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Paul Kemp19/07/2021 10:34:38
710 forum posts
27 photos

PGK, 3.2 kW is a little over 13a on a 240v supply in basic terms so would be pushing a 13a socket to the limit. The charger has already been installed in readiness and the installer ran a dedicated 32a supply (single phase) which should just about support 7.4kW. Note however the comment the vehicle is only rated to take 3.2kW so the higher power charge would be pointless. Your 18p/kWh is pretty heavy,that's around 3p above the national average! Personally I would question the design of the vehicle in being a plug in hybrid with only 40 miles range on electric and limited to that charge rate. To me producing as a self charging hybrid would have made far more sense but not such a big tick in the green box. Choice of vehicle was governed by employer conditions and capital cost, an alternative would have cost a significant employee contribution per month which would definitely have vastly increased his personal costs.


Roger Best19/07/2021 18:19:35
369 forum posts
56 photos
Posted by Speedy Builder5 on 19/07/2021 06:37:16:

I can't remember what they are called, but I have seen several houses over here in France where the demand of the house is limited to the supply line by a relay device in the fuse box. When the house demand reaches the supply limit, all electric heating is "Throttled back". The electric heaters have 2 positions on them - Confort and Eco. Wiring to the radiators have 2 live wires, one for comfort and one for eco plus the normal neutral and earth. The switch is independent of the live supply and allows the user to manually throttle the radiator back.

I see no reason why the car charging point couldn't be fed by such a device as domestic demand is usually less at night.


Hi Bob,

Many if not most cars can be programmed to wait until they ask for electricity. Several chargers can do that too. Ideal for economy seven.

Andrew Entwistle19/07/2021 20:49:07
106 forum posts
200 photos

The latest smart EV wall chargers monitor the total power consumption of the house and scale back the car charging when necessary to keep within limits.

pgk pgk19/07/2021 21:18:39
2552 forum posts
293 photos

Paul Kemp
I wrote 16p - it’s actually 15 point something. There are far better tariffs, but they need a smart meter and that's not possible out here with no mobile signal. Most EV folk with a smart meter seem to favour Octopus, which i hear is as low as 5p at night.
I can't speak for other EV's but my car monitors electricity flows for unusual changes and adjusts itself. Also some folk just go with a 32A commando socket but I understand proper regs require OPEN protection (is it?) and a dedicated earth near the charge socket? I can set either the charge time or when i want a set charge to finish. I can also adjust things in the car remotely via mobile phone or internet


Paul Kemp20/07/2021 00:34:37
710 forum posts
27 photos

Apologies, so you did, brain playing tricks! 14.7p is somewhere around the national average so not so excessive. Yes it was Octopus he was talking about at 4p but I guess that could be anything up to 4.9! But you also have to factor in the increased standing charge to get that. Unless they program washing machine etc to run in the same period so a lifestyle and habit change to shift more than the vehicle charging to the cheap window the real cost is still more than 4 / 5p if considering only the vehicle. No doubt after an evaluation period he will have some numbers to support but with an average daily mileage Mon - Fri of around 80 with a maximum of half that on electric, without a long break for a charge somewhere he will still do the other half on petrol, it will be interesting to see how it pans out.


pgk pgk20/07/2021 06:50:02
2552 forum posts
293 photos

A lot depends on the specific vehicle. If memory serves the original plug-in Prius uses electric only below 30mph - fine if mostly urban commutes with braking energy harvested at any speed. It also helps if an employer provides recharge facilities at work. It's also true that some companies foist hybrid vehicles on their staff to greenwash their fleet with many never being plugged in..
Depending on where you live and how much one is willing to mess about (if it suits lifestyle) then slow chargers are often free in supermarket car parks and the like. Where i used to live before retiring the local Tesco has some 30 slow chargers in it's car park for a quick free top-up while shopping but not many folk will pratt about with cables just to save 3-4KWh at his charge speed.


Paul Kemp21/07/2021 23:46:19
710 forum posts
27 photos

I am intrigued to think about how car parks will look by 2030 and beyond, or even if they will be required - assumes the masses will actually be able to afford to have / use a vehicle. I currently park at the 02 in London when I have to travel to the office. Car Park 1 has a small charging station on one edge. Originally from memory (not that I really took note) there were probably 4 posts with EV sockets. I notice since the plague the area has been revamped with now probably six new charging points of which four I think are 'fast Chargers' and 2 slow. Where originally the posts were small blue affairs the new outlets are more sophisticated probably about the size of a petrol pump, there is new screens and notices limiting the amount of time you are allowed to park and charge (I think it's 2 hrs but it may be longer - again I have never taken that much notice!). The new charge point seems to be some kind of franchise operation with a coffee bar round the back. One notable difference is with the old posts (where I don't think there was a time limit) every post seemed to be occupied every time I passed by. Now with the new set up I don't think I have ever seen more than one vehicle hooked up at a time. I wonder is this because the cost to use them is vastly different or is the time restriction unmanageable? I guess if you go to a show or have gone to work the last thing you want to be doing is watch the time and break off to go and move your car? Maybe the EV owners are all isolating? Maybe for venues and work places intervals and coffee breaks will be replaced by move your car breaks?

