Cutting Your Carbon Footprint

Tar Sands in Alberta (Image: Wikimedia/Howl Arts Collective)

Tar Sands in Alberta – the latest and dirtiest source of oil (Image: Wikimedia/Howl Arts Collective)

The effects of climate change are starting to be noticeable in many parts of the world, and the Intergovernmental Panel on Climate Change (IPCC) recently gave the strongest message yet on what the future holds for us and our children: “severe, pervasive and irreversible impacts for people and ecosystems”.

Many of us are naturally concerned about this and are looking to cut our carbon footprint. One of the most effective measures we can take to cut our transport footprint is to switch from a fossil-fuelled car to an electric car.

Calculating the carbon saved by switching to electric is complex and the subject of many ‘lifecycle analysis’ reports so it’s worth highlighting some rules of thumb:

  1. The carbon emitted in the manufacture of fossil-fuelled and electric cars is about the same (in some reports electric cars are slightly higher, but this will reduce over time as they are mass produced).
  2. Swapping from a fossil-fuelled to an electric car will roughly halve your carbon emissions from use if powered from the UK National Grid.
  3. A grid-powered electric car automatically reduces its emissions over time as the National Grid is decarbonising (largely through the replacement of coal power stations with renewables). Conventional cars tend to produce more emissions as they get older.
  4. If powered from renewable sources then your electric car produces no emissions from use. Options include using a renewable energy supplier (such as Ecotricity or Good Energy) and fitting solar panels – we will encourage you in this and can help with arranging both options.


Further Information

One important thing to remember if you want to compare emissions between an electric car and a fossil-fuelled one is that the official emissions figures quoted for a conventional car (e.g. “150g/km”) are only emissions from the car when travelling, and do not take into account what was emitted in the production and transport of the fuel.

In fact a lot of energy will have been expended – and hence emissions created – to extract, refine and transport this fuel before it even gets to the car. Figures vary on this, but beginning with 4.5kWh per gallon for the refining alone we can reasonably estimate 10kWh per gallon in total in the UK, or for the case of a petrol car that achieves 40mpg about 0.25kWh per mile. To drive 100 miles it will therefore use an additional 25kWh of electricity over and above the energy provided by the petrol.

A typical electric car has a 22 to 24kWh battery, so assuming some losses in charging we can say that it requires just 25kWh of electricity to go about 100 miles. This is because electric cars are much more efficient than combustion cars (only about a quarter of the energy in a gallon of petrol is used to drive the car, the rest is lost as heat).

What this means is:

An electric car can drive as far as a petrol car on just the energy wasted to get fuel into the petrol car

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