Every email you send and receive emits carbon. How much depends on many different factors, including:
- the age of your phone or laptop
- how long it takes to write and read the email
- whether there were any images or attachments
- how much energy it took to send and pass it through various data centres.
The carbon cost of an email
It’s tricky to calculate the carbon footprint of an email because there are so many variables. These figures are the best guess by various trusted sources.
One email has roughly the same carbon footprint as a lightbulb turned on for six minutes.
A staggering 251,100,000 emails are sent every single minute. On average, a typical office worker is responsible for about 135 kg of CO2 per year just by sending emails.
Even short emails add up. If every adult in the UK sent one less “thank you” email, it could save more than 16,000 tonnes of carbon a year – the equivalent to taking 3,334 diesel cars off the road or 81,1522 flights to Madrid.
| Email type | Emissions (Co2e) |
|---|---|
| Spam email picked up by your filters | 0.03 g |
| Short email sent and received on a phone | 0.2 g |
| Short email sent and received on a laptop | 0.3 g |
| Long email that takes 10 minutes to write and 3 minutes to read, sent and delivered on a laptop | 17 g |
| Email blast that takes 10 minutes to write and sent to 100 people, of whom 1 reads it and the other 99 glance at it for 3 seconds to decide that they should ignore it | 26 g |
| Email with a large attachment | 50 g |
Junk mail?
An email newsletter generates around 10 grams of CO2, and 90% are never opened!
Thirty-two billion trees would have to be planted every year to offset the pollution caused by unopened attachments, unread email and spam. [Source: Gerry McGovern, Digital is Physical]
Many email platforms recommend that companies send extra emails around Black Friday. An estimated 86.7 billion extra emails are sent to promote Black Friday deals.
A drop in the ocean
It’s true that when we look at the bigger picture, the carbon footprint of one person’s emails is just a drop in the ocean. But as Mike Berners-Lee pointed out, cutting waste from your inbox is part of creating the right mindset to demand change:
“Whilst the carbon footprint of an email isn’t huge, it’s a great illustration of the broader principle that cutting the waste out of our lives is good for our wellbeing and good for the environment.
“Every time we take a small step towards changing our behaviour, be that sending fewer emails or carrying a reusable coffee cup, we need to treat it as a reminder to ourselves and others that we care even more about the really big carbon decisions.”
[Source: Mike Berners-Lee & Ovo Energy]
Unread, spam and unnecessary emails emit carbon and contribute to digital waste. So, it’s good practice to manage your inbox and monitor your email habits.
How you can help
- Only send an email if you have to
- Review the company culture surrounding emails: e.g. suggest people don’t send quick messages such as “thank you!”
- Use alternative messaging tools such as WhatsApp, which consume less energy (see the messaging section below)
- Follow these simple steps to clean up your inbox and measure the impact
- Review your recipients – does everyone really need to be copied in?
- Take steps to avoid email shots going straight into Junk: ensure your email template is set up correctly and test before you send to all
- Reduce the file size and compress any images or attachments before you send them
- Don’t send large files on email. Use WeTransfer, Google Drive or OneDrive instead
- Spellcheck, proofread and check for broken links before you hit send. Poor content is bound to generate unnecessary responses (more carbon!) and then you’ll have to edit and resend the message. This causes twice the harm to the planet
- Only include your email signature in new emails – switch it off for replies
- Start counting emails as part of your carbon-generating activity, and include the data in your sustainability reporting – especially if you send emails to large audiences
- Switch to a greener email marketing platform like EcoSend.
Message mindfully
Not all messaging apps are equal when it comes to energy consumption and carbon emissions.
The application with the best carbon impact is WhatsApp, which compresses image and GIF files. This emits 44% less carbon than Slack. 1,040,000 messages were sent on Slack every minute in 2024.
Other messaging apps have sustainability at their core. Try Treebal, an instant messaging tool that has 15 times less impact than an email and supports reforestation projects.
How you can help
- Use Treebal or WhatsApp as your default messaging app
- Don’t send GIFs, PDFs and other files over messaging apps – send links to stored files instead.