Why are CO2 emissions important?

  • We take a closer look at how CO2 emissions affect tax
  • Find out why picking a greener car matters
  • There is so much choice for car buyers looking for tax-free cars

There’s been a great deal of talk about carbon dioxide (CO2) emissions over recent years, especially in conjunction with rising car tax costs, but what does it all actually mean and how does it affect you?

What are CO2 emissions?

Cars produce carbon dioxide as they burn fossil fuels, which is then pumped out of the tailpipe and into the atmosphere. Because there is so much being produced, plants and trees have no chance of soaking it all up.

All these leftover gases in the atmosphere are not only harmful to our health but also cause the overall temperature of the planet to rise. It’s suspected that this in turn causes the climate to change, resulting in heatwaves, floods, droughts and storms becoming more frequent around the world. 

The UK, like other countries, is under increasing pressure to reduce its carbon footprint (the amout of carbon it emits) and one area of key focus is the CO2 emissions produced by cars.

To incentivise car buyers like you and I into buying cleaner and greener cars, the government linked the amount of car tax you pay directly to the amount of CO2 emissions your car produces.

How does it affect the tax I pay?

Like we’ve said, tax and CO2 emissions have been closely linked to one another for a number of years now.

Manufacturers have come a long way over recent years, reducing the amount of harmful gases that are produced in their cars to meet the increasingly tight guidelines. There are more electric and hybrid (conventional fuel with electric help) cars now and hydrogen fuel cell cars are not far away from production either – all of these methods reduce the CO2 output of a car – never has there been so much choice when it comes to fuelling your car.

As you can see from the table below, the magic figure is 100g/km. If you can pick up a car which sits at this amount or below then you’ll have nothing to pay for road tax during the 2014/15 tax year. Up to 130g/km and you’ll pay nothing the first year, but choose a car above 131g/km and you’ll see the price you pay dramatically increase.   

There are plenty of cars that are now tax-free thanks to their sub-100g/km CO2 emissions, including popular cars like the Nissan Qashqai, Ford Fiesta and Audi A3.

You can also calculate your monthly car tax by using our car tax calculator here.

Stuck on which car to choose? Check out our car reviews section to find out more.

Petrol and Diesel Cars

VED Band

CO2 Emissions (g/km)

2014/15 first year rate

2014/15 standard rate


Up to 100
















































over 255




For cars first registered before 1 March 2001, car tax is based on engine size as official CO2 data is not available. For an engine which is 1,549cc and smaller the rate for this year is £145, and for bigger engines it’s set at £230.

What does the future hold?

New Euro6 legislation comes into force in September this year which states that average CO2 emissions need to fall below 130g/km across a car manufacturer’s entire range. There is also a further target for 2020 set at 95g/km.

In terms of tax costs, we will have to wait until the budget in March before we get confirmation, but considering how tight legislation has become and will continue to be, we can only imagine seeing the cost increase and the bands getting tighter.

Need help finding a low CO2-emitting car? Take a look at some of our other articles below:

Top 10 family cars for cheap tax

Electric cars – where are we now?

Quick guide to hybrids

Top 10 cars for 15k

Top 10 cars for young drivers

How much does a car really cost to run?