“If you are thinking about replacing your existing car please do follow this advice and do your bit to make the UK a greener place to live.”

Tommy Geddes, Deputy Vice-Chancellor, University of Winchester

Why act?

Replacing a car gives you a great opportunity to be greener.

First of all consider do you need a car at all? If you own more than one car, could you live without one of them? Dispensing with your own set of 4 wheels opens alternative travel options, saving you the huge cost of insuring, taxing, maintaining and running a car. There are 113,000 vehicles registered in Winchester District, which has a population of 109,000.

If you must have a car, you can reduce your CO2 emissions and save money in fuel costs by buying a fuel-efficient car. The average petrol car in Britain achieves 28 mpg in town, 47 mpg in the country, and 39 mpg combined. Many small cars now available can achieve 80 mpg and large family cars can achieve 65 mpg for combined driving.

Thinking about carbon dioxide emissions, the average car produces around 170gm CO2/km.   It is now possible to buy new small cars producing less than 100gm/km. You can buy a new family car or a top-end quality car producing less than 120 gm/km. A car rated as less than 100gm/km costs nothing in vehicle excise duty; less than 120 gm/km a car has no vehicle excise duty in the first year and £20 or £30 a year thereafter.

So when you are buying a new or replacement car, look for one that does not produce more than 120gm/km. Think of the tax and fuel you are saving every year and the cut in emissions you are making. And think of the satisfaction of having a truly smart quality `green’ car outside your front door!

About my current car(s)






Actions to cut CO2

  • If your household has more than one car, get rid of one of them. If you replace it with a mixture of public transport and the occasional hire care or taxi, it’s much cheaper[i].
  • Create your down-sizing plan now so that you have planned how to cut down the number of cars in your household when one of them breaks down or wears out.
  • Explore options for car-shares, lift-share, car-pools and hiring now – lots of links at the end of this handout. 
  • Replace a car with a motor-bike or an electric bike.

Replace a petrol or diesel car with an electric car or a hybrid, especially if you have renewable energy such as solar panels. Electric cars are less environmentally friendly if they use fossil-fuel generated electricity, but even with the current UK energy generation mix, an electric car emits an average of 100g CO2 per km compared to about 120 for the most efficient diesel cars. Some 75% of energy produced by petrol engines is used in the production of heat. Partly because of the much higher efficiency of electric motors, the estimated energy requirement of an electric car is 15 kWh per 100km, about a fifth of that required by an average fossil fuel car[ii]

  • Some people argue that electric cars aren't a long-term solution to our travel[iii], because we’d need the entire potential UK supply of renewable electricity to replace all fossil-fuel vehicles with electric ones. But they are a good interim option, especially for shorter trips. 
  • If you can’t manage without a car, do your homework about the most fuel-efficient cars.
  • Manufacturer figures about fuel economy are unrealistic. Compare them with the independent figures given by Nextgreencar (http://www.nextgreencar.com/ ) or Fuel-economy (http://fuel-economy.co.uk/stats.html).
  • Don’t worry if the car you like seems quite light. A 10% weight reduction improves miles per gallon by nearly 7% and studies have indicated that the design of a vehicle is more important in terms of safety than its weight.

A word of warning… the emissions from manufacturing a car can be very large (about 6 tonnes for a small car and a whopping 35 tonnes for a large 4x4 car). So scrapping a car before its useful life is over for a new and more fuel-efficient one will actually increase your CO2 emissions for a period until your accumulated emissions savings from better fuel consumption exceed the emissions from manufacturing the new one.

My ideas







Time & materials

Two hours to explore the options using the web links, plus a couple of weekends to test drive your preferred options.

Suggested goals

Work out the cost of hiring a car when you need one instead of owning one.

Get rid of one of your cars and replace it with a motor-bike or electric bike.

If your car is nearing the end of its useful life and giving up a car is not practical for you at present, commit to replacing it within the next year with the most fuel-efficient car that meets your needs and which you can afford.

Co2 credit

Look up the emissions for your existing car in gm CO2 per kilometre on either http://carfueldata.direct.gov.uk/search-new-or-used-cars.aspx

or https://www.eta.co.uk/campaigns/green-car-buyers-guide/ and multiply this by 1.6 times your annual mileage (to convert to kilometres) to determine the emissions per year and divide by 1000 to convert from grams to kilograms.


Compare this for your new or replacement car (http://www.nextgreencar.com) and you can easily find out what your saving would be by subtracting the annual emissions from the new or replacement car from those for the old one.

My CO2 credit from swapping to a more fuel efficient car is _____________

For example if your existing car is rated at 175 gm/km and your new car is rated at 110gm/km and you drive 10,000 miles per year then your CO2 Credit is:

(175-110)*1.6*10,000/1,000 = 1040 kilograms or just over 1 tonne of CO2 per year.


What I will do











 Click here to return to the full list of greener travel factsheets.


References and links

[i] A taxi once a month to a supermarket four miles away, a hire-car four week-ends a year and a fortnight a year to go on holiday would cost £1015.43 (week-end car hire @ £35.96 = £143.84; 14 Days’ car hire = £263.59 Fuel for car hire 258; 12 supermarket taxis = £350). To run a four-year-old car worth £6,000 (MOT, insurance, and fuel and a 2,500 miles) according to the AA, would cost £2906 (Car tax (VED band F, 131 to 140g/km carbon) £130; Insurance £720; Capital loss of investment £236; Depreciation £1216; Breakdown cover £50; Running Costs: 2,500 miles at 21.95 pence per mile £548.75 incl. petrol at 12.9p per mile)

[ii] David MacKay “Sustainable Energy Without the Hot Air” http://www.withouthotair.com/

How to have the use of a car without owning one

Lower emission vehicles

The Environment Transport Association is an environmental alternative to the AA. Their website gives the green data on a car if you are buying one – https://www.eta.co.uk/campaigns/green-car-buyers-guide/