Transformer Sizing for EV Chargers

How EV charger load adds to your transformer

Each AC or DC charger draws rated power while vehicles charge. Multiple guns may operate simultaneously at peak.

• Sum connected kW, then apply diversity based on usage pattern
• Add existing building load (HVAC, lifts, lighting)
• Include power factor and harmonics considerations for DC stacks
• Reserve headroom (typically 20–30%) for future bays

Illustrative sizing scenarios

Four 22 kW AC chargers in a society may need a dedicated panel and possible transformer upgrade if the existing load is high.

A 120 kW or 240 kW DC hub usually requires dedicated HT/LT infrastructure planned with DISCOM and a licensed electrical consultant.

Thunder EV's AI Project Planner captures bay count and charger mix to flag upgrade scope early.