What would a clean-sheet set of wiring regulations look like today?

Standardisation of wiring colours would be a useful step. Green/Yellow for ground/earth is almost there but the rest of the colours are scattered in function between the different countries. If I remove a light fitting in my Swiss apartment I may find a black wire and a yellow wire. The black is phase, the yellow is neutral. 

Redefining any of the current colours would merely increase the already huge legacy problem 

DShutt said:

I don't think the battle between AC and DC charging for EVs has finished yet - the IEC 62196 connector might not have a long term future.

DC has clearly won for higher power charging.

I think it's basically an economic argument in favour of AC currently, the advantage of AC is that the charge-point is simple and cheap, it's an AC contactor/relay with some simple car-to-charge-point handshaking and signaling, along with some electrical protection - RCD, over-current, loss of PEN for some installations and more recently, some basic "smart" functionality. AC also allows Mode 2 charging using simple plug-in 'granny' chargers at any location with a suitable AC socket.

A DC charge-point is inherently a lot more complex as it contains the power conversion equipment, but what benefit does this bring in a domestic setting? The AC charge-points already provide upto 7kW which is hitting the limits of typical British domestic household supplies. Public charge point operators could already fit DC chargers if they wanted, but they tend to fit them more sparingly because the DC units are significantly more expensive than AC charge-points, plus to offer much faster charging / higher powers  then requires a larger capacity electricity supply which then costs the charge-point provider more (commercial customers pay standing charges based on their connection capacity).

DShutt said:

Domestically, if you could charge your car twice as fast, didn't have to pay for a £500 built in charger option and had the possibility of V2G operation, how much would you pay for a home DC charger?    How.much would it cost to make a 15kW bi-directional inverter charger?  I don't think the difference between those two numbers is that great...

It's the economics which rule, it doesn't make sense to have universal high-power DC charging. If anything, the economics point to the use of lower capacity, or more intelligently controlled AC charging and certainly in domestic settings.

I wonder how many hundreds of millions or billions of pounds, all paid for by us customers, is going to be wasted over the next few decades, upgrading lower capacity or looped supplies to GB homes because of some theoretical possibility of over-load when charging at 7kW, when some smart controls (dynamic / real-time adjustment of charging current to manage load on incoming supply) could avoid the need for upgrades at lower cost. If people started installing 15kW charge-points the issue would be even worse.

I very much like the French approach, where households have a defined supply capacity, which has a value and if you want a bigger supply you pay more for higher capacity options. That reflects the reality - capacity costs money. It drives rational decisions - that capacity costs money, and once people start paying for that capacity, they start using it wisely and carefully.

Hi,

I agree the economics matter - but whose economics?:

• Yes, a DC charger has a cost but at the moment car manufacturers are supplying one of those with every car.  I suspect they would be delighted to stop doing that and reduce the cost (and reduce the weight and potentially increase the quoted range by a mile or two) of the car.  The economics here would point to manufacturers omitting the charger from the car.
• As I can charge at home, I have no use for public AC charging facilities, they are too slow for use away from home where I am normally in a hurry.  I would be surprised if public AC charging points make as much money as DC points unless they are located such that they are used by those who don't have access to their own charging arrangements.  AC chargers deliver less power which means less income per charger.  I'm not sure the economics (in general) favour public AC charging.   
• The most common car charging tariffs offer ~5 hours of cheap charging a day.  At 7kW that won't charge the batteries in larger EVs.  I accept that that only matters if you frequently do significant mileage but some people do.
• If you have more than one EV then being unable to fully charge one of them overnight introduces inconvenience.  As someone in that situation, I (occasionally) end up fixing that problem by using a 7kW charger and a 3kW granny charger overnight at the same time.  The (admittedly limited) subset of people like myself will probably end up occasionally demanding 15kW with two AC chargers anyway.
• For the consumer, the economics are skewed towards being able to take advantage of cheap electricity whenever it is available.  The larger the charger, the more likely that they will be able to maximise the benefits of the availability of cheap power.  The whole concept of cheap rate electricity is to push consumers to concentrate demand at certain times of day - I suspect there is a conflict here between what suits the transmission / generation system and what suits the distribution system(s).
• The DNO certainly won't like peaks of demand in excess of the rating of their local distribution system.  Those economics are not currently exposed to the consumer and at present there is no mechanism to do so.  There is the scope to introduce tariffs which limit peak demand but doing so is likely to be very messy - off peak tariffs encourage the use of electricity at certain times, it is likely to result in a degree of discussion if the message turns into get "cheap electricity between midnight and 05:00 but don't use too much".
• It is the DNO who think that unlooping is necessary.  If it really isn't why are they spending the money?  Why haven't the DNO simply put out a standard for a CT on the shared incomer and a current sharing mechanism for EV chargers - I'm guessing that the cost of the CT wiring isn't considered too different to the cost of unlooping?
• I've already commented a while ago in another thread on the wasted opportunity that smart meters represent in terms of providing metering data to equipment within the home - they also present an opportunity to offer tariffs which aren't quite as harsh as having a fixed maximum demand.  You could imagine offering consumers a tariff where the smart meter could be used to signal overload of the distribution system and prompt customers high demand equipment to throttle back.  This would offer the ability to manage peak demand on the distribution system where it presents an issue rather than increasing prices for all consumers, no matter whether there is a local limit or not.  Of course, my suggestion creates the same issues about performance uncertainty as exist when adaptive DSL is used for internet access.
• Moving the inverter for V2G from the car to the wall suits the car manufacturer, otherwise the car need to know where it is in order to know which grid standards to adhere to and be able to support them - that makes the inverter more expensive.  Its not an insurmountable problem but car manufacturers probably don't want to have to solve it.  Personally I have doubts about V2G but some people like the idea.

