. . . Some may ask why onsite energy storage is necessary for EV charging, and the simple answer is demand charges. Demand charges are based on the highest draw the customer (in this case all the charging stations at one location) uses from the utility during a set period of time in a given month, usually carved up into 15-minute intervals.
Demand charges vary from utility to utility in the US, but they are so costly they make it nearly impossible for DC Fast charge stations to even break even, let alone be profitable. For example, I own and manage a 24 kW DC fast charger on my property in Montclair, NJ. I pay 12 cents per kWh for my electricity supply, but because the DC Fast charger pulls so much energy at once, I have to pay demand charges for it, pushing the cost of my electricity up well over $1.00 per kWh. . . .
The reason we haven’t seen widespread use of battery storage with EV charging sites has been the upfront cost. Network providers have done the math, and it was less expensive to just pay the demand charges, than it would have been to spend $50,000 to $100,000 for the onsite battery storage systems. Hopefully, this announcement means the cost is finally getting down to the point where it is becoming financially viable.
Each Electrify America site in this program will consist of a 210 kW battery system, with roughly 350 kWh of capacity. They have a modular design, and will allow for more capacity to be added over time. That will become necessary, once there are multiple EVs plugging in and pulling 150+ kW at the same location. . . .