Electric vehicle (EV) charging equipment vendors often use different terms for their products. Wading through those options and varying vernacular when constructing or renovating a commercial property, especially in states that require a certain number of chargers for new projects, can be confusing.
Though VCA Green offers a robust electric vehicle and/or renewable energy consulting service, below we explain a few common charging infrastructure characteristics so you can see through the initial sales pitch on your own.
First, keep these two questions in mind when it comes to EV charging installations at your property:
1) How does EV charging affect the grid and the rates I pay for the electricity to charge EVs?
2) How much strain does EV charging put on my property’s electrical system and how can I keep it safe?
Knowing that you want to allow EV owners to charge their vehicles conveniently and quickly (more on that here), certain technologies can address the two points above and deliver high customer satisfaction. At the end we’ll touch on cost recovery and the value of EV charging.
In this publication, regardless of how manufacturers might typically refer to different aspects of EV charging, we’ll use “load management” to describe the entire system’s load on the grid and “charge balancing” as the method to prevent overloading your property’s electrical panel or any one circuit therein.
Load management
With load management, the controller in the “charger” (formally known as electric vehicle supply equipment or “EVSE”), prevents impacting peak demand at your property by instructing EVSE to deliver the just the right amount of energy to still provide charging, but without setting new high demand fees. EV load management is delivered via a software-based, typically SaaS, solution, where the load management software constantly communicates with the electricity infrastructure, charge points, and charging EVs. EV charging load management can be static, where charging is restricted or limited based on the time of day, or it can be dynamic, where it adjusts energy consumption in real-time.
Dynamic load management
To illustrate dynamic load management below, we assume that the owner arrives home at 6 p.m., plugs in their EV, and starts to use other electrical appliances in their house or apartment. This causes the peak consumption at those hours. (EV owners should program their cars not to charge during peak times, but not all owners do this as a matter of habit.)
Adding EV charging consumption atop normal peaks can cause new high peaks, drive up costs, or even overload the electrical system:
To avoid exceeding the power capacity, dynamic load management (below) will charge with the maximum possible current up to the limit programmed in the system. The electrical limits of your infrastructure or the financial limits of your billing tariff determine this to prevent you from accidentally moving up to a higher tariff. You can comfortably turn on the water heaters, electric stoves, irons, other electrical appliances, and still keep an EV plugged in comfortably.
The system measures the power consumption of the house or apartment building and allocates remaining available power to your EV charging network.
What is a charge balancing system?
A charge balancing system lets the charging site operator control how much power each station can use when multiple EVSE units are connected to the same electrical circuit. The EVSE communicates with other EV charging stations on the same electrical circuit without ever exceeding the maximum capacity of that circuit, automatically balancing electricity usage.
With equally distributed charge balancing, which we will refer to as “dumb balancing” (not that it’s not smart to balance charging), each EV charger gets the same amount of electricity depending on maximum circuit amps and how many stations are in use. If the electrical circuit can provide 80 amps and four 40-amp EVSEs are in use (connected to an EV), each EVSE will be allowed to receive an equal amount of 20 amps. If one electric car leaves and there are three active EVSE as in the diagram below, each one will be allowed to get up to 26.6 amps.
A dumb balancing system doesn’t know how much energy is being used, it just knows that it can’t exceed the electrical limit due to the number of EVSEs in use. The benefit is that all available power will be equally accessible although that might not be the most beneficial thing to do.
Dynamic charge balancing
The dynamic charge balancing systems work differently. There are as many methods as there are manufacturers, but the bottom line is that these “smart balancing” systems know how much energy each EVSE demands and allow the maximum amps to be distributed as needed. Using our four 40-amp charging station example above, let’s say that one of the cars is a plug-in hybrid and only draws three amps. Another economy battery EV (BEV) is nearly fully charged and is only drawing 11 amps. That leaves 66 available amps for the other two EVSE.
Let’s say that the last two sport BEVs can only charge at 32A each. This smart balancing system has now enabled much faster charging than would exist with a dumb system. All four EVs are plugged in and charging at their maximum rate; whereas, if it were a dumb system with 4 cars plugged in, they would have been allowed 20A each. The other two EVSEs would automatically be allowed up to 40A each when the hybrid and economy BEV get fully charged.
Image Source: Blinkcharging.com
How do EVSE communicate balancing?
