But the thing is is that the bulk of the cost to install a QC are one-offs related to trenching and labor. To add a 2nd QC the cost is just hardware, or about $15k for the Nissan QC. So even if you just install two QC stations, now your cost goes up 15-30%, but you get two stations and can push 4-5 times the number of charges per day while maintaining the same service quality.RegGuheert said:You are certainly correct on all points. But I can also see the logic behind a business decision which says "It's not worth spending another $50,000 to $100,000 to add a second QC when the first one is used less than 5X daily." (...or whatever the number is.) It really is a chicken and egg problem for charging vendors. They cannot subsidize their quick chargers by selling cars like Tesla does.
Capacity of Charging Stations Using an Erlang-B Model
The numbers in that thread assumes only a 2% blocking rate which is a very good service rate. Bump that up to 10% (the amount of times you'll get there and have to wait) and the throughput looks like this:
1 station: 0.1 charges / hour
2 stations: 0.55 charges / hour
3 stations: 1.25 charges / hour
4 stations: 2.0 charges / hour
Look at how many charges / hour you can support by going to a 2nd station while maintaining a 10% chance of finding all stations busy.
Let's say you want to support 5 charges daily before you expand. You probably only have about 12 hours a day where people are going to use the station. Basically once you get to 5 charges/day you are overloaded and people are going to be waiting frequently which provides bad service. And now you have to double your infrastructure cost.
Just look at the EV Project infrastructure reports. http://www.theevproject.com/documents.php" onclick="window.open(this.href);return false;
On the last report, across all regions DC QC stations already have a vehicle connected 5% of the time. Then you factor in that most of the use occurs from 8am-8pm. Then you look at the median usage rate and you find that it's already at 10% with peaks approaching 20%.
If you know you have a 10-20% chance of having to wait up to 30 minutes to charge - how likely satisfied are you going to be with that experience? Not to mention that you know that there will be some stations pushing much higher utilization rates than that, there are quite a few stations that are operating well over an ideal capacity. Just look at the SF Bay Area section - there the median usage rate is 10-20% from 6:30-7:30 with the peak over 40%. Crazy!
FWIW, the average charging time is 20 minutes and delivers 8 kWh.