Nissan Leaf - Hidden Emissions

Monday 22nd March, 2010
After reading this piece, please see my updated "One Year Later" article.

Following the Nissan Leaf running cost article I wrote last week, I've had a number of people asking about its Green credentials and what kind of carbon footprint it might create for a potential owner. I thought I may as well get my calculator out and do some more sums.

Just to clarify, the Nissan Leaf doesn't have a combustion engine. It doesn't have an exhaust pipe. It's just a milk float style vehicle that is charged from the owner's electricity supply. So driving the car creates no direct emissions and it's CO2 output could be considered as nil, but not if that electricity is sourced using fossil fuels.

If, like me, you're based in the UK; you'll find that the majority of your electricity comes from traditional Coal fired power stations. We do have a bit of nuclear and a bit of wind power but, overall, most of it is generated using steam turbines powered by burning coal and emitting CO2. For this reason, many people have been buying electricity saving devices for the home. For example,  Bye Bye Standby allows you to quickly and easily turn off the power to appliances in your home remotely. This reduces your electricity bills and helps save the millions of kWh of electricity wasted each year by appliances left on stand-by unnecessarily. The same electricity you were trying to save will be used to power your electric car.

@NeilatNissanEU tells me "using electricity to power cars remains vastly less polluting than petrol" but is this the case for owners of the Nissan Leaf in the UK? For "normal" cars, taxation is usually calculated using CO2 output figures. This applies to both VED and company car BIK calculations. Drivers of a hybrid, like me, have discovered that driving a low emission hybrid vehicle can save the owner a lot of money in this area as a result. The Nissan Leaf, being electric, is regarded as not having a CO2 output, exempt from London congestion charges and, presumably, will have zero car tax. But what if we factored in that CO2 output from electricity generation? Well, let's do the maths.

I'll be using figures from the National Energy Foundation (NEF) who have a rather handy CO2 calculator on their site. Using this, and the numbers from the running cost article, we will easily be able to create an equivalent figure for grammes per km CO2. This may allow green drivers to make a more informed decision before buying their next vehicle.

As you likely already know, the Nissan Leaf battery pack stores 24kWh of electricity which provides a max range of about 100 miles. According to the NEF calculator, generating 24kWh of electricity in the UK creates approximately 13kg of CO2 emissions. So, with a bit of simple maths, that's 13,000g for 100miles or 130g per mile of CO2. There are 1.6km in a mile so 130/1.6 = 81.25g per km CO2.

So 81.25g of CO2 per km for a Nissan Leaf on a warm sunny day that doesn't require the air conditioning. Don't get me wrong, this is still very low emissions, and fully establishes the Leaf's green credentials but, if electricity usage increases by just 10%, due to the heater, air-con, headlights, radio, going uphill etc. then it's CO2 output will be no better than the physically larger 89-92g/km Toyota Prius and it's 800+ miles range. It's certainly not "vastly less polluting" in my eyes.

As with the running cost calculations I did last week, I personally think that the Leaf may be too big a compromise for too small a gain. Sure, when we switch to more renewable sources of electricity and our power supply generation becomes greener, then things will be different - but I see this as being over a decade away. The government were recently giving people cash incentives to scrap 10 year old cars so, using that as the lifetime of a car, I don't see the current generation Leaf ever being a viable option for me.

Next time you see a website claiming "zero emission" think again.

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