Deborah Chu

What’s the carbon footprint of an email?

2 min Read
Woman in a yellow shirt checking her phone

The average carbon footprint of an email is 0.3g CO2e. 

According to Mike Berners-Lee’s latest edition of How Bad Are Bananas, that’s the average emission for a short email that’s been sent from laptop to laptop. The numbers go down if it’s sent from phone to phone (0.2g CO2e), or if it’s a spam email that’s picked up by your inbox filter (0.03g CO2e).

The numbers go up, however, if it’s a long email that takes ten minutes to write and three seconds to read (17g CO2e), or if it’s got one image or an attachment (50g CO2e). The vast majority of these emissions come from the embodied carbon of the device it was sent on; smaller emissions come from the device’s electricity use, and the networks and data centres which send and store these emails. 

Over the course of a year, a person’s average email usage varies between 3 to 40kgs CO2e, which is the equivalent of driving between 10 to 128 miles in a small petrol car. So the individual contribution of our emails to global emissions might be small, but when magnified across the world’s 3.9 billion email users, that’s still quite a sizeable chunk of carbon. 

So, are emails a problem?

In the grand scheme of things, there’s definitely bigger fish to fry than our emails. But considering the pointlessness of a lot of it (cough: SPAM), this feels like a really easy win in terms of lowering your carbon footprint. So, before you hit ‘send’ on your two-word reply to Jurgen in HR, let’s look at the big picture:  

Currently, only 4.1 billion people, or 53.6% of the world’s population, has access to the internet (BBC). As access grows, it’s possible that the number of emails we send will grow too. This might result in a rise in the global carbon footprint of our emails. 

Speaking of crowded inboxes – emails are also an excellent example of the rebound effect, wherein a newer, more energy-efficient technology ends up consuming more energy, because our usage of this tech goes up. In How Bad Are Bananas, Berners-Lee estimates that the global population of email users sent 294 billion emails each day in 2019, and over half of that was spam (blech). So even though an email has 1/20th the footprint of its predecessor – the handwritten letter – most people are sending way more emails per day than they ever posted letters.

Wait, what exactly is a carbon footprint?

Don't worry - we break down what it means and how a carbon footprint is calculated in one handy article.
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Also, as Berners-Lee’s numbers-crunching has shown us, emails are one part of a much bigger equation that includes the embodied carbon of our gadgets and the systems that support them, i.e. the internet, data centres, etc. Digital technologies are currently responsible for 4% of the world’s total carbon emissions, and this figure is expected to double by 2025. Moreover, the amount of energy we’re consuming to manufacture and use our various gadgets and gizmos is rising by 9% a year (New Scientist).

So while emails themselves aren’t a massive problem at this current moment, they’re part of a larger digital system that’s growing rapidly, and thus producing more and more carbon. According to a report by the Financial Times, the data servers that house our emails now exceed the total carbon footprint of pre-Covid air travel. Most of these emissions come from the amount of energy these servers consume – and given that only 5% of the global power grid comes from renewable sources, that means most of our emails are powered by fossil fuels. 

What can we do about it?

First of all, it’s important to note that if an email can replace an in-person meeting that you’d have to travel for, definitely get typing. But if emailing is part of your day-to-day, there are plenty of ways to reduce its carbon footprint: 

  • Send less unnecessary emails. Obvious, yes. But did you know that emailing can actually be bad for your physical and mental health, as well as overall workplace productivity? Some conscious uncoupling might be necessary here. 
  • Copy less people into emails. Some people cc in their boss, their boss’ boss and their boss’ boss’ gran into emails as a means of ‘keeping everyone in the loop’. Why not streamline this process by sending just one round-up email at the end, containing only the need-to-know info? The higher-ups will appreciate you de-cluttering their inbox this way.
  • Send links to documents, rather than attaching them. This helps lessen the carbon load on your emails. 
  • Delete emails. A small gesture, yes, but this will reduce the amount of energy required to store them in data centres. Also it’s good for the soul to purge the junk folder once in a while. 
  • Unsubscribe from newsletters you don’t read. It’s not you, it’s me. But it’s actually, it’s also you. Toodle-doo. 


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