EV charge point approved with remedial works

[Marcus]

This feels like looking for solutions to a problem that isn't actually there (yet) to me.

Yes, if everyone with gas/oil CH and ICE car switched to a HP and EV overnight, then yes it would require a step change in DNO's infrastructure and their diversity calcs.

Considering heating:
In practice, it's going to take time (too much time perhaps), and in that time houses should become lower consumption (better insulation, better appliances), and those homes with direct electric heating would substantially reduce their demand when converted to HP ( i don't know what % of housing has storage heating or direct electric heating, but in these parts there is a significant amount - especially in rental properties).

EVs:
Ok, this will increase demand as more and more come online, but not every house will have a 300mile range tesla, and even if they did, few would be clocking 300 miles a day. If you only drive 50 miles in a week (quite a few car owners do less than that), your charger isn't going to be running at 7kw for several hours every night.

So yes household demand is going to increase, but probably not too dramatically nor too quickly imho.

And that's without considering home generated energy and time shifting loads that will level out grid demand somewhat.

[AGT]

These diversity equations were before heat pumps and EV’s were the norm.

I imagine new equations and some serious investment in infrastructure will be required for the future!

[Oldgreybeard]

These diversity equations were before heat pumps and EV’s were the norm.

I imagine new equations and some serious investment in infrastructure will be required for the future!

The choice is either to spends hundreds of millions on new/upgraded infrastructure, or just fit cheap load limiters to every home in place of the main fuse and just make the high demand customers pay a much higher standing charge, as they do in France.

Ideally we'd have the infrastructure improvements, but given that fitting something like the French option will be a fraction of the cost, which seems most likely?

Edited to add:

Some rough sums. Say 50% of the transformers need doubling in power to meet the needs of 50% of UK homes needing a lot more power. A 100kVA transformer is around £20k, plus installation, so say £25k each installed (ignoring the cable upgrade cost). If 50% of the existing 11kV to LV transformers were upgraded that's a bit over £12 billion.

The other option is fitting a £30 limiter to every home, at a cost of maybe £60 per home (it's no more than a ten minute job). Say 30 million homes in the UK, so to fit one to 50% of UK homes to control demand is going to cost about £900 million.

I rather suspect that £900 million will look like a more attractive option than the rather conservative £12 billion, it would be a lot quicker to rollout and it would earn additional revenue, which the transformer upgrades wouldn't.

[Stinsy]

I’m not so sure this is the problem everyone is making it out to be. The problem is “peak” power usage. BEVs aren’t charged then, HPs don’t add much to peak demand, other appliances (particularly lighting) have gotten much more efficient over the years. Micro-generation too reduces the strain on infrastructure.

[smegal]

I’m not so sure this is the problem everyone is making it out to be. The problem is “peak” power usage. BEVs aren’t charged then, HPs don’t add much to peak demand, other appliances (particularly lighting) have gotten much more efficient over the years. Micro-generation too reduces the strain on infrastructure.

I agree. Also, the new randomised starting time for all post July 2022 EV chargers will help.

I think the concerns that some have about lots of people jumping on ToU tarrifs making a surge if demand say between midnight and four is unlikely to be a huge issue as well.

[Oldgreybeard]

I’m not so sure this is the problem everyone is making it out to be. The problem is “peak” power usage. BEVs aren’t charged then, HPs don’t add much to peak demand, other appliances (particularly lighting) have gotten much more efficient over the years. Micro-generation too reduces the strain on infrastructure.

The real problem is not going to be peak use, it's going to be off-peak use, unless off-peak prices increase a lot.

The network capacity problem isn't with generation, or high voltage distribution, if you look ant the capacity maps some DNOs produce the problem is almost entirely the low voltage thermal one, mostly at low voltage transformers and some of the LV cables from them out to the points where individual cables run to homes. The cables into homes aren't an issue, they seem able to handle the increase in current in the main.

Pricing is driving some to maximise the current they draw overnight, especially those with EVs and home batteries. Some suppliers are actively encouraging this, as they can make a slightly greater margin on selling cheap rate electricity and also because it takes away some peak demand and so reduces the price they pay above the OFGEM cap (suppliers can, at times, lose money on peak rate sales at the moment).

The DNOs are completely divorced from the suppliers (by law) so have no way to influence suppliers to not encourage more demand during times when the generators have a surfeit, usually at night. The issue is where power runs. Domestic usage is traditionally low during the middle of the day, higher in the late afternoon and early evening, and low overnight. Industrial and business usage is high during the middle of the day and low in the evening and overnight.

What we are likely to see in future is a pattern of use like mine. We use close to zero grid power from 6:30 in the morning until 11:30 at night, then I pull the entire energy needed to heat the house and hot water, run it for the following day (by charging the house batteries) and charge the car. It's very rare for me to draw less than about 6kW for a few hours each night in winter, not unusual for me to draw over 14kW for an hour or two some nights.

The DNO assumption seem to be that I will draw just a few kW, perhaps only around 3kW or so for any period of time, judging from the size of their transformers. We know that more people are buying home batteries - the price has rocketed and availability has decreased over the past year. We know that people are switching from oil and gas to heat pumps. We also know that EVs are becoming more popular.