I guess as EV use expands the ideal would be to have a post at every bay? Having a rough idea of the grid distribution in London and guessing the car park probably holds 1500 vehicles if every charger were 7kWh or more we are talking a pretty hefty addition to power requirements in the area.

From my marine work where we are talking tons of batteries providing 500kWh or more the charging requirements require dedicated 7kva supplies for some scenarios 11kva, things get very interesting in securing available supply and the costs eye watering.

Lastly talking to some industry experts there is a lot of doubt that the price of electricity will drop as the investment for renewables not only in construction but in running costs is high and the investment to improve distribution massive.

Intersting times.


pgk pgk22/07/2021 06:09:56
2552 forum posts
293 photos

Slow chargers of the 3.2 or 7.4KW type are usually cheap or free whereas new fast chargers (upto 350KW) are mandated to have a card reader option and are designed for top-ups during trips rather than use as a parking bay and overstay charges are there to improve availability to other users - some give you 10-20 mins after a full charge to disconnect or start debiting your card at £1/minute - but they do message your phone to warn you.
Electricity prices are going up such that some rapid chargers now have dual day/night rates.


pgk pgk23/07/2021 09:25:21
2552 forum posts
293 photos

Gov report into electric vehicle charger needs



SillyOldDuffer23/07/2021 12:15:59
8491 forum posts
1891 photos

pgk's link to the government's EV market study is interesting because it's much more concerned with finance and making the change happen than technical details. This is worrisome because politicians have a track record of skipping details in their costings, leading to budget overruns during the build. For example, HS2 costs are rising because the track survey was minimised when preparing the Business Case. I doubt an engineer chose to cut back on surveying the ground!

However, an interesting side-effect of what's going on behind the scenes to enable Electric Vehicles might be a big improvement to power available in out workshops! Depending on where you live relative to the network, installing three-phase is often prohibitively expensive, because, as Ofgem put it:

'Customers connecting to distribution networks currently face an upfront charge made up of the cost of new assets needed to connect to the existing network, and a contribution towards the reinforcement of existing shared network assets. This approach was originally intended to provide a signal to customers to avoid constrained parts of the network where expensive reinforcement is required.' (My bold.)

In other words, don't buy a shed miles from anywhere and expect the supplier to wire it up cheap for you! (See Roberts post quoting £45000 to replace 480V split phase with three-phase!) They want consumers to position themselves to suit the supplier.

As the 'signal' collides with the need to roll out many more car charging points, Ofgem propose to off-set the reinforcement charges, which might make it much easier to plumb our workshops with real 3-phase.


pgk pgk23/07/2021 12:42:21
2552 forum posts
293 photos


I have a 3phase 11KV line crossing my fields. From that a pole transformer and 250yd series of poles brings single phase to the house. It would be relatively trivial to give me 3-phase but the price estimates are prohibitive..


mark costello 124/07/2021 00:21:12
711 forum posts
12 photos

30 years ago I asked about getting 3 phase put in the house. The electric company survey said $2000 to bring it 1/2 mile to My house. Now They upgraded the pole in front of My house yes to 3 phase. I asked again as it is only 150' away on My land. Cost- $2000. no. Can't win.

Stuart Smith 524/07/2021 00:50:31
274 forum posts
40 photos


The first part of your quoted Ofgem statement is correct. However, I think the second (highlighted) part is something they have invented recently!

If an individual or company want an increase in their supply capacity such as changing from single phase to three phase , it has to be paid for somehow. The customer who wants the increase could pay for the total cost, part of the cost, or none of the cost. Any cost they don’t pay for has to be paid for ultimately by the rest of us. Ie the DNO might pay but eventually would be reflected in everyone’s electric bills.

This from Ofgem is interesting:


and this :


looks like they have been thinking about this since 2018, but haven’t decided yet.

Regarding the existing capacity of the electric network , a figure of 1.5kW per house has been used for many years ( but has changed - not upwards in recent years) as the ‘after diversity maximum demand’ (admd) for a house with gas central heating.
So the required capacity for the network and substation is worked out using a simple formula of (a x n) + a constant to account for loss of diversity amongst a small number of properties (was 8 kW but this may have changed). Where n = no of houses and a = admd.

It won’t take many 7.4kW chargers on all night to overload a network.



