How many EV chargers does a last-mile fleet need?

The quick answer —“one charger per vehicle”— is rarely the right one.

A fleet of 20 electric vans may need 20 connectors, ten shared chargers or fewer active units. It depends on how much energy must be recovered, how long each vehicle actually stays at the depot, how much power the site can provide and how much operating margin the fleet wants to keep.

The useful question is not how many EVs the fleet owns. It is whether every required vehicle will be ready to leave the next morning when the night does not go perfectly.

That shift avoids two expensive mistakes: overbuilding infrastructure that spends most of its life underused, or installing a system so tight that one late return disrupts the whole plan.

Charger, connector and charging session are different things

Three terms are often mixed together in commercial discussions:

• Connector or electrified bay: the physical place where a vehicle can plug in.
• Active charger: the unit able to deliver power at that moment.
• Charging session: the time during which one vehicle occupies and uses that unit.

A depot can prepare 20 bays, install ten chargers and charge 20 vehicles in two waves. It can also install 20 chargers and use only part of them simultaneously because the site’s power limit constrains the total.

A vehicle-to-charger ratio therefore means very little without energy demand and timing.

Start with overnight energy

The first question is how much energy the fleet must recover before the next departure.

Then include charging losses and a sensible operating margin.

A simple example

The batteries consume 336 kWh. Replacing that energy from the grid requires about 373 kWh. With the margin included, the depot should plan for roughly 429 kWh.

We still do not know the number of chargers. For that, we need time.

The real charging window converts energy into power

If every vehicle returned at 18:00 and left at 06:00, the theoretical window would be 12 hours.

That does not mean installing exactly 35.8 kW is enough. It is an aggregate average. Vehicles do not always arrive together, they do not need the same amount of energy and the final hour should not be treated as risk-free capacity.

The relevant measure is the effective window for each vehicle. A route returning at 21:30 and departing at 04:45 has a little over seven hours, even if the depot is active all night.

Energy and power answer different questions

A fleet may need 500 kWh overnight without needing 500 kW of instantaneous power. A long window allows that energy to be recovered at a much lower rate. The reverse is also possible: modest energy demand can require high power when vehicles return late, operate in two shifts or leave very early.

Three common infrastructure strategies

One charger per vehicle

This is the simplest model to operate. Every vehicle has a bay and no rotation is required.

It works particularly well when availability is critical, returns are irregular or nobody can move vehicles overnight.

The trade-off is higher upfront investment and the risk of maintaining many underused units. More chargers also do not remove the site’s power constraint.

Shared chargers

Several vehicles use the same unit at different times.

This can reduce CAPEX, but only when charging windows are long enough, energy per vehicle is moderate and a late arrival does not block the following sessions. The fleet must also decide who moves vehicles or how charging priorities are automated.

Charger sharing is not only an electrical decision. It is an operating rule.

Infrastructure prepared for growth

Many depots benefit from preparing ducts, distribution boards and parking bays for a larger future fleet while installing only the equipment required for phase one.

The important decision is to define what will trigger the next investment: more vehicles, higher overnight energy, less margin, new schedules or a contractual requirement.

Nominal charger power is not usable depot power

Four 22 kW chargers add up to 88 kW nominally. The fleet will not use all 88 kW if lighting, offices, HVAC or cold rooms leave only 45 kW available for vehicles.

There is a third limit: the vehicle itself. A 22 kW AC charger will not deliver 22 kW to a van whose onboard charger accepts 11 kW.

The design therefore has to reconcile three constraints:

1. available site power;
2. aggregate power of active chargers;
3. charging power accepted by each vehicle.

When can vehicles share chargers?

A first estimate can calculate the minimum number of active units from power:

Two fleets with identical daily energy can still need different layouts. A depot where every van returns at 17:00 and leaves at 07:00 is not equivalent to one where half arrive after 22:00 and several depart before 05:00.

Safe charger sharing requires checks on:

• individual return and departure times;
• energy still required on arrival;
• next-day route priority;
• whether vehicles can actually be moved;
• response to a failed session;
• dynamic load management;
• ownership of exceptions.

Operating margin is not wasted capacity

A system running at 98% utilisation on an average night is not robust.

Margin absorbs winter consumption, longer routes, late returns, lower charging efficiency, one charger being unavailable or an earlier-than-planned departure. The right percentage depends on service criticality and the alternatives available.

Example: 18 vans and four chargers

In the BaseFit last-mile case study we assessed 18 vans, 12 route families, four AC chargers and 95 kW of contracted power.

The model found ten routes with at least one reasonable electric fit. Even so, the recommended first phase contained six vehicles.

The constraint was not a lack of compatible vans. It was the combination of overnight energy, charger capacity, site power and resilience under adverse scenarios.

The depot could support a first phase, but not every technically compatible route without more capacity or a change in operations.

Signs that the design is too tight

Revisit the plan when:

• average required power is too close to effective available power;
• every charger must run for almost the entire window;
• one late return forces public fast charging;
• one charger failure compromises several departures;
• rotation depends on moving vehicles during the night;
• there is no priority by departure time or energy need;
• the next fleet phase requires rebuilding the installation;
• the calculation uses average routes rather than demanding days.

Before requesting an installer quotation

The fleet should enter that conversation with these inputs defined:

1. vehicles planned for each phase;
2. daily energy by vehicle or route family;
3. real return and departure times;
4. maximum charging power accepted by the vehicles;
5. net power available at the depot;
6. reserve policy;
7. dedicated or shared charger strategy;
8. a scenario with one unit unavailable;
9. the trigger for the next expansion;
10. responsibility for connections, priorities and incidents.

With that information, the installer can design against a defined operating need. Without it, the proposal is more likely to be driven by parking bays, available products or theoretical power.

So, how many chargers are needed?

The answer cannot be obtained by counting vehicles.

It comes from combining energy, time, power, simultaneity, genuine sharing potential, incident margin and the growth plan.

Charger sizing is also only as good as the route-energy assumption behind it. The guide to EV route suitability explains why average distance is not enough.