EV Charging Station Demand Factors

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Mr. Pickle

Mr. Pickle

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Rogers MN
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Electrical
Has anyone determined what demand factors would apply for multiple electric vehicle charging stations?

i.e. a multifamily project with 110 EV chargers. When calculating the loads, are these to be included at 100% or can a demand factor be applied when sizing for the distribution and/or service?

I understand 624.41 requires OCP of 125%, but I haven't found where the NEC addresses demand factors for load calculations.
 
I doubt there is any demand factor allowance since there is a very good chance that all or most of them would be charging at the same time in the evening when people get home from work.
 
By “110 EV chargers” do you mean a level 1 (120V) EVSE? If so, every one I’m familiar with is cord and plug standard NEMA 5-15.
Is 120V cord & plug equipment normally included in a load calc or is it just part of the general receptacle load?
These things are “only” 1440 watts (12A) max.

Edit….maybe 110 is the quantity? That’s a different story, if they’re level 2.
 
The following was added to 625.42 in the 2020 code along with language permitting the rating to be based on a restricted access setting within the charging equipment.
Service and feeder shall be sized in accordance with the product ratings.
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There is no provision for any type of demand factor in that section, so it appears that you need to include the sum of the ratings in your service and feeder load.
 
don_resqcapt19 said:
The following was added to 625.42 in the 2020 code along with language permitting the rating to be based on a restricted access setting within the charging equipment.

There is no provision for any type of demand factor in that section, so it appears that you need to include the sum of the ratings in your service and feeder load.
Click to expand...
You might be able to run the conduit and wire but not hook it up so there is no way to actually use them and provide for a handful to be used in your load calculation. Chances are only a handful will ever be used anyway.

Down the road you will have data to show the actual usage and can hook up as many additional ones as that data would allow.
 
Our clients are using chargers that are wifi-connected. They monitor the total load in real time and throttle the chargers to stay under a given setpoint. That way, you can put ten 40A chargers on a 200A panel. If only 4 are running, they all get 40 amps. When the 5th one comes on, they all back off and only draw 32 amps. If all 10 are on they would get 16 amps each.
 
JoeStillman said:
Our clients are using chargers that are wifi-connected. They monitor the total load in real time and throttle the chargers to stay under a given setpoint. That way, you can put ten 40A chargers on a 200A panel. If only 4 are running, they all get 40 amps. When the 5th one comes on, they all back off and only draw 32 amps. If all 10 are on they would get 16 amps each.
Click to expand...
so if they are all on the same panel, how does the electricity used get charged back to the actual user?
 
I have no direct experience, but presumably this same system could work across many meters in something like an apartment building.

Each unit has say a 100A service which includes a 50A circuit for their charger. The full 50A is part of the calculation for the apartment feeder conductors.

The chargers would be interlinked by wifi for a given maximum total current, and this maximum aggregate load is what gets used for the over-all building calculation.

As I read 625.42 if the system is listed for limiting the maximum aggregate load, the programmed maximum is the load you use in your calculation.

Jon

Jon
 
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