We also know that suppliers are encouraging new customers with tariffs that offer cheap electricity for overnight periods. We've seen from the way some of us here on the forum are changing their usage patterns (me included) that the present pricing structure makes it attractive to pull as much of your daily energy needs as possible during the short off-peak window.

The DNOs never designed their domestic low voltage networks to cope with this pattern. They designed them to cope with the traditional domestic evening surge pattern, a period of short duration overloads as cookers and kettles turn on and off and appliances get used. Cables and transformers are mostly thermally limited, so can probably cope with a pretty high overload for short periods, say the 10 minutes it takes and oven or hob to get up to temperature, or the five to ten minutes a washing machine or dishwasher pulls maximum power to heat water.

If more people do as I'm doing, then the domestic low voltage network is going to see sustained overnight overloads for hours, rather than tens of minutes. From the document linked to earlier it just doesn't look as if the domestic low voltage distribution system has been designed to deal with this. I doubt there's an issue with non-domestic LV transformers and cabling, as the pattern of use for them isn't likely to change much, and demand for those LV networks is usually lower over night.

[Stinsy]

I’m not so sure this is the problem everyone is making it out to be. The problem is “peak” power usage. BEVs aren’t charged then, HPs don’t add much to peak demand, other appliances (particularly lighting) have gotten much more efficient over the years. Micro-generation too reduces the strain on infrastructure.

The real problem is not going to be peak use, it's going to be off-peak use, unless off-peak prices increase a lot.

The network capacity problem isn't with generation, or high voltage distribution, if you look ant the capacity maps some DNOs produce the problem is almost entirely the low voltage thermal one, mostly at low voltage transformers and some of the LV cables from them out to the points where individual cables run to homes. The cables into homes aren't an issue, they seem able to handle the increase in current in the main.

Pricing is driving some to maximise the current they draw overnight, especially those with EVs and home batteries. Some suppliers are actively encouraging this, as they can make a slightly greater margin on selling cheap rate electricity and also because it takes away some peak demand and so reduces the price they pay above the OFGEM cap (suppliers can, at times, lose money on peak rate sales at the moment).

The DNOs are completely divorced from the suppliers (by law) so have no way to influence suppliers to not encourage more demand during times when the generators have a surfeit, usually at night. The issue is where power runs. Domestic usage is traditionally low during the middle of the day, higher in the late afternoon and early evening, and low overnight. Industrial and business usage is high during the middle of the day and low in the evening and overnight.

What we are likely to see in future is a pattern of use like mine. We use close to zero grid power from 6:30 in the morning until 11:30 at night, then I pull the entire energy needed to heat the house and hot water, run it for the following day (by charging the house batteries) and charge the car. It's very rare for me to draw less than about 6kW for a few hours each night in winter, not unusual for me to draw over 14kW for an hour or two some nights.

The DNO assumption seem to be that I will draw just a few kW, perhaps only around 3kW or so for any period of time, judging from the size of their transformers. We know that more people are buying home batteries - the price has rocketed and availability has decreased over the past year. We know that people are switching from oil and gas to heat pumps. We also know that EVs are becoming more popular.

We also know that suppliers are encouraging new customers with tariffs that offer cheap electricity for overnight periods. We've seen from the way some of us here on the forum are changing their usage patterns (me included) that the present pricing structure makes it attractive to pull as much of your daily energy needs as possible during the short off-peak window.

The DNOs never designed their low voltage networks to cope with this pattern. They designed them to cope with the traditional domestic evening surge pattern, a period of short duration overloads as cookers and kettles turn on and off and appliances get used. Cables and transformers are mostly thermally limited, so can probably cope with a pretty high overload for short periods, say the 10 minutes it takes and oven or hob to get up to temperature, or the five to ten minutes a washing machine or dishwasher pulls maximum power to heat water.

If more people do as I'm doing, then the low voltage network is going to see sustained overnight overloads for hours, rather than tens of minutes. From the document linked to earlier it just doesn't look as if the domestic low voltage distribution system has been designed to deal with this.

I’m not so sure about that. Plenty of houses had storage heaters 50 years ago so would draw 10kW or more for hours on end. The LV grid coped with that so a HP and BEV will be no trouble.

[Oldgreybeard]

I’m not so sure about that. Plenty of houses had storage heaters 50 years ago so would draw 10kW or more for hours on end. The LV grid coped with that so a HP and BEV will be no trouble.

Sadly some DNOs took the opportunity to downsize and rip out a lot of the old storage heating capacity, to save money when equipment came up for replacement. An example was their switch from overhead singles to aerial bundled cable, due to the constant repairs needed to singles from storm damage (like the dancing cable problem in high winds). ABC is more expensive, but more reliable, so to reduce the cost differential they've tended to downsize the newer cables, as there is no longer a need to run storage heating loads.

