Going downhill, regenerative braking can recover some of it. Modern EVs capture 60 to 80% of the gravitational potential energy on a long, controlled descent under ideal conditions. The practical recovery is often lower, at high speeds the brakes are used more aggressively, and on short descents regeneration barely registers before the next climb begins.

The critical constraint is battery headroom. Regenerative braking can only return energy to a battery that has room to receive it. A vehicle that departed at 100% state of charge cannot accept regenerated energy until the battery has depleted enough. If the route has a long descent early and a long climb later, the vehicle may capture very little of the downhill energy and spend the full cost of the uphill. The routing calculation needs to know this about the specific route, not assume that downhill balances uphill.

On net, elevation-related range loss is asymmetric. Uphill costs more than downhill recovers, and the degree depends on the route profile, the vehicle's regenerative capability, and the departure state of charge. A routing engine using a flat-road consumption assumption produces estimates that are consistently optimistic on mixed-terrain routes.

For a fleet operating in flat urban terrain this is invisible — the tool works fine. For a fleet delivering to industrial estates on ridgelines, running inter-city routes through hilly countryside, or operating anywhere with meaningful topography, it is a systematic planning error with a consistent failure pattern: vehicles that almost make it before needing an unplanned stop.