Mail’s carbon footprint: How much CO₂ does an email produce?

In this article, you can learn how much CO₂ each type of mail produces and the ecological impact associated with it. Can you save the climate by cleaning up your inbox? Let’s find out!

Why do emails produce CO₂?

Sending messages to your colleagues, friends and family is easy. All it takes is one click. But this requires electricity. This electricity is often sourced from fossil fuels. As a result, a substantial carbon footprint is created. Every email we send or receive contributes to the emission of greenhouse gases. CO₂ emissions associated with emails are primarily caused by the technological devices we use to transport a message from the sender to the recipient.

How do email services consume energy?

Email services are designed to transmit and store messages securely. This means that servers need a lot of energy to ensure constant availability and reliable performance. It would be a shame if you’d only sometimes be able to check your inbox.

This means that servers are operating around the clock to process, store and transmit emails. These servers are hosted in large data centres that are equipped with cooling systems to protect the hardware from overheating. Maintaining the ideal temperature for continuous operation requires significant amounts of electrical energy.

The energy consumed by servers and data centres is often supplied by non-renewable energy sources that cause the emission of greenhouse gases such as CO₂. This use of energy leaves a significant carbon footprint that is directly linked to our digital communication. The ever-increasing use of email services, the growing volume of stored emails and the rising demand for real-time communication are contributing to a further increase in energy consumption and CO₂ emissions.

Which factors play a role in an email’s carbon footprint?

Understanding the complex relationship between email and CO₂ emissions is important so that we can use our digital communication technologies more responsibly. In the following sections, we will take a closer look at energy consumption and strategies to reduce the carbon footprint of emails with the goal of promoting more sustainable digital communication practices.

The running of servers and data centres

One of the key factors is the operation of servers and data centres, which act as the heart of the digital communication network. These servers require a continuous supply of energy to store, process and transmit emails. The energy consumption of this infrastructure is often covered by non-renewable resources such as coal or natural gas, resulting in significant CO₂ emissions.

Sending and storing data

Other factors include the traffic generated by the transmission of emails as well as the additional resources required for spam filters, backups and attachments. Global growth in email usage and the rising tendency to send large files as attachments also contribute to the increasing ecological footprint of emails.

How much CO₂ does mail produce?

Here you can see how common forms of communication compare in terms of their CO₂ emissions:

Form of communication	How much CO2 per message?
Letter	20 grams
Spam email without reading	0.03 grams
Short email via phone	0.2 grams
Short email via laptop	0.3 grams
Long email	17 grams

Sources: Carbon Literacy Project, Transport Friendly Society

A carbon footprint comparison: email vs. letter

There’s no question that an email requires fewer resources than a letter. This is clear from the table above. Companies can therefore reduce their CO₂ emissions and be more environmentally friendly by avoiding the use of paper.

A letter produces 20 grams of CO₂. For the same amount of CO₂, you can send around 67 short emails. That makes a huge difference. In Germany alone, 40 million letters are sent every day.

How much CO₂ does global data traffic produce?

We are all aware that air travel is a major producer of greenhouse gases and accounts for around 3 per cent of global CO₂ emissions. The internet is often overlooked in these debates.

However, the carbon footprint of the internet is larger than that of air traffic. Experts estimate that the internet accounts for between 2 and 4 per cent of global CO₂ emissions.

Worldwide, we send 300 billion emails every day. If an email produces 0.2 grams of CO₂ at best (short email), that’s 600,000 kilograms of CO₂ per day. This means that over 2 million tonnes of CO₂ are emitted by email communications every year - and this figure is rising rapidly.

What you can do to reduce your carbon footprint when sending emails

Reducing the carbon footprint of emails does not require radical changes, but rather more awareness of digital communication habits. Here are some tips on how individuals can reduce their environmental impact when sending emails:

Limit email attachments and file sizes: The larger a file sent via email, the more traffic and energy it requires. If possible, use alternative methods such as cloud storage or file sharing services to share large files instead of sending them as attachments.

Delete unused emails and attachments: Regularly sort out your emails and delete those that are no longer needed. This not only helps you keep your inbox organised, but also reduces the storage requirements on the servers. Less stored data ultimately means less energy consumption and CO₂ emissions.

Use eco-friendly email providers: Some email providers rely on renewable energy and energy-efficient technologies to reduce their carbon footprint. By using such a provider, you can help to minimise the environmental impact of your email usage.

Only save your emails locally Your email program can save messags locally on your computer instead of on the server. If, for instance, you’d move all mails older than two years from the server to a local folder, you can balance availability of mails on your other devices and server storage use.

Sustainable email signatures: Shorten your email signature to minimise space requirements. Remove any images and logos, because these usually contain more data than the email text itself. This reduces the size of each email and therefore the energy consumption during transmission.

Mindful use of email newsletters: Only subscribe to email newsletters that you actually want to read. This not only avoids energy consumption, but also reduces the amount of data traffic.

How useful is it to reduce the carbon footprint of your emails?

By integrating these approaches into our email routine, we can collectively help to reduce the carbon footprint of digital communication and contribute to sustainability. At the same time, the efforts of email providers to increase efficiency and operate in a more environmentally friendly way are also a promising step in the right direction.

Can you protect the climate by cleaning up your inbox?

Before you spend a lot of time cleaning up your inbox, it is important to know that the majority of email traffic is business-related. Marketing and IT companies in particular, as well as email service providers, have much more leverage here - and therefore more responsibility.

Of course, we don’t want to discourage you from cleaning up your emails. But for your personal climate impact, there certainly are areas where you can achieve more with less effort. Here’s how the carbon emissions caused by sending an e-mail compares to other activities:

Activity	CO2 emissions
Send an email	Less than 1 gram
Ask ChatGPT a question	2–3 grams
Watch Netflix	36–55 grams/hour
Join a video call	150–1 000 grams/hour
Heat your home	400–4 563 grams/hour*
Drive a car	17 700 grams/100 km

*) Here we used data from the German Federal Environment Agency for 50 m² apartments in energy-efficient buildings to badly insulated 300 m² houses. We assumed 190 days annual heating days on which the heater is on for 16 hours.

Note that the numbers in the table above are rough estimations, where just like with sending an e-mail, many factors can affect the real emissions.