Update 23/01/2020: It’s been brought to our attention that these figures are now out of date. We’ve gone back to our expert to get a new answer – watch this space.
Less energy than letters
Every email we send uses electricity to display it, and the network connection uses electricity while the email is being transferred. As the email travels across the internet, each server will use some electricity to temporarily store it, before passing it on. Still, sending an email only uses about 1.7 per cent of the energy of delivering a paper letter – but we do send more emails!
For a typical email, this electricity is responsible for 4g of CO2 emissions. If it has a picture attachment, this needs extra storage and takes longer to transmit, so the carbon footprint rises to an average of 50g. Spam emails are mostly deleted automatically by the email servers before you see them so they don’t travel as far and only produce 0.3g each.
Compare to your car
Sending 65 emails is roughly equivalent to driving 1km in a car. In a year, an average person in the developed world adds 136kg of CO2 to their carbon footprint from the emails they send and receive. This is equivalent to an extra 320km driven in a car. Globally, the world’s email usage generates as much CO2 as having an extra seven million cars on the roads.