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.
Last updated 15 August 2026
Everything downstream — chargers, grid, cost — depends on one figure: how much energy your fleet actually needs. Working it out is more straightforward than it sounds.
Energy per vehicle
For each vehicle, take its typical daily distance and multiply by its energy use (kWh per mile, or divide distance by miles per kWh). A van covering 80 miles a day at around 3 miles per kWh needs roughly 27 kWh to refill — a useful, defensible number you can build on. Do this from real route data where you have it; a good estimate beats a guess.
Add the fleet together
Sum every vehicle’s daily need and you have the depot’s total nightly energy requirement — the amount of electricity you must deliver between vehicles returning and leaving again. This is the foundation for sizing chargers and for the demand profile your DNO will care about.
Allow for the real world
Brochure efficiency is optimistic. Real energy use rises with cold weather, heavy loads, heating and hills, so add a sensible margin rather than planning to the ideal figure. It’s better to design with headroom than to discover a shortfall on a frosty morning. The same caution applies to range: plan around comfortable daily coverage, not the theoretical maximum.
With energy-per-vehicle and a fleet total in hand, you can size charging properly — pairing each vehicle’s need with its dwell time to choose charger power, and feeding the fleet total into your grid conversation. Start the numbers with the Grid Capacity Estimator.