To be clear, I'm not saying that everyone should have a 15kW DC charger.  I'm saying that moving the power conversion from the car to the wall opens up opportunities and potentially cuts costs that the consumer is exposed to.  For a consumer buying a car and a charger, for a given rating, there should be little difference in cost between the AC/DC conversion being in the car compared to it being on the wall and there may be economic benefits in doing it that way.

Only time will tell where we end up.

DShutt said:

For the consumer, the economics are skewed towards being able to take advantage of cheap electricity whenever it is available.  The larger the charger, the more likely that they will be able to maximise the benefits of the availability of cheap power.  The whole concept of cheap rate electricity is to push consumers to concentrate demand at certain times of day - I suspect there is a conflict here between what suits the transmission / generation system and what suits the distribution system(s).

I think 3kW (let alone 7kW) of charging demand per car is probably enough to handle any glut of electricity. There are around 30 million cars in the UK, on average the vast majority are stationary and thus theoretically available for charging. If we could provide chargers, even low power ones, to cars wherever they go then we will be able to absorb enormous pulses of surplus electricity.

Say 15 million cars are available for charging at 3kW. The electric car system can then soak up around 45GW of overproduction on demand. At 7kW it will be 105GW.

Likewise if we can persuade everyone to have heat store style hot water (be it a cylinder or one of those compact stack of block ones) then we can soak up something like 90GW (at 3kW each) of surplus power, on command (At least in the short term).

If we assume that most electric cars will be plugged in at low demand periods, which may be night or the middle of the day, the amount of electricity each individual car will have to absorb to eliminate gluts will be relatively small.

I actually considered some of this when I did my PhD thesis. I concluded that total decarbonisation, without resort to amazing efficiency assumptions (or even heat pumps!), can probably be achieved in a world with 100A single phase supplies were the predominant domestic supply, although massive reinforcement would be necessary to meet the low voltage demands. Albeit it should be possible to avoid wrecking every street.

Average car mileage is only 7,700 miles per year after all, or about 20 miles per day. That's only about 5kWh at 4 miles per kWh

Even with only 5 hours of charging, a 7kW AC charger will pull down something like 35kWh, or around 140 miles per night.

I am sceptical there are really many people for which this is unacceptable, and in that case by far the lowest capital cost solution would likely be to just tolerate charging at slightly higher rates on a longer duration.

Economy 7 would get you 49kWh after all.

MOT statistics seem to indicate only around 5% of vehicles are driven more than 15,000 miles a year, which still only amounts to 40 miles per day, on average.

