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Cutting carbon

We’ve worked out the carbon footprint of our emails

A few days ago, one of our members asked us about the carbon impact of sending fancy emails with large images and PDFs attached. We think it’s really important that any business can measure their full CO2 impact, so we love getting questions like this. But the maths is a little more complicated than you might think. We thought it might be helpful to dig into the numbers behind our colourful emails (and why we think they’re still worth sending).

Working out the carbon impact of emails is tricky (but we've done it)

The internet uses around 10% of the world’s energy demand, and produces around 2% of global emissions. That’s the same as the emissions produced by the aviation industry. At Bulb, we measure the carbon impact of all our business activities and report on them every year, including the CO2 created by sending our members emails. 

To work out how much CO2 is created by our emails, we need to calculate how much energy is used first. This can be complicated because there are two sides to every email - us hitting ‘send’ and our members hitting ‘open’. So there is lots to consider, like which device you use to read your emails, or if you charge that device with renewable power. And at our end, things like the transmission of email data to data centres across miles of fibre optic cables, or the amount of energy needed once it gets there. 

Data centres are essentially large warehouses for computer servers that control global internet traffic. They need enormous amounts of energy because they can never be turned off, which means they get very hot. So, they need plenty of cooling equipment to stop them overheating. 

Data centres are essentially large warehouses for computer servers

Luckily, some clever scientists have worked out that 1 gigabyte of data requires around 3-7 kWh of energy to be stored in the cloud. At Bulb, we send our emails through cloud-based servers. So, we can use this number to estimate how much energy we use to send our emails. 

We send each Bulb member around 3 emails a month. That means we send about 5 million emails altogether, every month. We send statements with a PDF attached, and our other emails usually have one or two large (but pretty) images. An email with an image or PDF attached is about 1 megabyte. So that works out to be 25,000 kWh of energy to send those emails each month.

At Bulb, we send most of our emails through Google Cloud Platform, which runs on 100% renewable energy. This means the emissions from sending these emails is zero.

Where we can’t use servers powered by renewables, we send our emails through other platforms with data centres in America. To calculate these emissions, we take into account the emissions produced by generating electricity in the US. So, the carbon impact of sending Bulb emails (or, 5 million 1MB emails a month) is 63 tonnes of CO2 a year. We’re a carbon neutral company, which means we offset all of our emissions. That includes CO2 created by sending emails. 

Using pictures in our emails means more members engage with energy

The average PDF or image we send is 500KB. If we removed all those images, we’d save around 32 tonnes of CO2 a year. This is a saving, clearly. In fact, it’s roughly the same as 3 people’s yearly carbon footprint. But we think that carbon impact has to be balanced with the role images play in convincing people to switch to (and stay with) a renewable energy supplier. They can make the world of energy more engaging and easier to understand – and they can add some joy. That’s valuable, too. 

We want people to pay attention to their energy - where they get it from and how they use it. To help, we try to send emails that are simple and, dare we say it, delightful. That way, our members are more likely to open the email, submit that meter reading or think about the best time of day to use energy.

Illustrations make emails more fun and engaging, which can help people stay with renewable suppliers

That’s the good thing about renewable energy: if your power comes from the sun or the wind you can spend those good electrons on pleasure and fun. And remember, being with a renewable supplier like Bulb can shrink your carbon footprint by 3.2 tonnes of CO2 a year

We're exploring ways to lower this impact

That being said, we’re always trying to do better. So our engineers are looking at ways we can reduce the size of the images and PDFs we send to our members, too. If we reduce that, we’ll need less energy to send them, and we can bring our carbon impact down even further. In the meantime, we’ll continue to make sure as many of our servers as possible are with companies supplied by renewables. And we’ll offset the emissions that we can’t prevent to bring our impact back to zero.