Edited By Stuart Smith 5 on 24/07/2021 00:50:51

Edited By Stuart Smith 5 on 24/07/2021 00:52:18

Paul Kemp24/07/2021 01:46:17
710 forum posts
27 photos

Stuart is correct on both counts from my experience. From recent discussions with our local DNO for a high capacity 3 ph supply their stand was the cable and sub station costs would be wholly to us. When asked if someone later wanted to tap into that supply what would happen, we were told in that circumstance the new customer would be charged a proportion of the fee for the supply we had paid for and we would then be refunded a proportion of that cost. The question was more from the perspective of preserving the capacity we were paying for than recovering cost so we didn't follow up on what proportion or if there was a time limit. Believe me the costs are not insignificant for either the cable - charged per metre including ground work or the sub station. Out of curiosity I asked about the situation with domestic supplies living in an area where the houses are a century old and the answer was in line with Stuart's point that without load balancing (rationing) through smart meters the main cables would need to be uprated. It can be done, it just a costs and someone has to pay - you can guess who the someone is.


Peter Ellis 524/07/2021 02:34:31
101 forum posts
11 photos

Interesting from a local perspective. I already have 3ph. The place was formerly a winery and used it for pumps.

There was another issue here. The network was originally based on 2kW per house, but has largely been upgraded to minimum 6kW, as the onset of A/C made it necessary. A/C units use 6kW. Larger properties might need more units. At one point, buying building land in some villages was pointless, as the electricity people wouldn´t guarantee a supply until the lines were upgraded.
With global warming, places like the UK will be using more A/C too, and the need to support this on top of supporting EV will be interesting.

Samsaranda24/07/2021 09:52:04
1400 forum posts
5 photos

In respect of charges for electricity supply works, our house is only single phase but 20 years ago we moved our meter from indoors to a box on the front of the property, this required a new cable joining the supply cable, the old cable was redundant. We were required to carry out all the excavation work necessary to expose the supply cable where the joint was to be placed and the trench to the front of the house. All the electricity company did was cut the supply cable, make the joint and connect the meter, I can’t remember the exact cost but I remember thinking that it was excessive for the work carried out. In contrast, at the same time we had the gas meter moved to a similar location , requiring similar works, I remember that the costs for the gas work were a fraction of that charged by the electricity guys, and they didn’t act like primadonas either. Dave W

Ady128/07/2021 09:56:43
5066 forum posts
734 photos

"Saving the planet" is going to be all about "Gouging the customer" in our brave new world

Electric car charging prices 'must be fair' say MPs


J Hancock28/07/2021 10:41:08
832 forum posts

Available this morning , the 'general public' view expressed in the Comments section , headed as ' Blackout Warning ' in the Daily Telegraph.

People waking up to what will happen . some amusing replies..

Peter Ellis 528/07/2021 11:32:06
101 forum posts
11 photos

A friend of mine, another model engineer, Barry Harrison, is the expert on brownouts. He did the reports on it for, IIRC, Sydney, Singapore and other cities, on brownouts that they were experiencing. They had experienced overloads in the winter, when heating requirements increased demand, but were now getting them in the summer months. In the winter, there was some offset in the cooler ground keeping underground transmission cabling cooler, but this wasn´t happening in the summer, when increased A/C usage was driving higher demand.

All this was before mass electric car recharging was even thought of.



Paul Kemp28/07/2021 23:30:12
710 forum posts
27 photos
Posted by J Hancock on 28/07/2021 10:41:08:

Available this morning , the 'general public' view expressed in the Comments section , headed as ' Blackout Warning ' in the Daily Telegraph.

People waking up to what will happen . some amusing replies..

Telegraph article to me was a bit speculative with references to MP's warning the Government and a historic quote from the boss of National Grid without an up to date quote or definitive references to back it up. Never the less from discussions I have had with UKP there is underlying truth. I do find it a bit of a worry though that "MP's are warning the Government" at this stage of the game! Surely Government is made up of MP's and they take decisions based on "advice". You have to question where the advice came from? Policy is set, the course charted with target dates so it's a bit late now to be posing a fundamental question such as how will all this power be distributed to point of use? Smart meters will undoubtably save us - or will they? Are they capable of limiting current on an external signal, outside interrupting it completely? Will we end up with load shedding consumer units? Are existing EV's equipped to communicate with the Grid to switch on or off or increase / decrease current draw for charge on command form the power supplier? Taking power from EV's to back feed the load is all very well but how will they know if you are intending to drive off at 04.00 just after they have drained your battery and assuming they had a good 5 hrs to put it back! That is without the increased discharge / charge cycles at the power company convenience reducing the life of the battery you paid for! I think there is a song about this........

Finally the easiest way to cripple a country now or into the future is to knock out the wireless connectivity and networks. With even your washing machine wifi capable you won't even be able to wash your socks, assuming the lights stay on!


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