Taking your points in turn:

• Yes moving the AC-DC conversion from the car to the charge-point would reduce car manufacturing costs, but it then increases the charge-point cost by a similar, or possibly greater amount, so domestic charge-point cost and public EV charging costs would have to increase to cover this extra infrastructure costs.
• I can't see it being realistic currently because of the restriction on charge-point access, where DC charging infrastructure is still relatively limited and AC charging is pretty much essential to avoid range-anxiety / accessing most public charging. DC rapid charging is also more expensive than AC public charging (p/kWh), reflecting the higher infrastructure cost of the DC rapid charge-points.
• Your experience, I would suggest, reflects that of typical early adopters who normally have their own off-road parking and their own home charging facilities, but going forward EV ownership needs to expand to include motorists without home charging. So where are these drivers likely to charge? Currently it looks likely this will be a mix of road-side charging (lamp-post charge-points, kerb-side charge points), workplace charging, public car parks, shops/leisure venues.
  • Some of these 'use cases' are not suitable for rapid charging, with people rapidly moving their EV once charged, they rely on the vehicle being plugged in and left to charge for long periods while the owner is busy doing something else, at home busy or asleep over-night, or during the day at work. These are not suitable for DC rapid charging, where the vehicle blocks the charge-point for long periods, resulting in poor utilisation of the infrastructure.
• For the tariffs savings, there's a trade off between high power charging at off-peak times to maximise unit cost savings vs. the cost of providing the home with the supply capacity and a suitably powerful charge-point to provide that. And when we get above 7kW per house, needing supply upgrades etc, then there's a question of whether it makes sense, or whether a different tariff design (for example, including the cheap, afternoon off-peak period for some extra hours each day) gives a better result.
• For the DNO domestic unlooping, the DNO recovers those costs as part of its regulated costs from bill payers and the consumer getting the unlooping does not pay the direct costs of the work, so there's no financial incentives on either of these to use technologies like smart dynamic control to maximise the use of the existing supply capacity. 
  • The UK should learn from France and adopt their system of having defined supply capacities, with standing charges based on those charges, that provides financial incentives to use smart / innovative controls and use existing infrastructure more optimally. 
• Re. smart meter control, yes that largely what the French Link smart meter did, had an accessible serial port with real-time metering data and control signals for loads, signals when the off-peak rate was live etc, to support these types of smart controls. The GB smart meter design was much more basic and limited, the old auxiliary load control switches plus a later attempt to graft on some proportional load control capability which didn't deliver much / scale-up.

I suspect the long term outcome will depend on what happens with power conversion technology and costs, if 7kW DC charge point equipment falls in cost/size/cooling requirements, to the point that a DC charge-point is competitive we may see more DC charge points appear. If V2G takes off, that might accelerate the uptake in the domestic space.

I suspect it's likely going to be at 10 years or more until DC charging starts squeezing AC charging out.

Going back to the original question about rewriting the Wiring Regulations for today, I think a good point coming out of this discussion on EVs is that in our electrified homes and businesses, there will be more high power loads like AC / DC for EV charging, heat-pumps, water heating / showers with a total maximum power demand far beyond anything that can reasonably or economically met by simply increasing the supply capacity.

So the topic of load diversity and the use of smart / dynamic control of loads becomes much more important to ensure that installation design is economical and efficient.

DShutt said:

off peak tariffs encourage the use of electricity at certain times, it is likely to result in a degree of discussion if the message turns into get "cheap electricity between midnight and 05:00 but don't use too much".

Or rather spread out the usage rather more evenly over time ... e.g. my supplier offers an EV tariff between 0000 and 0500 but the Heat Pump tariff runs from 0500-0900 (and then 1300-1600).

With the advent of smart meters it should be possible to smooth things further - e.g. one group of customers get 2300-0400 another gets 0000-0500 and another 0100-0600 say. Loads will tend to be higher when off-peak starts then decline as less than empty to start with batteries become full (or charging rates reduce above the 80% capacity mark). All sorts of possibilities to protect looped supplies or overall distribution capacity.

  - Andy.

TurboGen said:

So the topic of load diversity and the use of smart / dynamic control of loads becomes much more important to ensure that installation design is economical and efficient

And safe ... where are the system standards for this technology, that ensures the load curtailment provisions don't get into an unsafe condition (i.e. cause overloads) when things go wrong ... particularly long-term small overloads are potentially the most damaging (larger overloads can be covered by operation of overcurrent protective devices)? There is a functional safety element to this.

As always seems to happen, whenever something gets discussed here, eFixx has a new video on it: https://www.youtube.com/watch?v=Fl3kpGxYvcs

But you do need a stack of up to 5 off 5kWh battery packs, and also a decent amount of power to the grid. At the end of the charge, the batteries will be flat, so no running the house off them until they charge again.

The whole lot looks really expensive when compared with a standard 7kW EVSE.

See also https://www.sigenergy.com/en/products/dc-charger

Yes quite and that's something which you want covered in the 'clean sheet' Wiring Regulations because these smart / dynamic load controls will be or already are, an integrated part of many different types of consumer or commercial loads each with their own respective standards, so it needs some overall / wrap-around requirements which presumably could be part of the Wiring Regulations which is bringing those products together through the fixed wiring installation.

