Demand Charges and EV Charging Costs
There are public charging stations at UCLA and in Santa Barbara that charge $2.00 per hour. That is the base billing rate on the Blink network. It takes 4 hours to charge a Volt fully. That would put the price of a charge at $8.00 for 35 to 45 miles. That is as bad as paying $8.00 per gallon for gasoline. What would that do to EV adoption?
There is even a valid case for charging more than that up to $5.00 per hour! What is more, the reasons behind this will make the situation even less tenable when it comes to using DC to DC fast charging.
The cost of charging the battery pack on a Volt is about $1.30 on normal home charging. That will let the car go between 35 and 48 miles. Saving the cost of fuel like that is basic to the cost/benefit of driving an EV that makes sense to a typical consumer. But what if public charging cost four or five times that?
The links immediately above will take you to more details.
It is bad enough that this could be true for public charging but the same or a similar problem may apply to apartments and condos as well as to work place charging. That is a subject for a future article.
These challenges point the way to solutions and the need to consider these concerns more carefully. There were a few solutions that came out of discussions at EVS that help make this work. The next newsletter will go into some of the ways to handle these concerns.
There are two significant reasons behind justifying these high rates for charging. One is to do with the fees and carrying costs of operating the chargers. These will be discussed in another future article. The other reason is the whole concern about demand charges.
Demand charges are the first big issue that needs to be handled as it is basic to where chargers are sited. These charges apply to big commercial users of electricity like parking garages and mid-sized businesses. They start to become relevant to meters that use over 20 kilowatts (kW) at any given time.
The reason that the electric utilities have to use these charges is because it costs money to make sure that there is enough electricity available to meet the demand. The utilities have to have enough electricity (kW) coming from the wires or the quality (meaning the Voltage) will drop. That is easy when the demand is consistent but harder if the demand goes up and down a lot. The demand charges cover what the utilities have to do to meet the peak demand for any and all customers.
The utility companies have demand meters that are installed with all customers that have over a certain demand level for electricity, which in the case of Southern California Edison is 20 kW at any given time. The demand meters are called fifteen minute meters because the meters capture discrete 15-minute intervals of energy use. The meter is reset when it is read.
Jim Dewey from the City of Santa Barbara is helping us get clear about how all this works. He describes the meters as follows: The meters capture discrete 15-minute intervals of energy use. Say the demand for the period from 1:00 pm to 1:15 pm on July 15th is 200kW on average for that period, the meter would record that energy use level. The meter runs continuously, and continuously samples the energy use during all of the 15-minute intervals. That provides an average of the demand for each interval. If it happens to be the highest peak in the month, that reading will be recorded as the demand peak.
The example in the Santa Barbara parking structure shows why this is a problem. This is a reasonably new and modern city owned building. The lights stay one 24/7 for most of the structure. A few may go out when the attendants leave or the sun rises. The entry and exit gates operate with some consistency having some busy times and some slow times. The elevators probably work reasonably consistently during the day with a morning work rush and possibly another one early evening. The point being that the demand for electricity does not change much during the course of the day. That means that the whole electric demand will not vary significantly over the course of the month and the demand charges will not be significant.
The responsible garage operator has very little choice but to put the increased demand charge on the usage of the EV charger and now you have a $5.00 plus charge an hour for charging. So what can be done to help deal with this?
When you add two charging stations to the mix you have the possibility of two EVs charging at 30 amp rates with 220 Volts. That is a demand rate of over 12 kW that will last for three to six hours at the most. Now you have a typical 25 KW demand looking like a 37 kW demand and the cost for the whole parking structure goes through the roof (if it has one).
This challenge goes up by a very large multiple when it comes to the use of DC to DC fast chargers. The DC to DC fast chargers come in 25 kW and 50 kW varieties. Most of them pass the current from the grid straight through to the vehicle once converted to DC. Now you have one charger with a 30 minute peak demand of 50 kW. If it is used once a month that peak could determine the billing for an entire facility.
This points to the need for pretty sophisticated charging stations and for a level of charger management that is way beyond the idea of slapping in a few chargers and seeing what happens. The public charging system needs to make business and financial sense. If it does not then the long term success of our electric vehicles may suffer.
These charging rates are for people using the J1772 plugs from chargers like the Clipper Creek, the Blink or the Chargepoint chargers. These are the ones limited to 30 amp charging rates, which means the peak demand would be determined by the Tesla charge rate of 6.2 kWs.
Clearly part of the problem is in setting the pricing by the hour instead of being priced based on the charge rate. Charge point chargers have a 110 plug which NEVs can use. Are they to be charged at the same price as a Tesla for one hour of charging? Are charging rates per hour to be based on the one hour per month when two Tesla’s charge at one garage and spike the Demand Charge?
This gets more complicated as different electric vehicles charge at different rates. Neighborhood electric vehicles (NEVs) charge rates are around half a kilowatt. The Chevy Volts charge rates are around 2.6 kW compared to a 2011 LEAF at 3.3kW. Tesla’s will adjust to the supply and can charge from 24 to 70 amp rates. Most standard J1772 charging stations will only allow 30 amp rates. These mean that Tesla’s charge at rates up to 6.2 kW. The 2013 LEAFs and the Ford Focus can both charge at close to this rate (6.1 kW).
Please submit any ideas about how best to handle these concerns so we can quote you in that article.