Our village is a typical example. Storage heaters were popular in the 1960's and the transformers and cabling were all uprated by the electricity board to cope with them. What we've seen since privatisation is cabling and transformer sizes being reduced when replacement comes around, because storage heating has gone out of fashion since around the late 1970's. Pretty much every new housing development built in the past 40 years won't have the electricity supply capacity to run storage heaters, and there are thousands of housing developments like that now. The example quoted earlier shows this - they now plan on just a few kW per house, rather than 10kW to 15kW per house during the storage heating period.

Edited to add:

Just remembered the DNO completely removed one ground mounted transformer when they replaced the cables in the village with ABC. The concrete pad is still there, but they now feed the whole village from the two pole mounted transformers, both pretty old, one at either end. At a guess that's just about halved the village transformer capacity, and was done not long before we started to build this house, as I remember driving past the orange barriers they put up whilst they were taking it out, so around ten to twelve years ago at a guess. Seems short-sighted, but at least the concrete pad is still there at the side of the lane, so they could probably put it back.

[Stinsy]

I’m not so sure about that. Plenty of houses had storage heaters 50 years ago so would draw 10kW or more for hours on end. The LV grid coped with that so a HP and BEV will be no trouble.

Sadly some DNOs took the opportunity to downsize and rip out a lot of the old storage heating capacity, to save money when equipment came up for replacement. An example was their switch from overhead singles to aerial bundled cable, due to the constant repairs needed to singles from storm damage (like the dancing cable problem in high winds). ABC is more expensive, but more reliable, so to reduce the cost differential they've tended to downsize the newer cables, as there is no longer a need to run storage heating loads.

Our village is a typical example. Storage heaters were popular in the 1960's and the transformers and cabling were all uprated by the electricity board to cope with them. What we've seen since privatisation is cabling and transformer sizes being reduced when replacement comes around, because storage heating has gone out of fashion since around the late 1970's. Pretty much every new housing development built in the past 40 years won't have the electricity supply capacity to run storage heaters, and there are thousands of housing developments like that now. The example quoted earlier shows this - they now plan on just a few kW per house, rather than 10kW to 15kW per house during the storage heating period.

Edited to add:

Just remembered the DNO completely removed one ground mounted transformer when they replaced the cables in the village with ABC. The concrete pad is still there, but they now feed the whole village from the two pole mounted transformers, both pretty old, one at either end. At a guess that's just about halved the village transformer capacity, and was done not long before we started to build this house, as I remember driving past the orange barriers they put up whilst they were taking it out, so around ten to twelve years ago at a guess. Seems short-sighted, but at least the concrete pad is still there at the side of the lane, so they could probably put it back.

Again that contradicts what I’m reading. I’d be i interested if you could provide a source. I read an article the other day where that particular DNO had moved from 13.8kVA per dwelling to 15kVA a few years back and was now moving to 20kVA per dwelling for new developments.

[Oldgreybeard]

Again that contradicts what I’m reading. I’d be i interested if you could provide a source. I read an article the other day where that particular DNO had moved from 13.8kVA per dwelling to 15kVA a few years back and was now moving to 20kVA per dwelling for new developments.

The key seems to be in the examples in the linked document from earlier. Quoting from one example they give for diversity allowances for a new housing development:

Demand estimator example for 80 houses.jpg (91.62 KiB) Viewed 3222 times

ADMD in this example stands for After Diversity Maximum Demand. The reference to diversity is the normal assumption used for all electrical installations that not all high power appliances may be drawing power at the same time (used to be true, but not so much now with off-peak rates and loads like EVs and home batteries).

That example assumes that the weighted average ADMD for such a housing development would be only 3.5kW per house. That same document also states that the capacity of the cable to each home shall be 20kVA, which I think makes no allowance for ADMD, it's just safe cable sizing, and is why I don't think there is an issue with cabling into most homes, only an issue with the transformer and perhaps part of the LV distribution cable sizing:

Power per home.jpg (135.19 KiB) Viewed 3216 times

Clearly, in the longer term there must be either a need to increase these example ADMD numbers to reflect electric heating, car charging, home batteries etc, or a means to control demand at each home, but I doubt that this will happen quickly, and will lay money that what are seen as easier fixes will be rolled out at first, like load limiting or load scheduling (as is already happening with smart EV chargers, I believe).

We're going to see some friends on New Years Day that live on an estate built around 30 years ago. If I get time, I'll wander around and see if I can count the houses and check the transformer rating. My instinctive feeling is that the cabling to the individual houses will be fine for 20kVA, the issue is almost certainly the transformer rating and the cabling from the transformer before it splits out to the cables to each house. I also doubt that the high voltage cabling will be an issue, as the current is tiny, just 9A in total for 11kV cables supplying a 100kVA transformer (so about 3A per conductor).


Edited to add:

if the 80 house development in the example above was made up of all-electric homes like ours, then during the winter months they would need to increase the weighted average ADMD from 3.5 kW to around 11kW to 12kW per home. That would increase the transformer requirement from 288kVA to between 880kVA and 960kVA, a pretty substantial upgrade, especially as I would imagine a fair bit of the distribution wiring would also have to be upgraded as well.