Fleet depot and workshop EV charging on a limited supply

A depot or workshop rarely runs out of parking bays first. It runs out of amps. EVs were 25.8 % of new car sales in the first half of 2026, but electric trucks and vans were still below 1 % of their markets [2], so many fleets are planning their first chargers now. This guide covers sizing, the supply constraint, workshops and daily operations.

How do you size EV charging for a fleet depot?#

Size fleet depot EV charging from energy, not charger count. Multiply each vehicle's daily distance by its consumption in kWh per km, and add charging losses, to get the energy it needs each night. Divide the fleet's total by the hours the vehicles are parked to get the average power the supply must deliver.

1. Energy per vehicle = kilometres per day × kWh per km × (1 + losses). Take consumption from telematics or the Green Vehicle Guide, and expect loaded vans to use more than the label.
2. Dwell window: from the last vehicle in to the first vehicle out, minus a buffer.
3. Average power = total fleet energy ÷ window hours.
4. Current per phase at 400 V three-phase = kW × 1,000 ÷ (√3 × 400), about 1.44 A per kW.
5. Compare with measured spare capacity in that window: supply rating minus measured non-EV load, minus a margin.

Plan for the worst normal day, not the average. Typical daily needs look like this:

Every figure in that table is an illustrative assumption; use your own vehicles' data. The capacity calculator runs the same arithmetic for your site.

Can a 100 A three-phase supply charge 10 vans overnight?#

It can, if the chargers are managed and the measured spare capacity allows it. In the illustrative example below, 10 vans need 330 kWh over a 10-hour night: an average of 33 kW, or about 48 A per phase at 400 V. A 100 A supply with 25 A of overnight load and a 10 A margin leaves 65 A per phase spare, which covers it.

The illustrative arithmetic, step by step:

• Energy. Each van drives 100 km at 0.30 kWh/km: 30 kWh at the battery. Allowing 10 % for charging losses, that is 33 kWh from the supply per van, or 330 kWh for the fleet.
• Window. Vans are parked from 9 pm to 7 am: 10 hours.
• Average power. 330 kWh ÷ 10 h = 33 kW, and 33,000 W ÷ (√3 × 400 V) ≈ 47.6 A per phase.
• Spare capacity. The supply is 100 A per phase. Measured overnight non-EV load (lighting, refrigeration, IT, security) peaks at 25 A per phase. Keeping a 10 A margin leaves 65 A per phase, about 45 kW.
• Fit. 45 kW × 10 h = 450 kWh available against 330 kWh needed: about 36 % headroom. On these assumptions the supply tops out at about 13 vans (450 ÷ 33).
• Unmanaged. Ten 11 kW three-phase chargers (16 A each) starting together would draw 160 A per phase, about 2.5 times the spare 65 A. A static design fits only four of them (64 A).
• Managed. All 10 chargers share the 65 A: 6.5 A per phase each when every van charges at once, about 4.5 kW. A 33 kWh van then takes about 7.4 hours, inside the window, and the remaining vans speed up as others finish.

Indicative only; maximum demand must be determined by your electrical designer under AS/NZS 3000.

Depot overnight, per phaseIllustrative

Non-EV loadSpare for EVsManaged EV loadUnmanaged EV load10 A margin

Two cautions. Measure, don't assume: the same depot at 2 pm, with a workshop running, may have far less to spare. And every AC charger has a minimum current it can be set to, so push the fleet much past this example and bays must pause and take turns.

How many chargers per vehicle, and AC or DC?#

For vehicles parked overnight, one AC charger per vehicle is the simplest arrangement. Nobody moves vans at 2 am, and with load management the extra chargers cost hardware, not supply capacity. Fewer chargers than vehicles works when some vehicles need little energy. DC suits short dwell times and multiple shifts, at much higher cost and supply demand per bay.

One Australian installer's rule of thumb is "one charger per two to three vehicles for overnight charging, or one per vehicle if daily turnover is high" [6]. Sharing a charger means someone swaps plugs mid-shift; sharing the supply across one charger per vehicle does not.

On AC, the car's on-board charger caps the rate whatever the wall unit can deliver, and a DC charger bypasses it entirely [7]:

Why is the supply connection usually the constraint?#

Chargers are quick to add; supply capacity is not. A depot's connection was sized for its existing load, and every charger allowed to run at full rate adds its whole rating to the design. Upgrading the connection can be slow and costly, so the cheaper path is usually to measure what the site draws and fit charging into the gap.

AS/NZS 3000 clause 2.2.2 allows maximum demand to be determined by calculation, assessment, measurement or limitation, and the Electric Vehicle Council's guidance treats a load-management system as creating a definite duty cycle under the assessment method, with protective devices as the backstop [3]. That is the designer's call and responsibility, but it is why load management is a design tool and not only an operational one.

Demand tariffs then shape when charging should happen. Ausgrid's capacity charge uses the highest half-hour kVA between 3 pm and 9 pm on working weekdays over the previous 12 months [4]. Powercor uses the highest 15-minute kVA between 7 am and 7 pm on workdays over the prior 12 months [5]. Vans that return at 4 pm and all start at full rate inside such a window can set the charge for a year. Either delay charging until the window closes, or cap the site's total so EV load cannot add to the peak. Our maximum demand guide works through the numbers.

How should workshops and dealerships charge EVs alongside compressors, hoists and welders?#

Measure the workshop's non-EV load and give EVs only what is left. Compressors, hoists and welders switch on and off all day, so a fixed EV allowance must assume they all run at once and leaves cars very little. Dynamic sharing uses the gaps between those loads, while a margin and the circuit breakers cover motor starts.

