The steps below will help you understand the process for a depot site assessment to understand how much charging infrastructure is needed and estimate hardware and installation costs.

• Review electricity supply. If a site has an energy or facilities manager, they should know the size (in kVA or even MVA) of all supplies. For sites without dedicated managers, inspect the incoming supply to understand its rating and whether it is a single or three-phase connection.

• Identify the location(s) of the supply and distribution equipment to prioritise locations for charging infrastructure. Installing chargers near the power source will help reduce costs.

• Understand the current loads from electrical equipment on site, including any BEVs. The more detailed the data the better; ideally one year’s worth of half-hourly metering data for each supply.

• Understand the charging capabilities and daily energy requirements of each BEV under typical operating conditions. To work this out you will need the following information: useable battery capacity (kWh), maximum charging power (kW) of the vehicle, shift start and end times, and daily energy consumption. You can use the Fleet Planning Tool on this website to help you answer these questions.

• Evaluate whether the current network connection(s) can deliver the energy required in the available charging time.

• If the site has sufficient capacity to recharge the vehicles in the available time, then the next decision to make is how the charging is to be done. Either:

  • There is no limit in terms of power or energy. Vehicles can be charged at maximum power without management without risking overloading the supply. Or;

  • The energy required for charging can be delivered, but it must be managed to avoid overloading the supply due to demands from other equipment. See the mitigating electricity capacity constraints section below.

• Consider future proofing when planning charging needs. If you plan to transition all vehicles to BEV in the next few years, ensure the site has sufficient power available to support this demand.

When many vehicles are charged at the same location, power requirements can exceed the local grid supply capabilities. Smart or load-managed charging can be used at depots to keep power transfer within the site constraints or reduce the cost of upgrading the supply.

• Smart charging is the ability for charging power to be modulated between zero and the maximum power in response to an external control signal.

• Load management is a technique whereby charging power is controlled at a local level to avoid exceeding the maximum capacity of a local electricity network connection

Smart charging and load management may not always be enough to deliver the required charging energy during the available charging time. This can be due to the site having a small, low capacity network connection; wanting to deploy a significant number of BEVs; or a combination of both.

In these cases, either the distribution network operator (DNO) connection must be upgraded, or energy storage and/or on-site generation will be needed. The preferred solution will depend on whether the total cost of ownership of on-site generation and storage technology is lower than the (often significant) cost of upgrading the DNO connection. Engage with your DNO early in the process and seek quotes for connections and upgrades.