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How we calculate our carbon impact

By being with Bulb, you significantly shrink your carbon footprint. The average member lowers their carbon impact by 3.2 tonnes of CO2e a year.

How homes on Bulb lower their carbon impact by 3.2 tonnes of CO2e a year

To calculate this, we compare the carbon emissions you have for your energy use with Bulb, compared to what they’d be if you were with a typical supplier. In 2020, the average Bulb home used 4,491 kWh of electricity and 11,607 kWh of gas. We use these figures to make the comparison.

With Bulb, annual CO2 emissions for the energy you use at home are zero. This is because we provide 100% renewable electricity and 100% carbon neutral gas. So, homes with Bulb emit 0.00 kg of CO2 per kWh of electricity and 0.00 kg of CO2 per kWh of gas. 

With an average supplier, annual CO2 emissions for the energy you use at home would be around 3.2 tonnes per year. The UK government report on the carbon emissions for homes on the average energy fuel mix. In 2020, these figures were 0.233 kg of CO2e per kWh of electricity and 0.184kg of CO2e per kWh of gas. Over the course of a year, a Bulb home on the average UK fuel mix would emit 1.1 tonne of CO2e from electricity usage and 2.1 tonnes of CO2e from gas usage.

Making sense of this impact

3.2 tonnes of carbon is a lot. But it's hard to imagine. What does that much carbon look like? We like to put it in context to make things clearer. We might talk about 3.2 tonnes as a quarter of your total personal carbon emissions. Or we might compare this figure to something you’re more familiar with. For example, an Orca whale also weighs around 3.2 tonnes. 

According to a study by the Forestry Commission, it would take 1,590 trees to absorb that much carbon in a year. Kielder Forest’s 150 million trees lock up 82,000 tonnes of carbon every year. Each tree is locking up roughly 0.546 kg of carbon per year – equivalent to 2 kg of CO2. So, if one tree locks up 2 kg of CO2 per year, you'd need 1,590 trees to absorb 3.2 tonnes of it. 

We find that comparing your carbon impact to understandable things like animals and trees helps you to make sense of it. We’ll continue to explore new ways to do that.

Your impact has gone down (that's a good thing)

The impact you have on your carbon footprint by being with Bulb changes over time. In 2019, the average member reduced their footprint by 3.4 tonnes a year. In 2020, it’s 3.2 tonnes a year. This is because the amount of renewable electricity in the UK grid is increasing, along with the average energy usage of our members.

Every year, we review the average amount of energy used by a Bulb home, along with the government’s latest emissions factor for UK electricity. In 2020, the emissions factor decreased from 0.254 to 0.233 kg of CO2 per kWh because the grid is getting greener (hurray!). On top of that, our members are using less gas on average. That’s because quite a few homes only using electricity have joined. Together, this means the average member is having a smaller carbon impact in 2020 than they did in 2019. It’s great that things are moving in the right direction.