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Calculate WLTP CO2 from NEDC CO2

  • 01-01-2022 12:33pm
    Registered Users Posts: 1,453 ✭✭✭

    Thinking of bringing an MB E400d in from UK this year at some stage, might wait till mid year and get a 192 (69) reg. Anything less than £40k.

    Want to be sure what VRT rate and then yearly motor tax I’ll have to pay as I believe all cars registered here from 2021 use the new WLPT figure.

    They only seem to display WLTP CO2 figures for cars from 2021 onwards which I won’t be buying!

    Is there some way to obtain the WLTP CO2 figure for this car for example that shows a NEDC CO2 of 158 g/km?



  • Registered Users Posts: 5,406 ✭✭✭User1998

    Petrol: y = x(0.9227)+34.554

    Diesel: y = x(1.1405)+12.858

    Eg. A NEDC tested petrol car has a CO2 value of 110 g/km on the vehicle registration documentation which would attract a rate of 16%. Revenue uplifts this CO2 value to a WLTP equivalent value as follows:

    y = 110(0.9227) + 34.554 y = 136

    This car is then subject to an 18% VRT rate.

    And don’t forget to add €20,000 on top of the purchase price for customs fees

  • Registered Users Posts: 1,453 ✭✭✭rodge123

    Hmmmm think I’m gonna have to re look at my choice of car! 😭

    Looking at 193 g/km when those calculations done which puts it into 41 bloody percent VRT and also moves it into 780 motor tax.

    Think they have upped the rates for 2022 onwards for vrt…was sure there was a 31% rate for 170-190 and then a 36% for 190+.

    Thought might squeeze under 190 and get 31%.

    Now it’s just 35% for 170-190 and 41% for 190+.

    Just notice now that they have those calculations you gave me there too.

    Had planned to avoid 10% import duty by buying under 3 year old car that was brought into UK from EU. Was also gonna only get Vat qualifying car to get 20% off UK price.

  • Registered Users Posts: 1,453 ✭✭✭rodge123

    Now it does appear that some of the 2021 ones are saying 189 g/km and others 192 g/km as WLTP.

    Only difference I can see in specs are the 192 g/km ones saying 340hp vs 330hp on the 189 g/km ones.

    I wonder if it is just mistakes made when adding the listing or were there different models available with 330 vs 340hp.

    Very confused!

    Not that really matters, I imagine a 2021 one won’t be within my budget for at least 12-18 months.

    Looking at review and they slay it’s 325hp and 189 g/km for the Sept 2020 facelift version… surely all the 2021 ones should be that spec too.

    Maybe a late 2020 one could come into budget sooner if used market came somewhat back to normal. Doesn’t look like sterling exchange to euro will improve though.

  • Registered Users Posts: 5,406 ✭✭✭User1998

    I think the conversion of NEDC to WLTP only applies to VRT and not to road tax. I have imported several cars this year and haven’t been hit with any crazy motor tax bills

    If you buy a 3 year old EU built car that was imported to the UK you will still have to pay 10% customs duty. The only exemption is if the car was built in the UK. If you google Rules of origin, or Preferential treatment, you should get more info.

    And as far as I know Mercedes were never fond of selling to Irish customers so I doubt they will sell you a car ex VAT, but its worth a try. Apparently its difficult to get sellers in the UK to sell the cars ex VAT.

    If you do manage to get a car, you should really be looking at hybrids or plug in hybrids as anything else is not worth importing. There are diesel hybrid and plug in hybrid options for the E Class

  • Registered Users Posts: 1,453 ✭✭✭rodge123

    According to this you shouldn’t have to pay import duty on car if was originally exported from EU and then re-imported within 3 years. No mention of rules of origin.

    Scenario 2.2 in that document is quite clear that no import duty applies.

    Got than from this this post.

    Interesting point on motor tax.

    Yeah think I read before that MB were awkward selling cars abroad, will see if how things work out.

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  • Registered Users Posts: 5,406 ✭✭✭User1998

    That’s interesting about the EU to UK scenario. I’l try look into that a bit more

  • Registered Users Posts: 4 Steeleyes

    Hi all I am new to this board, I have been tasked with a project based around NOx and CO2 and other particulates. I have researched this subject for a while and am yet to find a proper way of calculating this. I am told that the only way that NOx can be measured is in a testing lab, tailpipe emission test and that it cannot be measured properly any other way. I have now found the Irish revenue calculation and wondered how that worked? Any light on this subject would be greatly appreciated thanks in advance.

    Was wondering if someone could explain how exactly the revenue calculates the NOx part. If the CO2 is known what is the equation for understanding the NOx part?

  • Registered Users Posts: 5,406 ✭✭✭User1998

    Revenue don’t calculate NEDC to WLTP Nox, only Co2. The formula they use can be found online

  • Registered Users Posts: 4 Steeleyes

    thanks so how do they calculate a NOx figure? I see the formula but how does the formula work?

  • Registered Users Posts: 5,406 ✭✭✭User1998

    They use the figure thats provided on the registration certificate, or a certificate of conformity, or other official document

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  • Registered Users Posts: 4 Steeleyes

    ok great, thanks for your response

  • Registered Users Posts: 4 Steeleyes