A quick guide to electricity meters and EV charging

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  • #164585 Reply

    I’ve seen a few posts regarding people having problems having an EV charger fitted as their “meter” or equipment is insufficient to allow an EV charger to be fitted without extra work. This work is usually free if by the DNO (local grid electricity supplier different to your electricity supplier), electricity suppliers vary. This can be a slow process so it needs looking at early.  If you thinking of getting an EV charger here is what I have found out whilst researching this topic.

    1) Everying up to the main fuse (just above the red circle) is the responsibility of the DNO. The fuse needs to be at least 80amp (likely to be 40 or 60 amp traditionally) and you don’t have a looped supply. A looped supply is where two or more properties are connected to the main cable in the street via one cable, very common on older properties (especially semi-detached). If you look in the red circle you will see 2 cables coming out of the main fuse. One is the supply, the other goes to my neighbour. Before an EV charger can be fitted the supply must be unlooped by the DNO. The DNO doesn’t charge for this.

    2) The “tails” (green circle) – cables from the fuse to the meter and from the meter to the isolator switch (blue circle) must be 25mm square cross-section this has a diameter of approximately 11-12mm if yours are less than 10mm you probably have 16mm square cross-section which need upgrading. This should be done if you get a smart meter fitted.

    3) An isolator switch (blue circle)  is often a prerequisite for having an EV charger fitted. This allows the supply to be isolated without removing the main fuse with is against what most DNO’s allow.  If you are lucky this will be fitted when your smart meter is fitted and done for free.  If not done with the smart meter install, its down to whoever you pay your bill to and can be costly.

    Hope this helps. I’m writing this in September 2021, not getting an EV till June 2022. Yet my EV charger fitter has strongly suggested applying to the DNO now as it can take months for this all to happen.



Viewing 7 replies - 1 through 7 (of 7 total)
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  • #164692 Reply

    Admin – might this be a good post to make sticky?

    #164694 Reply

    Great post Jacippit..

    If I was looking at having EV charge point installed I would definitely go down the Smart meter route. When arranging the smart meter install, if you mention EV or consumer unit upgrade and you require 25mm tails and Isolator then it will be done within the meter upgrade free of charge. If this isn’t arranged upfront though and the existing is 16mm cable then 16mm will stay in if the DNO fuse is less than 100Amp. They won’t fit an isolator either unless prearranged. Most fitters I’m sure will upgrade cable and fit isolator if asked nicely however a lot of this type of work is sub contracted out by suppliers and they might be paid price per fit so will do the bare minimum.

    By the way if that’s your install then the cable to me looks like 16mm?

    #164699 Reply

    Measure the tails they are around 12mm diameter.


    #164748 Reply

    mine are 12.5mm so should be ok. its a fairly new meter too.  so as my supplier is always wanting me to take a smart meter, should i insist they fit an isolator at same time or no deal?

    #164757 Reply

    What happens if your electric meter is housed in the outside standard white wall box and there is not enough room to fit all what is in your picture ?

    #164759 Reply

    What happens if your electric meter is housed in the outside standard white wall box and there is not enough room to fit all what is in your picture ?

    Everything in the picture with the exception of the large white metal box on the right is the responsibility of the DNO or your supplier and will fit. With regards to anything else, you need specifically for your EV charger your installer will advise on the best way to do it.

    #164872 Reply

    Thanks to Jacippit I am soon to be ordering an EV (ID.4) so this thread has been very useful. It will be many months before the vehicle will be delivered but that is good I suppose as it could take a while to get the charger sorted.

    The dealer I will be ordering the car from said there is a form to fill in when ordering the car so that motability can get the charging point organised so will have to see if that happens when I order the car next week.

    In the meantime I have been able to check a few things with the help of this thread. I have my electrics all in a largish cabinet at the foot of the stairs near the front of the house. The house is a 1930’s solid brick house with no cavity, the power rises out of the ground within this cabinet and fortunately is not looped and also the fuse is 100 amp so that gets me over the first two obstacles. We had some major refurb done about 3 years ago when we had a new kitchen amongst other things and most of the electrics down stairs were renewed along with a Schneider Easy 9 consumer unit. The rest of the house had been rewired approx. 25 years ago anyway and about 4 months ago we had a smart meter installed under our power supplier Octopus.

    The wiring from the 100 amp fuse to smart meter and onto the consumer unit appear to be 25mm squared cables so that is the 3rd obstacle cleared and only thing not sure about right now is whether we have or need earth boding in place or not to the gas meter box which is outside.

    Anyway other than that we should be good to go and can hopefully get a free installation from motability.



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