data centers and our carbon footprint
  3. mail.com and green energy
  4. Reduce your email carbon footprint
  5. Email vs. text vs. snail mail

What is the footprint of email?

On average, the carbon footprint of an email is 0.3g CO2e; however, the footprint of an individual email can vary dramatically. In 2020,  Mike Berners-Lee, a researcher at Lancaster University (and brother of the man who invented the World Wide Web!), crunched some numbers and came up with figures ranging from 0.03 g CO2e (carbon dioxide equivalent) for a spam email that is picked up by filters and never delivered to 26g CO2e for a marketing email that is only read by 1 of 100 recipients.  These numbers not only account for the IT infrastructure needed to receive, read, write and send emails in your home or office, but also the power used by the servers and data centers that process and store them. Based on these figures, he estimated that the average person’s email use in a year has a carbon footprint similar to driving a small, gasoline-powered car almost 130 miles.

The good news from Berners-Lee’s analysis: In 2010 he estimated the carbon footprint of an email with a “long and tiresome attachment” at 30g CO2e, but the top figure in his 2020 figures was 4g CO2 e less. One reason for this drop is that devices and servers are becoming more energy efficient.

A study performed in 2019 by the UK power company Ovo Energy tackled the problem from the other end, calculating how much we can reduce our carbon footprint by cutting down on emailing. Their conclusion: if every email user in that country were to send one fewer email per day, it would lead to a total annual reduction of 16,433 metric tons CO2e – the equivalent of 81,152 flights between London Heathrow and Madrid.
Pro tip: Email mindfulness

Ovo Energy has suggested not sending unnecessary brief replies like “Thank you” or “OK” (even if that goes against the grain of the British email culture). To help users be more mindful of their email habits, they have even introduced a Chrome extension that looks at the word count of your email and invites you to reflect on whether you actually need to send an email of under four words.

Data centers and your digital carbon footprint

The two factors contributing to our email carbon footprint are the energy used at home or work to write the emails, and the energy it takes to store and transmit them through servers and data centers. The energy efficiency of data centers has been improving by leaps and bounds, but in the United States they are still responsible for two percent of the country’s electricity use. Everywhere you look nowadays, however, electricity is being generated by cleaner methods, which means that the energy powering servers and data centers is greener as well.

Climate-friendly email from mail.com

In the case of mail.com, our data center in Kansas – which has an annual power consumption of 13 GWh – has been using wind energy since 2020. We also do carbon offsets for the footprint of our headquarters in Pennsylvania in the form of renewable energy certificates. So we can proudly affirm that mail.com is an extremely climate-friendly email service. This helps all mail.com users shrink their personal carbon footprint through the reduced environmental impact of sending or receiving email.

How you can reduce your email carbon footprint at home

Besides signing up with a green email provider, there are other steps individuals can take to bring the climate impact of each email down to zero. The most important is choosing the right home energy supplier to make sure your email inbox across screens is being powered by green energy. In addition, environmental experts suggest reducing the size of emails and the amount of email data you save to cut the amount of power it takes to store them. Here are a few tricks that can help:
  • Send links to files instead of attachments (our free Cloud file sharing feature is great for this!)
  • Unsubscribe from newsletters you no longer read
  • Reduce email size by compressing images and avoiding large HTML elements
  • Regularly update your mailing lists so no messages are sent to invalid addresses
  • Delete old, unnecessary emails from your custom folders, and empty your Trash and Spam folders regularly (check your folder settings)
  • Turn off social media email notifications – usually they just duplicate information you already see online
You may be thinking that some of these points look familiar – indeed, several of these tricks are also effective in reducing the amount of spam you see in your inbox. A real win-win situation!

Carbon footprint of email vs. text or letter

You may also have wondered what the most climate-friendly way to keep in touch is – if a text message or a good old-fashioned letter might have a lower carbon footprint than your email. In a 2016 interview, Berners-Lee estimated that a regular text message is only about 0.014g CO2e, which is only a tiny fraction of the average person’s daily carbon footprint of 30 kg per day – about 700 times less than the average email. These calculations vary extensively, however, with French IT expert Frederic Bordage putting the number much lower at 0.00215 g. It is clear, however, that a text has a lower carbon footprint than an email. Snail mail, on the other hand, has a much larger environmental impact: A 10-gram letter averages 140g CO2e, or 14 times more than an email.This larger number makes sense, since it includes the carbon emissions of the vehicles used to transport the letter from sender to recipient.
How do you calculate carbon footprint of email?

The calculation of your individual email carbon footprint can be complicated, since it requires you to factor in the amount of time you spend writing and sending emails, the number of messages, and what sort of electricity used in your home or office as well as in the email data center. However, if you’d like to an estimate of what your personal email carbon footprint is, check out the email carbon footprint calculator from 8 Billion Trees.

If you’d like to learn more about mail.com and United Internet’s commitment to green energy, please see our 2022 Sustainability Report. And if you still don’t have a climate-friendly email account with mail.com, you can sign up for free here.

This article first appeared on April 22, 2021 and was updated on June 12, 2023

Images: 1&1/Getty Images

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