An illustration: a workshop has 80 A per phase, and its tools peak at 60 A but usually draw about 25 A. With a 5 A margin, a static design gives EVs 15 A per phase all day. Sharing against measured load gives them about 50 A per phase most of the time, and pulls back towards 15 A when everything runs.

Motor starts need respect. A standard motor started direct-on-line draws about 5 to 7 times its nominal current while it runs up [8]. A control loop that updates every few seconds handles sustained loads, not that inrush, which is why the margin stays and protection coordination stays with the electrical designer. Load management sits on top of protection, never instead of it.

Workshops also see every brand of car. Choose chargers that implement OCPP smart charging so you can mix charger brands and change management system later; see what "OCPP compatible" means. Per-bay energy records let you pass charging costs to customers through your own invoicing, and stock vehicles can be capped low so they stay charged without crowding out customer work.

How should depot charging run day to day?#

Day-to-day depot charging needs five things: drivers identified at the charger, energy records per driver or vehicle, a yard display showing what is charged, alarms routed to whoever fixes them, and a way to favour urgent vehicles. It must also keep working when the internet connection does not.

Driver identification and FBT records#

RFID cards per driver tie every session to a person. The resulting kWh records support internal cost allocation and the paperwork around fringe benefits tax.

The ATO says private use of an eligible electric car, and the cost of electricity to charge it, is exempt from FBT, but the benefit is still reportable, so employers work out a notional taxable value [1]. The exemption covers cars, defined as designed to carry less than one tonne and fewer than nine passengers, so check each van. The ATO asks employers to keep records showing how they worked out electricity costs, and its home charging rate cannot include commercial charging costs unless the share of charge by location can be accurately determined. Per-driver depot records are raw material for that; your tax adviser decides how to use them.

Yard display and alarms#

A wall screen showing which bays are charging, finished or faulted tells the first driver in which van to take. Faults should reach the person who fixes them, such as the service desk or on-call electrician, not a portal nobody watches.

Priority vehicles#

The on-call ute matters more than the pool car. Lower or pause the caps on less urgent bays so the shared supply flows to the vehicle that has to leave first.

When the internet drops#

Ask where load management runs. If it lives in the cloud, find out what each charger does when the link fails: a running session typically keeps its last limit and new sessions use a default profile, and neither reacts to the building's load until the link returns. A default too high trips the supply; one too low leaves vans flat at dawn. A controller on site keeps managing whatever the internet does.

Where Nohmad Edge CSMS fits#

Nohmad Edge CSMS is an on-site EV charging management system built for this problem: an OCPP 1.6J CSMS and a load-management engine running together on one industrial PC in the switchroom. It measures the depot's real load and shares what is left across AC chargers, per phase, every 10 seconds, with or without an internet connection.

• Load management. Cascading limits from the incoming supply through each switchboard to each charger. Each budget is the node's limit minus the measured non-EV load, such as compressors and hoists. Limits apply per phase where meters and charger phase mappings exist, otherwise on the worst phase. Sharing is equal current or equal power, and below a 6 A floor a bay pauses or holds at the floor. An idle-bay policy decides what finished vans still plugged in get.
• Chargers. Any AC charger that implements OCPP 1.6J smart-charging profiles. Tested so far on simulators (120 chargers) and on real chargers including an Orbis VIARIS UNI; there is no published compatibility list yet. Unknown chargers wait in Pending until an operator approves them. DC charger support is on the roadmap.
• Drivers and records. Per-charger RFID allow-lists of up to 10,000 tags, managed through the API today. Session records hold kWh, RFID tag, charger and bay, exportable to CSV and filterable by tag, bay and date. They are operational records, not pattern-approved metering.
• Yard and alarms. The Status grid is a chrome-less wall display for depots. 42 live alarm types, with JSON alarm webhooks to a service desk.
• Priorities. Per-charger pause and resume, operator current caps, force-stop, site hold and a site-wide emergency drop.
• Demand. Optional instantaneous and rolling-average kW caps on the incomer. They work in kW, not kVA, need a meter reporting voltage at the incomer, and are not aligned to your network's metering intervals. Edge CSMS does not schedule charging by time of day or departure time.
• Offline. If the internet drops, nothing changes, and data stays on the box. If a meter goes stale, active chargers are set to their configured safe current and a critical alarm is raised. A charger that loses contact with the box keeps its last allocation for the session in progress; sessions that start while it is cut off use an offline fallback profile (10 A by default). Breakers remain the last line.
• Metering. A built-in preset for the Algodue UPM209 over Modbus TCP (validated against an emulated meter so far); its RGW kit uses Rogowski coils, which suit existing switchboards [9]. Other Modbus TCP meters connect through a register map.

Read more about Edge CSMS and fleet and workshop charging, or run your numbers through the capacity calculator. Electrical contractors can work with us. Connecting to a building management system? See EV charging and BMS integration.

Sources#

1. Australian Taxation Office, Electric cars exemption, last updated 1 April 2026.
2. Commonwealth Bank newsroom, EVs now 1 in 4 new car sales, reporting the Electric Vehicle Council's State of EVs 2026, 30 September 2026.
3. Electric Vehicle Council, Determining maximum demand for an apartment complex with EV chargers, 2024.
4. Ausgrid, 2026–27 Pricing Proposal, Statement of compliance, 31 March 2026, published by the AER.
5. Powercor, 2026/27 Pricing, 7 May 2026, published by the AER (section 2.5, kVA demand).
6. EVSE Australia, Commercial EV charging in Australia 2026 guide.
7. Gridly, On-board charger, April 2026.
8. MB Drive Services, Direct on-line start.
9. Algodue, UPM209RGW product page.