Thinking about a future electrified home, it's not unreasonable to expect it may have:

7.4kW EV charge point = 32A

9kW (thermal) heat-pump - typically 4.6kW = 20A electrical (worst case cold-weather / poor CoP conditions)

Hot water cylinder back-up/legionella heater 3kW = 13A

Home BESS 6kW = 26A

Electric cooker = 20A

Sockets = 32+ A

That totals up to 143A before you add any additional socket circuits, lighting, electric shower, possibly an air-conditioning unit etc. 

Now in practice there will be some fortuitous diversity, but given the growth in time of use tariffs incentivising off-peak consumption which result in loads being synchronised to operate during those periods, it's not unreasonable to think there may be periods where the EV is charging at full power, the heat-pump is running flat out to provide space heating, the legionella cycle may be running on the hot water cylinder, the home BESS may be charging up and appliances are running.

It strikes me that smart / dynamic load controls are inevitable if the future, electrified home is to be feasible and so the Wiring Regs needs a good framework for handling this topic going forward.

My understanding is that the National Grid DNO operation (is that Western Power Distribution?) has started replacing 100A cutout fuses with 80A fuses, because the traditional "peaky" loads are being replaced with more continuous loads such as EV chargers. The report I read suggested that they are concerned with the true rating of their service cables under continuous load.

I agree that some sort of standardised, non proprietary, control apparatus is required. I doubt the signalling channel needs to be particularly fast, a 16 bit 'half precision' float every second or two from a meter giving current on the inlet cable is probably sufficient to avoid a slow overload.

I know I keep going on about it, but the recent DALI-2 standard could easily do it! However that would require cables. It could probably be done with something like power line signalling but that would require some method to prevent the signal interfering with other houses on the same feeder. Wireless could also do it, but I would worry about the integrity of available low cost wireless formats, and an accidental misconfiguration or dropped signal could get very expensive for a householder if it blows the DNO fuse.

DALI in the house for everything has some simplicity to it, and makes it all strictly plug and play with no worry of accidentally linking to something next door.

I think all this reiterates that all new supplies should be at least two phase, and probably three phase since I doubt it costs much more.
That itself has interesting implications - 400V single or three phase would be available for large appliances.
1.5mm T&E can supply an awful lot more at 400V than 230V!

My understanding is that the National Grid DNO operation (is that Western Power Distribution?) has started replacing 100A cutout fuses with 80A fuses, because the traditional "peaky" loads are being replaced with more continuous loads such as EV chargers. The report I read suggested that they are concerned with the true rating of their service cables under continuous load.

I agree that some sort of standardised, non proprietary, control apparatus is required. I doubt the signalling channel needs to be particularly fast, a 16 bit 'half precision' float every second or two from a meter giving current on the inlet cable is probably sufficient to avoid a slow overload.

I know I keep going on about it, but the recent DALI-2 standard could easily do it! However that would require cables. It could probably be done with something like power line signalling but that would require some method to prevent the signal interfering with other houses on the same feeder. Wireless could also do it, but I would worry about the integrity of available low cost wireless formats, and an accidental misconfiguration or dropped signal could get very expensive for a householder if it blows the DNO fuse.

DALI in the house for everything has some simplicity to it, and makes it all strictly plug and play with no worry of accidentally linking to something next door.

I think all this reiterates that all new supplies should be at least two phase, and probably three phase since I doubt it costs much more.
That itself has interesting implications - 400V single or three phase would be available for large appliances.
1.5mm T&E can supply an awful lot more at 400V than 230V!

EIreland said:

I agree that some sort of standardised, non proprietary, control apparatus is required. I doubt the signalling channel needs to be particularly fast, a 16 bit 'half precision' float every second or two from a meter giving current on the inlet cable is probably sufficient to avoid a slow overload.

I agree, to avoid the current situation of duplication of household load monitoring devices - a CT for the BESS, possibly an extra CT for a stand-alone solar inverter, CT for the EV charge-point, a CT for the heat-pump, some of these have remote DIN rail meters, so the amount of duplicated equipment at the meter/CU becomes significant. But also it needs some standardisation to handle how to coordinate the sharing of available capacity between loads.

That said, I think when you get into these detailed load monitoring design, communication standards, arrangements for capacity sharing and prioritisation between loads, this is a taking you toward a separate, technical standard to cover this aspect as it's beyond the scope of the Wiring Regulations.

