What’s the Carbon Footprint of Your Email?

Earth Day has many thinking about how to reduce waste in our daily lives. Searching for ways to lower personal greenhouse gas emissions is a good start, but one subtle source of CO2 is staring you right in the face. For many, the place bursting with waste isn’t a bin or closet—it’s their email inbox.

In the time it’s taken you to read this, there’s a good chance that the spam folder of your inbox just received another useless email. Maybe it’s in your work inbox, or your personal inbox, or your other personal inbox, or your other other personal inbox, but that email is taking up digital space—and the electricity required to do so—all the same.

And while spam may be the most annoying perpetrator of unwanted waste in your email, the messages we actually compose and read ourselves add more to our carbon footprint than you may realize. SEDNA is on a mission to stop email overload, and have put together below the numbers behind excessive email culture, as well as some simple ways improving your email habits can benefit the planet as a whole.

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How Do You Calculate the Carbon Footprint of an Email?

Understanding the environmental impact of an email starts with figuring out how to measure the greenhouse gas emissions created by one. When composing a message, your laptop or phone is using electricity. When you hit “Send” on the message, the network connection powering your Internet uses electricity, as does the server that transfers your message to its intended recipient. So, how do we measure the total carbon footprint of an email?

That’s what Lancaster University professor Michael Berners-Lee set out to quantify in his 2010 book “How Bad Are Bananas?” Using the metric CO2e (which represents the combined carbon dioxide equivalents from all forms of greenhouse gas the source generates), Berners-Lee calculates an estimated measure of the carbon contribution of everyday products and routine activities, including email use.

As a yardstick, Berners-Lee averages each person’s annual individual carbon footprint as being about 7 tonnes CO2e. To give you an idea of what that looks like, know that you would release one tonne of carbon by burning about 120 gallons of gasoline; that’s enough petrol to fill a living room aquarium.

Most people don’t think in fish tanks though, so translating CO2e sometimes takes more relatable comparisons. In late 2019, you may have seen headlines claiming staggering stats about the waste of “Thank You” emails alone—those one-to-two-word messages of gratitude that, unfortunately, still cause carbon. Energy supply company OVO caused a minor stir when estimating that each round of Thank You emails made by the adult population of the U.K. alone created the carbon equivalent of 81,152 flights from Heathrow to Madrid—that’s a lot of fish tanks!

But just as our understanding of the impact of emissions continues to evolve, so too do our methods of measuring that impact. That’s why Berners-Lee updated his findings last year with updated data. The result: a more accurate understanding of what our email footprint really looks like.

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What Is the Carbon Footprint of Email?

With new data in hand, Berners-Lee estimates that an individual email can be anywhere from from 0.03g CO2e  to 26g CO2e. That wide range owes to the different ways in which emails are used, both by those with good intentions and those without.

When it comes to the latter, spam is the most benign offender, coming in at only 0.03g CO2e. But what about the sheer volume of spam being sent, which is exactly what makes it so annoying in the first place? Statista estimated more than 306 billion emails were sent by email users in 2020, with just under 50% of those being spam messages. If that balance shocks you, it’s probably because your inbox spam filters are doing their job, preventing unwanted spam from ever getting your attention. These unseen messages still use electricity as they travel, but spam only accounts for a negligible percentage of your inbox’s carbon footprint.

The reason? As it turns out, attention paid to each individual email is just as, if not more important than, the volume of email sent itself. That’s because the longer you spend composing, reading, or replying to a message, the more electricity you’re using. Even a short email that’s written and read efficiently produces 0.3g CO2e, 10 times the amount of a spam message.

Where the numbers really start ballooning are in mass-blast, long-winded, “this email could have been a text*” messages. Berners-Lee saves such examples for the upper range of his estimates, calculating that an email you spend 10 minutes writing, then send to 1 person who actually reads it, as well as 99 other people who scan and ignore the message, creates 26g CO2e. With 4 billion email users active globally, that 26g can add up quickly.

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So, Is My Inbox Killing the Planet?

The (mostly) good news is, no. By Berners-Lee’s accounting, even if every email sent required 4 minutes of combined reading and writing time, the total amount of carbon created annually would be 150 million tonnes globally, accounting for 0.3% of the world’s footprint. It’s a drop in the bucket compared to other contributors, and as an alternative to letter mail (which creates 20 times as much CO2e), email is generally an efficient means of sending written communications.

But like any new technology, increased efficiency runs the risk of creating more carbon through excessive, careless use. Even if the small but real contribution your inbox makes to your personal emission count doesn’t give you pause, the other waste created by an unmanageable inbox—lost time, wasted storage, annoying notifications— may. For your own sake, as well as the planet’s, consider adopting some of these useful tactics for improving your email hygiene:

  • Unsubscribe from mailing lists you don’t use

  • Keep your own mailing lists up-to-date

  • Write concisely

  • Only message those who need the information you’re sending

  • Avoid sharing your email address with potential sources of spam

Unfortunately, there’s no silver bullet for greenhouse gases the way there is for reducing email volume. But like other environmentally-conscious changes of habit, whether that’s choosing to bike somewhere instead of driving, or making dietary adjustments, the associated benefits of lowering your carbon contributions can be reason enough to make a change. After all, who wouldn’t be happier in a world with lower emissions, as well as fewer emails?

Want to reduce your own organization’s email volume as much as 95%? Book a free, personalized demo of SEDNA to see how.


*0.8 g CO2e for a single text message, according to “How Bad are Bananas?” 2020