hmmm - as I always suspected - the grid can handle EV's

daveo4EV

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https://www.yahoo.com/news/fact-check-electric-vehicles-put-093308278.html

Concerns that electric vehicles could damage the grid, he emphasized, are misplaced.

it would still make up only 1.5% of the power grid's capacity.
I've always felt/believed/analyzed the following…
  1. if you're saying the grid can't handle EV's - you're saying it can't handle electric appliances - since a home EVSE is really no different than a electric appliance
  2. refining gasoline is one of the _MOST_ electricity intensive things we do as a society - it takes 6 kWh per-gallon of refined gasoline
    1. as you consume less gasoline you free up existing grid capacity
  3. even as EV's eventually 'stress' the grid over time upgrading/improving the grid is not a bad thing and probably necessary anyways - if anyone thinks the grid is static, and not going to evolve then that is unrealistic in my opinion - it's a net good thing to improve the grid and benefits all of society and is necessary with or without EV's in the picture.
but those are my biases and beliefs - but the article was interesting to me personally

 

JimBob

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I think this depends on your local grid. Totally in agreement that the grid (everywhere needs to be strengthened). EV's are not a threat now as they are generally charged overnight when electricity demand is less. The power company loves this as it generates revenue in a normally quiet period. Maximum electricity demand is generally between about 11am and 7pm, at least in my area. If your area is already at risk of brownouts in the summer, read southwest America, plugging in huge numbers of EV's during peak demand isn't going to help.

It should also be asked as to how electricity is generated in your area. In my province of Ontario 92.5% of electricity is generated from nuclear, water, wind and solar. In carbon rich Alberta, 10% of electricity is generated from wind and hydro. Sorry Alberta Taycan owners, but you're part of the problem.

Now I will dismount from my high horse.
 

Windpower

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The beauty of EV charging is that most of it can be done at night, off peak. Power authorities need to built plants to handle the peak power load, but EVs which charge at night don't increase the peak power load. Therefore, EVs which charge off peak would not increase the size of the power plant needing to service an area.

Plus, as Dave pointed out above, the power to charge an EV is the same as a home electric oven or a home electric dryer (240v at 40 amps). But while you normally cook during peak or near peak and the power company needs to take electric ovens and dryers into consideration when planning the size of power plants, EVs can be charged in the middle of the night so they don't add to the peak power consumption calculation.
 

Klepper

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The beauty of EV charging is that most of it can be done at night, off peak. Power authorities need to built plants to handle the peak power load, but EVs which charge at night don't increase the peak power load. Therefore, EVs which charge off peak would not increase the size of the power plant needing to service an area.

Plus, as Dave pointed out above, the power to charge an EV is the same as a home electric oven or a home electric dryer (240v at 40 amps). But while you normally cook during peak or near peak and the power company needs to take electric ovens and dryers into consideration when planning the size of power plants, EVs can be charged in the middle of the night so they don't add to the peak power consumption calculation.
Great post!
 

Midlifecrisis

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The beauty of EV charging is that most of it can be done at night, off peak. Power authorities need to built plants to handle the peak power load, but EVs which charge at night don't increase the peak power load. Therefore, EVs which charge off peak would not increase the size of the power plant needing to service an area.

Plus, as Dave pointed out above, the power to charge an EV is the same as a home electric oven or a home electric dryer (240v at 40 amps). But while you normally cook during peak or near peak and the power company needs to take electric ovens and dryers into consideration when planning the size of power plants, EVs can be charged in the middle of the night so they don't add to the peak power consumption calculation.
You must have a very big electric dryer!! My car pulls 7kW from the charger, the dryer is about 1.5-2kW. Nowhere near the car. I struggle to get our smart meter showing over about 5kW unless the car is charging. And even then it goes up and down as the element in the oven/hob/etc. turns on and off. The key is to get EVs charging out of peak times unless absolutely necessary. Then there will be no problems
 


Windpower

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You must have a very big electric dryer!!
I have a Samsung electric dryer. The circuit is 240v with a 40 amp circuit breaker and a 14-50 socket behind the dryer. I just checked the specs and the dryer needs 15 amps at 240v.
 