For the Wiring Regulations, I was thinking something more high-level around how these smart controls should be used when designing an installation and determining maximum demand - what allowances need to be made for minimum loads from these different load types, how much turn-down / load reduction is acceptable, some form of framework for design.

Also re. Graham's point on the safety topic, what approach the Wiring Regs take to providing additional overload protection for multiple dynamic loads. There's conceivably quite a number of different ways this could be achieved, each with various pros and con, so having some standardised approaches within the Regs is likely to ease and simplify this.

Whilst I agree that such systems are somewhat beyond the scope, I think the best way to avoid a zoo of incompatible equipment, with all the problems that causes for the householder, would be to specific a communications standard, if only a physical layer, to be used.

If we go with a DALI compatible physical layer, as an example, the wiring regs could reasonably impose a pair of thin data cores into cables in the same way they impose an earth conductor. It is a bit beyond the traditional view of BS7671, but if we can redesign wiring regulations (and their related regulations like the socket regs), we could impose such things if we wish.

I think smart controls using a single unified spec an excellent way to rationalise the current arrangements for lighting and the like that cause such issues in the field. If we have digital control of lighting just written into the specification, as an example, new installations never have to worry about the pain of two or three way switching and the confusion it can cause.

Such things are often referred to in the context of confusing DIYers, but during recent work in my house an apparent professional electrician managed to rewire the lighting to put a dead short between a switched live and a neutral, so the breaker immediately tripped (complete with a spark visible through the gaps in the casing!) whenever a certain switch was closed.

Just think of all the hours of fault chasing that could be eliminated if lighting was always "wire up like colours"? That could meaningfully ease the burden of the current electrician shortage and thus meaningfully advance the goal of all wiring regulations - effective, affordable and safe electrical installations for all.
We now live in the era of smart technology, I think we should fully embrace it to gain its benefits. If we don't specify smart controls we will have serious problems with lock in, and the inevitable attempts to turn literally everything into an "app".

Also we could have the remotely switched sockets that the Americans always sing the praises of! Without the problems of their American implementation.

EIreland said:

I think all this reiterates that all new supplies should be at least two phase, and probably three phase since I doubt it costs much more.

This may be a bit Jack, but I am in the lifeboat (to combine both Army and RN turns of phrase).

I don't think that my 3-phase supply was significantly more expensive than single phase. OK, the service cable and service head would have cost a little more, and of course, there is a little bit of extra labour in joining four rather than two conductors. However, getting to site and digging the hole in the road is the same.

EIreland said:

My understanding is that the National Grid DNO operation (is that Western Power Distribution?) has started replacing 100A cutout fuses with 80A fuses

We have coped on a 60 A fuse for years and, frankly, if you are above that level for a significant amount of time, your leccy bill is going to be eye-watering.

Don't think that a 3-phase supply at home is going to get you 69 kW on demand. My contract is for 30 kW ADMD even though the fuses are 100 A. Similarly, I understand that the standard contract is for 18 kW (i.e. 80 A) for single-phase domestic.

Chris Pearson said:

We have coped on a 60 A fuse for years and, frankly, if you are above that level for a significant amount of time, your leccy bill is going to be eye-watering.

I'm sure that 60A was plenty when my house was built in 1968. But now it's starting to look a bit weedy.

If I plug the car in to charge (7.2kW*) and take a shower (7.5kW), then that's the entire supply capacity for the house.

I'd like to install an A2A heat pump one day, in place of the gas central heating. But that's another large load that could be running for hours on end. Plus I would have to use the 3kW immersion heater overnight for the hot water.

Realistically, any new house should be wired 3 phase, and maybe an upgrade programme for older houses that need it.

*Actually my EVSE is currently set to 5kW, for reasons.

Simon Barker said:

I'd like to install an A2A heat pump one day, in place of the gas central heating.

In which case you'd have the option of using the HP for (pressurised) hot water too - so no need for the instantaneous electric shower - so that's 32A freed up (before diversity).

In France, I gather, instantaneous electric showers as we know them are practically unheard of (because of their 32A or 40A single phase supply limitation) - their way of doing an electric shower is an immersion heater in a pressurised cylinder run off-peak - generally more expensive to install, but better flow, cheaper to run and fits naturally between larger daytime loads like cooking.

   - Andy.

Simon Barker said:

If I plug the car in to charge (7.2kW*) and take a shower (7.5kW), then that's the entire supply capacity for the house.

