Old car or new car?

Every few years most of us face a big decision: is it time to buy a new car? Our old trusted vehicle that has carried us so well has gotten too rusty to pass inspection or too old to assure us of its continued reliability. What environmental considerations should underpin a decision of which new car to buy?

First, we want to ask about the environmental impacts of buying a new car. Across a range of size, the energy it takes to manufacture a new car is equivalent to about one year of the energy used to power it.  Replacing a “clunker” just because it’s a “clunker” is less important than how long you plan to keep the new car. If you plan to keep a new car 5 years, it should get 20% better gas mileage than your old car if you want to approach environmental neutrality in your decision to buy.  If you will keep a new car 10 years, then you only need to get 10% better mileage.  A national program to get old cars off the road is only effective in concert with higher Corporate Average Fuel Efficiency (CAFÉ) standards that raise gasoline mileage by at least 10% each year.

Hybrid cars have been available for more than a decade. These advertise impressive fuel efficiency, but their higher price means that unless gasoline prices rise substantially, you cannot expect to recoup the initial investment in a hybrid for many years.  Buy a hybrid if you don’t mind paying a little more to make a statement for the environment.

We’re hearing more and more about electric cars, especially from Tesla, whose CEO Elon Musk has invested billions in a battery factory and assembly line outside Reno, Nevada. The driving range of electric cars has improved dramatically—you can go nearly 300 miles in a Tesla before recharging.  And the time to recharge it has dropped dramatically. So, if you live in an urban or suburban landscape, an electric car looks good because you can recharge it every night.  If you live in a small, rural town in Kansas, an electric car is not for you.

Electric cars are also touted as pollution-free—no tailpipe emissions of CO2, NOx and other air pollutants that harm the environment.  That is, of course, not entirely true, since electric cars must charge up from the grid, which is dominated by coal-fired power plants that emit these compounds.   At least, the emissions from power plants, because they are localized, are more easily controlled and captured than the disaggregated emissions from a fleet of automobiles.  And, as our electricity is increasingly generated from wind and solar power, the power plant emissions will diminish.

Electric vehicles are said to be more efficient than gasoline-powered models, inasmuch as they convert 60% of the power from the grid to propel the motion of the vehicle, versus only 20% from gasoline-powered models. That comparison is also not entirely accurate, since the electric vehicle was powered by a distant power plant that may have had only 33% efficiency, and the conventional automobile is powered by gasoline, which was refined from crude oil at about 60% efficiency. Thus, the energy efficiency of the electric car is only marginally higher than a traditional gasoline-powered car.

If you live near recharging stations, buy an electric car. If you live in the country, buy a high mileage gasoline-powered or hybrid vehicle and plan to keep it 10 years.




Huo, H., H. Cai, Q. Zhang, F. Liu, and K. He. 2015. Life cycle assessment of greenhouse gas and air emissions of electric vehicles. A comparison between China and the U.S.  Atmospheric Environment 108: 107-116.

Lambert, J., C.A.S. Hall, S. Balogh, A. Poisson, and A. Gupta. 2012. EROI of Global Energy Resources. State University of New York, Syracuse.

Lave, L.B. and H.L. MacLean. 2002.  An environmental-economic evaluation of hybrid electric vehicles: Toyota’s Prius vs. its conventional internal combustion engine Corolla. Transportation Research Part D—Transport and Environment 7: 155-162

MacLean, H.L. and L.B. Lave. 2003. Life cycle assessment of automobile/fuel options.  Environmental Science and Technology 37: 5445-5452.

Viñoles-Cebolla, R., M.J. Bastante-Ceca, and S.F. Capuz-Rizo. 2015. An integrated method to calculate an automobile’s emissions throughout its life cycle.  Energy 83: 125-136.

2 thoughts on “Old car or new car?

  1. I’ve often wondered how the large batteries of hybrid cars figure into calculations of their “environmental neutrality”, especially since the batteries may have to be replaced after ten years. I am willing to pay the extra cost for a hybrid car, but would prefer to know if it really makes a difference.

    1. Not sure I have a great, immediate answer to this question, which might make a good subject for me to research for another blog post.

Comments are closed.