Midlifecrisis

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I have a Samsung electric dryer. The circuit is 240v with a 40 amp circuit breaker and a 14-50 socket behind the dryer. I just checked the specs and the dryer needs 15 amps at 240v.
So still only about half the power an EV takes when using the maximum amount and it will fluctuate as the thermostat turns the heater on and off. But that is still a much bigger dryer than most people will have - every home dryer in the UK will plug into a 13A socket and probably use less than 10A at 240V. So no more than 2.4kW
 
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daveo4EV

daveo4EV

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You must have a very big electric dryer!! My car pulls 7kW from the charger, the dryer is about 1.5-2kW. Nowhere near the car. I struggle to get our smart meter showing over about 5kW unless the car is charging. And even then it goes up and down as the element in the oven/hob/etc. turns on and off. The key is to get EVs charging out of peak times unless absolutely necessary. Then there will be no problems
electrical dryers "pulse" the heating element - they don't use 20/30/40 amps continuously - they turn the heating element "on" and then "off" - you have to catch them "in the act" to see their max usage…

my electric dryer can use 6 kW total on it's 30 amp circuit - but never for very long - but on/off/on/off/on/off on a rhythm…

there are very very few appliances that are like an EVSE - which will just flat line at "full" amps with no break - until they are done, when they just stop…

this is why EVSE's only get to use 80% of the rated breaker load - they are considered continuous use devices (appropriately so) so they only get 80% of the rated breaker load to play with.

240v * 50 amps = 12,000 watts or 12 kW

but 80% rule

80% of 50 amps = 40 amps

240v * 40 amps = 9,600 watts or 9.6 kW

that's what a 50 amp breaker can do for EV charging cause it can run at a full 9.6 kW for 8+ hours if the battery is mostly empty…and if watch the charging curve it is _FLAT_ until it turns off - no pulsing like a electric dryer or other electrical home appliance.
 
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daveo4EV

daveo4EV

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here is the power draw graph from charging my Cayenne the other day - nearly 2 hours solid "flat" line at a full 7.x kW - no other home appliance behaves like this…the taper at the end is when the battery is close to full so the amps are backed "off" to gently land the battery at 100% for longevity.

for the mathematically/engineering inclined the two axes of the graph are "kw" and time - at any given moment this graph shows we're close to 7.2 kW - the area under the curve is kWh (kilowatt-hours) - the summary at the top nicely illustrates the area under this curve is 13.4 kWh of billed electricity usage - my off peak rate is about $0.08/kWh - so this charging session cost me $1.07

the Cayenne will go about 25 miles on average for a full charge - so per-mile cost is $0.04/mile

vs. the Cayenne hybrid's gasoline motor efficiency of about 22 mpg - and gas today in Aptos, CA is about $6.89/gallon - so running the Cayenne's gas motor is about $0.31/mile - I'm loving the all EV hybrid and my Taycan right now.

Screen Shot 2022-07-12 at 3.17.06 PM.png
 
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David Bennett

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electrical dryers "pulse" the heating element - they don't use 20/30/40 amps continuously - they turn the heating element "on" and then "off" - you have to catch them "in the act" to see their max usage…

my electric dryer can use 6 kW total on it's 30 amp circuit - but never for very long - but on/off/on/off/on/off on a rhythm…

there are very very few appliances that are like an EVSE - which will just flat line at "full" amps with no break - until they are done, when they just stop…

this is why EVSE's only get to use 80% of the rated breaker load - they are considered continuous use devices (appropriately so) so they only get 80% of the rated breaker load to play with.

240v * 50 amps = 12,000 watts or 12 kW

but 80% rule

80% of 50 amps = 40 amps

240v * 40 amps = 9,600 watts or 9.6 kW

that's what a 50 amp breaker can do for EV charging cause it can run at a full 9.6 kW for 8+ hours if the battery is mostly empty…and if watch the charging curve it is _FLAT_ until it turns off - no pulsing like a electric dryer or other electrical home appliance.
It's interesting how local regulations / habits can impact how equipment is installed. All breakers are designed to carry their rated current on a permanent basis so this de rating to 80% isn't really required. Perhaps the fact that the 50A normally costs more than the 40A so the installer can make a bit more is also at play?
 

