Duty cycles and charging strategy: modelling what your fleet really needs
Every good depot decision starts with how your vehicles are actually used. Here's how to capture duty cycles, turn them into a demand profile, and size charging without guessing.
Last updated 15 August 2026
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Almost every expensive mistake in depot electrification traces back to the same thing: sizing the project on assumptions instead of on how the fleet actually runs. Duty cycles are the fix. Get this discipline right and the grid, charger and cost decisions all get easier and cheaper. This guide is about the method — how to model your real demand before you design anything.
What a duty cycle is
A duty cycle is simply the pattern of how a vehicle is used: how far it travels, when it returns to the depot, and how long it sits before its next job. Two vans covering the same mileage can pose completely different charging problems — one back by five and out at eight can charge slowly and cheaply overnight; one on a tight double shift needs fast top-ups. The duty cycle, not the odometer, drives the design.
From duty cycle to energy need
Once you know a vehicle’s daily distance and its efficiency (miles per kWh), you know roughly how much energy it needs each day. Pair that with its charging window — the hours it’s parked and available — and you know how much power it takes to refill in time. Energy needed, divided by hours available, gives the charger size. Do this per vehicle and the depot’s requirement emerges from the bottom up, rather than from a rule of thumb.
Why dwell time beats vehicle count
The instinct to buy one charger per vehicle is usually wrong and always expensive. What matters is dwell time: vehicles parked for ten hours overnight only need modest chargers, and several can share fewer units by charging in sequence under smart charging. Modelling dwell time is what lets you safely install fewer, cheaper chargers and a smaller grid connection.
Building a depot demand profile
Add every vehicle’s charging need across the night and you get a demand profile — how much power the site draws, hour by hour. This is the number your DNO cares about, and it’s where you design for the peak rather than the average, because it’s the simultaneous peak that must fit inside your connection. Telematics data makes this precise; even a good timetable-based estimate beats guessing.
Designing for the real peak
The goal is a strategy that flattens the peak into the hours available: stagger start times, prioritise vehicles leaving early, and spread the rest across the cheap overnight window. A single-shift depot with long dwell times has lots of slack to play with; a double-shift operation has less and may need some faster charging. Either way, the strategy falls straight out of the duty-cycle work — you’re not guessing, you’re scheduling.
The bottom line
Duty cycles are the unglamorous foundation that makes everything downstream cheaper. Capture how each vehicle really runs, turn it into an energy need and a demand profile, design for the peak, and let dwell time shrink your charger count. Start with the Grid Capacity Estimator to turn your charger plan into a demand figure you can take to your DNO.
Go deeper — articles in this guide
- How to work out how much energy your fleet really needs Daily distance times efficiency gives energy per vehicle; add the fleet up and you have your depot's nightly energy need. Here's the method.
- Dwell time: the number that decides your charger spend How long a vehicle sits parked matters more than its battery size. Long dwell means slower, cheaper chargers — and fewer of them.
- Building a depot demand profile from your telematics Your telematics already hold arrival and departure times. Turn them into an hour-by-hour demand profile — the number your DNO actually needs.
- Single-shift vs double-shift depots: two different charging problems A depot where vehicles rest all night is a very different charging challenge from one running double shifts with little downtime.
- Why you usually need fewer chargers than vehicles One charger per vehicle is intuitive and usually wrong. When vehicles rest for hours, several can share a charger by taking turns.