POCO "Load Diversity" & EV Charging

[augie47]

Question for some of you familiar with sizing POCO equipment.
This thread, https://forums.mikeholt.com/threads/ev-charger-load-shedding-device.2561923/ , made me wonder.
All of us see where POCOs are able to downsize their transformers and service conductors based on years of input on load diversity.
As EVs become more popular and devices like the one in the referenced thread begin being installed it would seem that the old rules might not apply. Now with multiple dwelling units with EV chargers on a transformer it would seem it might have an adverse effect on POCOs equipment sizing based on previous load diversity.
Has anyone seen a change ???

 

[retirede]

One thing to consider is that most people charge overnight when their normal demand is lowest.

 

[petersonra]

One thing to consider is that most people charge overnight when their normal demand is lowest.

Another thing to consider is that the current requirements of many of these chargers equal or exceed the normal maximum currents the dwelling would otherwise use. If EV takes off in a serious way, the era of cheap surplus electricity at night will go away, likely requiring utilities to add generating capacity.

And what good will smart meters be when there are few times during the day when there is cheap electricity available?

 

[don_resqcapt19]

Unless the grid is completely redone to support a large number of EVs, the only way this will work is if the utility has control of the chargers so they can limit the load on the distribution system in the area.

Some utilities have said a 15 to 20% penetration of EVs in their residential areas has the potential of tripping the distribution breakers, of they cannot control the chargers.

Some utilities even want interactive chargers so that in times of peak loads, they can take power out of your EV to support the grid.

 

[retirede]

Another thing to consider is that the current requirements of many of these chargers equal or exceed the normal maximum currents the dwelling would otherwise use. If EV takes off in a serious way, the era of cheap surplus electricity at night will go away, likely requiring utilities to add generating capacity.

And what good will smart meters be when there are few times during the day when there is cheap electricity available?

I disagree with “many”. Some Teslas may get close, but the largest SAE J1772 (all but Tesla) EVSE is 48A continuous. Most are smaller, 32A.

 

[winnie]

While a very common home will have 200A service, but the normal current drawn will be less than that by a long shot.

My home has a 100A service. My average power usage is less than 1 kWh per hour, so on average I am using less than 4A. I don't know what my peak usage is but I'd be surprised if it exceeds 40A.

A charger drawing 32A would exceed the bulk of my usage by a long shot.

My normal driving is perhaps 200 miles per week. This would be about 50kWh, or a large chunk of my energy usage, but would not exceed the rest of my use.

-Jon

 

[petersonra]

I disagree with “many”. Some Teslas may get close, but the largest SAE J1772 (all but Tesla) EVSE is 48A continuous. Most are smaller, 32A.

How many people use even 32 Amps at night? Or during the day for that matter. Most people live in tiny apartments or condos and the amount of electricity they use is not that much. 32 Amps is about 7 kW. That is a lot of load unless you have electric heat or the A/C is running.

My guess would be most people are using no more than 20 kW-hr per day in total. That's only 3 hours of charging.

 

[electrofelon]

It is an interesting issue. I do wonder though is this any different from electric load increases in the past? Wasn't electric service just for lighting in the beginning? Weren't things like power tools l, electric heat, and air conditioning not originally planned for? Or just suburbs that have exploded in the past or even the last few decades for that matter. I think even without EV's we are heading toward a situation where we need a smarter Grid with more load control. This is an interesting quandary as generally Americans are used to using as much as they want whenever they want.

 

[hillbilly1]

One thing to consider is that most people charge overnight when their normal demand is lowest.

That’s what they say, logically though, the demand is not that much lower. A/C’s are still running in southern areas, which would be a larger total load than cooking. Sure, plants that run only one shift would be shutdown, but office buildings would still have a substantial A/C load still on. Lighting may be off, but with the advent of LED lighting, that load would substantially be lower than heating and cooling. EV charging would be a larger sustained load than residential day time needs. Other than industrial loads, I would believe total residential loads would actually be higher at night than during the day. Total load on the grid though may balance out a little better with non-24 industrial figured in.

 

[electrofelon]

That’s what they say, logically though, the demand is not that much lower. A/C’s are still running in southern areas, which would be a larger total load than cooking. Sure, plants that run only one shift would be shutdown, but office buildings would still have a substantial A/C load still on. Lighting may be off, but with the advent of LED lighting, that load would substantially be lower than heating and cooling. EV charging would be a larger sustained load than residential day time needs. Other than industrial loads, I would believe total residential loads would actually be higher at night than during the day. Total load on the grid though may balance out a little better with non-24 industrial figured in.

I always heard the quick and dirty figure that 1/3 is residential, 1/3 is commercial, and 1/3 is industrial. I would think there is enough power at night for EV's due to most industrial and commercial being off, but I could see distribution and subtransmission needing to be beefed up.

 

[winnie]

I heard an interesting suggestion about the utility controlled 'smart thermostats'.

The suggestion was that since the utility can reasonably forecast peak usage, rather than shutting off people's air conditioning at peak times, they should pre-cool homes so that the thermostat doesn't call for cooling at peak times.

A similar approach would work for EVs if the utility could guarantee that sometime overnight you would get the charge you need for the next day, even if you don't know exactly when it would happen.

Jon

 

[gadfly56]

I always heard the quick and dirty figure that 1/3 is residential, 1/3 is commercial, and 1/3 is industrial. I would think there is enough power at night for EV's due to most industrial and commercial being off, but I could see distribution and subtransmission needing to be beefed up.

You are correct, I think you can confirm this at the IEA web site.

You might have enough juice, but you're right, it's the distribution system that's the issue. It's sized to that 1/3 portion and no or very little more.

 

[retirede]

My guess would be most people are using no more than 20 kW-hr per day in total. That's only 3 hours of charging.

I guess I’m not most people. My lowest usage is spring/fall in between heating and cooling seasons. I’ve never been below 1200 KWH (40 per day). In the summer, I’ll hit 3000 (100 per day). Charging my car adds about 100-150 KWH per month, hardly noticeable.