Surely, you can arrange your routine so that you charge the car and shower at different times. ;-)

I agree that load control has an important part to play, but I think one of the most important advantages of electricity is that the householder can use lots at once if they need to. I'd be very worried about diluting that advantage. After all, decarbonisation will require people to use a great deal more electricity than they have before, even if the heat pump rollout delivers everything that is promised.

We could quite easily end up in a situation where we have a 32A car charger and a ~20+A heat pump running continuously for hours. Especially if the 7kW charger load swaps between two vehicles in sequence. That wouldn't leave much for things like a cooker on a 60A or even a 100A system.

I would think that any future supplies should be based on 2 or 3x100amp supplies.

We do have an example of a highly electrified society, in Quebec. Now obviously their heating loads are way more extreme than in the UK, especially in a heat pump future, but they also don't have huge penetration of electric cars there. 

Typical electrical installs there are 240/120V split phase systems with 200A on each side. That's something equivalent to a 200A supply in the UK.

I don't think the terminations or the cost of the cable is really a major driver on supply cables, so I see little reason not to provide people with a three phase supply. I think we should be aiming for major growth in electricity use as it displaces all other fuel sources, after all, using more is a good way to make electricity cheaper by amortising fixed costs - doubling the rating of a distribution system doesn't double its capital  or operating cost after all.

Do French Linky type meters simply open the contactor instantaneously if the current flow goes over a set limit, or are they sophisticated enough to run a current history model?

EIreland said:

Do French Linky type meters simply open the contactor instantaneously if the current flow goes over a set limit, or are they sophisticated enough to run a current history model?

The traditional French approach to was for the supplier (EdF) to supply a kind of adjustable 500mA RCBO (like this: www.manomano.co.uk/.../itron-400020-differential-circuit-breaker-edf-2p-60a-500ma-selective-sdb-ii-500-60a-s-6422703 ) at the demarkation point - the 500mA RCD provides a starting point for ADS (as their supplies are all TT) and the little window shows the current setting - usually 30, 45 or 60A I think. I believe the current setting is sealed and if tripped it's a call to the supplier to get it reset (and repeat offenders are 'offered' a higher (more expensive) option. I presume the underlying mechanism is similar to the thermal element of an MCB, but that is a guess.

I don't know if they're sticking with the same approach with smart meters.

   - Andy.

EIreland said:

We do have an example of a highly electrified society, in Quebec. Now obviously their heating loads are way more extreme than in the UK, especially in a heat pump future, but they also don't have huge penetration of electric cars there. 

Typical electrical installs there are 240/120V split phase systems with 200A on each side. That's something equivalent to a 200A supply in the UK.

The economics are very different though, Quebec has what are to British eyes, almost unbelievably cheap domestic electricity rates of around 7 CAD cents per kWh, that's about 3.5p/kWh. After the first 40kWh per day, that rate rises to the giddy heights of 11 cents, so 5.5p/kWh !

At those kind of prices, simple resistive heaters and storage heaters are a competitive form of heating.

With British domestic electricity unit rates around 5X that, the cost aspect will act to constrain demand in Britain.

Well yes, Quebec electricity rates are so low as to almost justify the old claim of electricity "too cheap to meter".

There is actually a cheaper tariff than the one you suggest if you have an auxiliary heat source to use in deep winter (defined as when the thermostat in your meter cabinet reads less than -12C!). That gives you 5.3 canadian cents per unit the rest of the time,  albeit with the cost of 30 canadian cents below -12C.
There is a reason  that Quebec has as many private pools per capita as California.

Whilst rates are in Ontario are much greater, they too have a time of use tariff with an overnight rate of only 3.9 canadian cents, or 2.1 pence per unit. That is a heavily nuclear dominated system, with their regular rates about 12 cents canadian per unit.

Off peak electricity will be extremely cheap in a renewable dominated system,although the times when it is used may be unpredictable.

If significant nuclear capacity is built it will be almost free. I believe before electricity market liberalisation, the "Option TEMPO" six-rate time of use tariff provided by EDF varied from 50 eurocents per unit to only 3.

We won't reach canadian levels, but the average electric car charging load will be something like 10GW, based on existing car mileage. If car mileage goes up due to low marginal costs, it will be more. We should expect radically more use than before, and this will probably drive down unit costs by amortising fixed costs.

EDIT: The cost delta per unit between my energy providers 'Economy 5' EV tariff and gas is getting much smaller than it has been in the past....