Utility Engagement and Electrical Infrastructure
Electrical Infrastructure Needs
The electric infrastructure required for charging is usually focused on the needs of the larger “non-cutaway” buses, which tend to weigh 33,000 lbs. or more. These buses typically have a battery capacity of around 150 kWh and a range of roughly 120 miles.
To determine charging infrastructure needs, school districts need to identify how many buses need to be charged per day, and in what time windows. For example, in some districts a typical daily route could be as much as 50 miles in both the morning and afternoon shifts, for a total of 100 miles per day. This consumes slightly over 80% of the bus’s battery capacity each day (roughly 125kWh). School buses typically have two charging windows: late morning/early afternoon (five hours between 9am-2pm), and evening/night (12 hours between 5pm and 5am), for a total of 17 hours, requiring a minimum 7.35 kW charging rate per hour to fully charge. In this case, a DC Charger would likely be a better choice, given that a 60kW model could charge a single bus in a little over 2 hours, and support charging as many as five buses sequentially given the above routing parameters
Costs & Utility Engagement
Charging infrastructure costs range very widely depending on both the level of charging technology needed (Level 2 vs. DCFC), the number of chargers needed to service the fleet, and the amount of new electrical service capacity needed from the local utility.
Unfortunately, there is no easy rule of thumb for determining the cost of charging infrastructure. Individual Level 2 station installations plus equipment can range from ~$15,000 to $35,000 or more installed, while individual DC Fast Charging Stations can range from $30,000 installed to $80,000 or more depending on such variations as the distance of the chargers from the service panel, any utility relocations needed, and the cost of trenching, conduit, and other materials and labor. Likewise, the cost of electrical service upgrades varies widely, as does local policies for who pays the upgrade cost – the utility or the school district.
Coordination with electric utilities is critical to site planning and infrastructure deployment. Depending on the fleet parameters, a school may need to establish a new electricity service (new meter and infrastructure on site), upgrade the school’s electricity systems, and, potentially, pay for upgrades to the utility’s electricity distribution system. Some utilities offer special rate designs for electric vehicle charging, typically using a discounted time-of-use model to encourage charging in the off-peak hours.