JimBob

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Perhaps the fact that the 50A normally costs more than the 40A so the installer can make a bit more is also at play?
This is not what its about. It's all about safety. To loosely interpret the NEC code, the code considers that overcurrent protection may be affected by heat in the system. It uses the concept of continuous load and non continuous load. Continuous load is where the maximum current is expected to run for at least 3 hours. You can use the breaker at its full capacity if it is not continuous current. If it is continuous, then you need to use the 80% limitation. There are breakers that are listed for 100% operation, but they have additional requirements for installation that need to be met. Simpler to just use the 80% rule and not worry about the fine points. If you want to save some money, get the breaker listed for 100% and follow the rules.

Pretty clear that an EV charger would be considered a continuous load.
 

nickmdp

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I would add the caveat that the quote about 1.5% of the power grid's capacity was a bit more nuanced:

Even if all 4,000 EVs in Kentucky charged using LG&E's grid on the same day, which is incredibly unrealistic, it would still make up only 1.5% of the power grid's capacity.
In a state of over 4 million people, it's easy to imagine a 100x increase or more in the number of EVs, which would obviously cause a bigger problem, and I assume they actually mean at the exact same time and not just the same day, since many cars will charge on a more or less daily routine I imagine.

Anyways, all the evidence you need that moving to EVs won't ruin the grid is that electric companies are offering incentives to customers to buy EVs and EVSEs. They're almost always monopolies in the US as far as I'm aware of, where a home has no options to get a different electric provider, so the utility has no incentive to offer this as a way of enticing customers to switch to their service.

The only reason a utility has to offer a program that gives money back to customers is because they think it will help them save money in the long term. If they were worried that EVs were being adopted too quickly, they would surely be removing those incentives and trying to find some way to start charging EV owners more.
 

David Bennett

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This is not what its about. It's all about safety. To loosely interpret the NEC code, the code considers that overcurrent protection may be affected by heat in the system. It uses the concept of continuous load and non continuous load. Continuous load is where the maximum current is expected to run for at least 3 hours. You can use the breaker at its full capacity if it is not continuous current. If it is continuous, then you need to use the 80% limitation. There are breakers that are listed for 100% operation, but they have additional requirements for installation that need to be met. Simpler to just use the 80% rule and not worry about the fine points. If you want to save some money, get the breaker listed for 100% and follow the rules.

Pretty clear that an EV charger would be considered a continuous load.
That's why I said it was interesting how different practices exist.

Breakers designed to IEC60898 or the NEMA / ANSI equivalent are rated to run continuously at their nominal current. The local installation codes are asking you to de rate, here in UK that is not the case in any standard, code or by habit unless you had a high density of breakers close proximity. De rating of the kind you mention would usually only be applied to cables, depending on their installation method, Using a 50A when a 40A would suffice would be considered poor practice since the thermal cable projection is reduced or you would have to oversize the cable.

My 7KW charger was installed by my utility company with a 32A breaker with no issues whatsoever.
 

Midlifecrisis

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That's why I said it was interesting how different practices exist.

Breakers designed to IEC60898 or the NEMA / ANSI equivalent are rated to run continuously at their nominal current. The local installation codes are asking you to de rate, here in UK that is not the case in any standard, code or by habit unless you had a high density of breakers close proximity. De rating of the kind you mention would usually only be applied to cables, depending on their installation method, Using a 50A when a 40A would suffice would be considered poor practice since the thermal cable projection is reduced or you would have to oversize the cable.

My 7KW charger was installed by my utility company with a 32A breaker with no issues whatsoever.
Interesting. My breaker is 40A. The man who did the survey in advance of fitting told me that sometimes the current can go up as high as 38A as the car comes off charge or at some point of the charge process. I didn’t really understand why that would be and if your 32A circuit has never tripped then maybe he was wrong. But 32A is a pretty fine margin on a 7.1kW EVSE
 

 
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