In the search for ways to reduce our carbon footprint and overall burden on the environment, cars are a really big deal. With new all-electric cars on the market, many consumers have assumed that buying one of these new, high tech battery-powered cars is a green decision. It is. There are, however, complex and subtle issues worth considering, particularly if a new EV or Hybrid is out of price range.
Let’s compare two cars that represent different environmental impacts. On the one hand, the new completely electric Nissan Leaf which eschews gasoline for plugging in to the local power grid. On the other hand, we have a carefully used and fuel efficient 2003 Nissan Sentra.
The 03′ Nissan Sentra
A reasonably high-quality compact that was once known for being incredibly fuel efficient, the used 2003 Sentra of today is nearly 10 years old. While dependable, our example car has more than 100k miles and currently averages about 28 mpg during a mostly highway commute.
Calculating the environmental impact of this old car boils down to assessing the monthly carbon footprint as well as considering the carbon footprint of maintenance. The environmental impact of building this car is long over, so we won’t take that into consideration.
Used 2003 Nissan Sentra Carbon Footprint
- 1000 miles of monthly use / 28mpg = 35.7 gallons of gasoline
- 35.7 gallons * 20.35 lbs of CO2 per gallon = 727 lbs of CO2 per month
- Oil changes and other misc. oil use = 100lbs of CO2 per month (est.)
- Total: 827lbs of CO2 per month, give or take
The New Nissan Leaf
The Leaf is 100% all-electric – there is no internal combustion engine, so the Leaf does not burn any gas. However, the vehicle is plugged into the commercial electrical grid and power plants that feed the electrical grid use carbon-based fuel sources. If we assume that the Leaf gets 3.5 miles per kW-hr and that the driver plugs into an “average” fuel grid, then 1kW-hr of electricity generates about 1.4 lbs of CO2 (the national average). Using these two numbers, we can calculate the carbon footprint of this monthly electricity use.
New 2013 Nissan Leaf Carbon Footprint
- 1000 miles of monthly use / 3.5 miles per kW-hr = 288 kW-hrs of electricity
- 288 kW-hr * 1.4 lbs of CO2 per = 403 lbs of CO2 per month
- Total: 403lbs of CO2 per month
Additionally, we’ve got to account for the carbon impact of buying a brand new vehicle. The Leaf produces about 8.25 tons of carbon during assembly according to the UK’s Low Carbon Vehicle Partnership (see GreenCarCongress.com). That one-time carbon “cost” must be accounted for on a monthly basis. If we assume that the leaf will have an 8 year, 150k mile lifetime (and that may be a very generous assumption, as the battery pack is likely to fail before that time), then our monthly CO2 estimate must include an additional 171 lbs of CO2 for assembly. This gives us a net monthly number around 575lbs of CO2 used per month.
So Which is Better?
In the long-run, the Nissan Leaf is clearly the more environmentally friendly choice. Over the course of a decade or so, driving the Leaf will net out to a lower carbon footprint. However, for those who cannot afford a new EV or make other choices the comparison is not as bad as one might expect.
As always, there are some mitigating factors:
- Some states aren’t as carbon-efficient when it comes to generating electricity. If the energy grid in your state generates more than 2.28 lbs of CO2 per kW-hr, the electric Leaf is no better than the gas-powered Sentra
- There’s nothing stopping a Sentra owner from using some or all of the money saved buying a used car to purchase some carbon offset credits. The price difference between a used 2003 Sentra and a new Leaf is substantial ($20k or so) – that can buy a lot of carbon offsets.
- There are other benefits to driving a new Leaf to consider. Improved safety, comfort, ride, handling – while none of these factors benefit the environment, they DO change the “math” for the average consumer.
- Solar charging changes the comparison massively in favor of the EV.
Whatever you decide, it’s important to look at the entire life-cycle of your purchase. In many ways, buying and maintaining an older vehicle – and using some of the money you save to buy credits – might be the most environmentally sound decision a car owner can make?
Jason Lancaster is the editor and founder of AccurateAutoAdvice.com, a website committed to giving car owners quality automotive advice that they can actually trust. To see more, read Jason’s scathing review of HHO fuel systems.