How Many EV Charging Stalls Does Your Workplace Need?

One of the first questions every facilities manager asks when planning a workplace EV charging rollout is: how many stalls do we actually need? Install too few and you've solved nothing - you'll have the same waitlists and frustration as before. Install too many and you've sunk capital into idle infrastructure. The right answer depends on five variables, and this guide walks through each one.

The Formula

The simplest version: target a stall-to-EV ratio of 1:3 to 1:4 for Level 2 charging. This assumes typical session durations (30–60 minutes of actual charging time per visit), typical occupancy hours (8am–6pm), and a roughly even distribution of arrivals through the day. A workplace with 60 EVs needs 15–20 stalls at this ratio.

But that formula breaks down in two common scenarios: high-concurrency workplaces (where most employees arrive at roughly the same time, like a 9am start with minimal flex hours) and long-session workplaces (where employees charge for their full 8-hour workday rather than the 1–2 hours their battery actually needs). In those cases, the effective ratio moves toward 1:2.

The Five Variables

• Current EV count: Survey your parking lot or poll employees directly. Don't undercount - employees are often reluctant to admit they drive EVs if they don't think it matters.
• EV adoption trajectory: If 10% of your workforce drives EVs today and you're in a market where EV adoption is growing 20% per year, plan for 18–25% within two years.
• Average session duration: This is the hardest to estimate without data. Use 45 minutes as a starting point for a typical Level 2 charger and a typical battery state-of-charge on arrival.
• Arrival distribution: If employees arrive in a tight window (e.g., 85% between 8:30 and 9:30), peak concurrency is much higher than if arrivals are spread across 3–4 hours.
• On-site parking days: For hybrid workplaces, factor in that each employee is only on-site 2–3 days per week. This reduces effective demand but complicates scheduling.

A Worked Example

Consider a 300-person company with 45 current EV drivers. Employees arrive primarily between 8:00 and 10:00am. Average session duration is about 50 minutes based on surveyed battery needs. The company is hybrid: employees are on-site an average of 3 days per week, meaning about 27 EV drivers are on-site on any given day.

With a 2-hour arrival window and 50-minute average session, each stall can serve about 2.4 cars during peak arrival. To serve 27 concurrent drivers in a 2-hour window, you need roughly 11–12 stalls. Add 20% buffer for future growth and out-of-service incidents, and you arrive at 14 stalls as a planning target.

Start With Less, Plan For More

The most common mistake is installing the minimum number of stalls with no electrical capacity for expansion. Conduit and panel capacity are cheap to rough in during initial installation and expensive to add retroactively. Even if you install 8 stalls today, run electrical infrastructure for 20. It's typically 10–15% of the additional stall cost to do it during initial construction versus 60–80% of the cost to retrofit later.

Good coordination software will give you the utilization data to make evidence-based expansion decisions. Once you see stall utilization consistently above 80% during business hours for two consecutive months, it's time to add capacity.