Smart charging vs an on-site battery: when to use which
Both help you fit charging within your grid limit — but they solve different problems. Here's how to tell which one your depot needs.
Last updated 15 August 2026
Smart charging and an on-site battery are often talked about together, because both help you charge more within a limited grid connection. But they work differently, and knowing which solves your problem saves money.
Smart charging spreads load over time
Smart charging works by rescheduling — spreading the fleet’s charging across the hours available so the peak never exceeds your connection. It costs relatively little (it’s software) and handles most depots, because vehicles usually sit for long enough to take turns. If your problem is “lots of vehicles, plenty of overnight time,” smart charging alone is usually the answer.
A battery adds power you don’t have
A battery supplies extra power at the moment you need it. It charges gently over many hours, then discharges in a burst to cover a peak that’s higher than your connection can deliver — even after smart charging has spread the load as much as it can. If your problem is “a genuine simultaneous peak that exceeds the connection, and reinforcing it is slow or costly,” a battery earns its place.
Use them together
In practice the two are complementary. Smart charging is the foundation every depot should have; a battery is added on top when scheduling alone can’t flatten the peak enough, or when you also want to store cheap energy or add resilience. The sequence is almost always: exhaust what smart charging can do first, then size a battery only for the gap that remains.
The costly mistake is buying a battery to solve a problem that clever scheduling would have solved for free. Model the smart-charging case first with the Grid Capacity Estimator, and only reach for storage when the numbers genuinely need it.