Physically, EVSEs communicate with each other via either wi-fi, Bluetooth, ethernet, Modbus, or other network. Software wise, they may have a proprietary protocol or an open protocol like Open Charge Point Protocol (OCPP) network services. While some EVSEs provide balancing through OCPP and/or some proprietary network subscription, other EVSEs can communicate with each other directly through the communication network, possibly eliminating the need for a paid subscription for each EVSE.
Why would you want EVSE charge balancing?
While EVSE charge balancing likely doesn’t come free, there are many advantages:
1) Charge balancing allows you to connect multiple EVSE to a single circuit, reducing electrical infrastructure cost.
2) In existing buildings, it helps you install more chargers on your existing electrical infrastructure, improving services to the tenants or residents.
3) Enables faster charging cars to charge faster up to the maximum rating of the EVSE when power is available rather than restricting all cars to a slower speed, thus increasing customer satisfaction.
4) Because most EVs can’t charge continuously at their nominal rate and must reduce the power they draw, it enables the electrical system to distribute remaining power to more EVs.
5) You can better control the cost of electricity used for charging during peak and off-peak hours, weekdays vs. weekends, holidays, etc.
6) Mitigates the likelihood of electrical system overloads and can reduce heat buildup which shortens life expectancy.
7) Good software-based systems even allow analytics and diagnostics to help with fleet or EVSE management.
How much power (kW) does an electric vehicle need?
To understand this, let’s think about the old gasoline powered cars. In five minutes at the pump, you could put enough gas in your car to travel 400 miles. That’s 4,800 miles an hour of refueling. Since the average vehicle annual mileage is somewhere around 12,000 to 15,000 miles, you could say that a gas car only needs three hours at the pump per year. It’s the same analogy with electric vehicles, but with charging speeds varying widely from three miles per hour to 1,000 miles per hour as fast chargers, we need to know a little more.
The average electric vehicle travels between three and four miles per every kWh. At 12,000 miles a year that’s 3,500 kWh per year (at ~3.5 miles/kWh). At a charging rate of seven kW (typical for many BEVs) and 3.5 kW (typical for most hybrids), that’s 500 to 1,000 hours per year, 40 to 80 hours a month, or 10 to 20 hours a week of charging time needed, respectively.
A 32-amp EVSE is about seven kW, so most BEVs will need to use it twice a week overnight. Plug-in hybrids would not need more than a 16-amp EVSE because very few of them can even charge at rates higher than 3.5 kW. Very few EVs can charge faster than 11 kW – those are typically $100,000+ cars. Additionally, no current EV sustains that kW all the way up to 100% charged. That means that anything over a 50A charger is unlikely to be used anywhere near capacity for any significant amount of time.
How much energy (kWh) will electric vehicles consume?
As listed above, a 12,000-mile yearly usage will result in about 3,500 kWh a year. At $0.12/kWh that’s only $420 a year in electrical cost. For a commercial project that needs to recover the cost of EVSEs, installation, maintenance, utility, and management costs, charging $0.50/kWh is not unheard of which is $1,750 a year. Gasoline at $4.00/gallon would be $1,920 at 25 MPG.
Therefore, the EV owner still saves money while the charger is a profit center for commercial projects or multifamily buildings. Considering multifamily for a moment, it’s not unreasonable to budget 3,500 kWh per EV owner per year. However, you may want to adjust for local demographics and commuting distances.
Summary
We reviewed a lot of numbers, but the point is that having plenty of low- to medium-power EV charging equipment might be more convenient for EV owners. Adding more chargers is also convenient for tenants and occupants that have assigned spaces or who don’t like to return to their cars to move them to a non-charging spot when the car is fully charged, as the “charging community etiquette” dictates.
More chargers mean more EVSE available and increases the likelihood they’ll be used. Making sure they incorporate load/grid management can keep your overall electric bill in check. Making sure they incorporate a charge balancing method of some kind can reduce your electrical infrastructure costs.
Finally, before purchasing, make sure your selected EVSE has billing/management software that integrates with your accounting system. Incorporating software is very important, which is why we leave you with this as the final thought.
Contributing writer: Wayne Alldredge
Moe Fakih, Principal
mfakih@vca-green.com
Robyn Vettraino, Principal
rvettraino@vca-green.com