The electrical connection is the largest fixed cost in a charging site and the one most often over-specified. Sizing it correctly is worth more than any pricing decision, because demand charges recur every month whether or not the capacity is used.
Sanctioned load is not the sum of your chargers
The instinct is to sanction for simultaneous maximum: four 60kW chargers means 240kW plus overheads. That is correct only if all four will genuinely deliver full power at the same moment, which — outside a depot with a fixed return schedule — is rare.
The alternative is to sanction for realistic simultaneous demand and enforce that ceiling with charging profiles. This is the single largest capex and opex reduction available at most sites, and it is a software decision, not an electrical one.
Diversity, honestly assessed
| Site type | Realistic simultaneity | Note |
|---|---|---|
| Public DC, 2–4 bays | 60–80% | Peaks are real and clustered; do not cut this too fine |
| Public DC, 8+ bays | 50–65% | Larger sites diversify naturally |
| AC destination | 40–60% | Long dwell, staggered arrivals |
| Workplace AC | 30–50% | Arrival spike in the morning, then idle |
| Depot | 100% without management | Fleets return together — this is why depots need load sharing |
The depot row is the important one. A fleet returning at the end of a shift is the worst case for diversity: every vehicle plugs in within minutes. Depots without load management must be sanctioned for the full simultaneous load, and depots with it can often be sanctioned for less than half.
What load management buys you, in rupees
Take a depot with 28 charge points at 22kW: 616kW of connected load. With overnight charging across a six-hour window and vehicles needing an average of 90kWh each, the actual energy requirement is 2,520kWh — deliverable within the window at around 420kW if perfectly spread, and comfortably at 350kW with a staggered schedule.
The difference between sanctioning 650kVA and 400kVA, at ₹250/kVA/month, is ₹62,500 every month — ₹7.5 lakh a year, indefinitely — plus a substantially smaller connection cost up front. That is the commercial case for smart charging, and it does not depend on any energy-price arbitrage.
Protection and safety
- RCD type per the charger specification — Type B, or Type A where the unit provides its own 6mA DC leakage detection.
- One RCD per charge point rather than a shared one, so a fault on one unit does not take the site down.
- Surge protection at the distribution board. Chargers are expensive and lightning is not theoretical.
- Earth resistance measured and recorded at commissioning, not assumed from the site drawing.
- Emergency stop where required, with its state visible to the platform so an activated stop is not mistaken for a fault.
Cable sizing and voltage drop
Charging loads are continuous and long-duration, which makes voltage drop across long runs a practical problem rather than a theoretical one. Size against the actual run length including vertical rises, not the plan distance, and check the drop at full load rather than at nominal.
Where the run is long, it is frequently cheaper to move the distribution point closer to the chargers than to upsize the cable — and it leaves you room for the units you will add later.
Plan the second phase now
Sites that succeed get more chargers. Leaving spare ways in the distribution board, conduit capacity in the trench and physical space at the panel costs very little during the original civil work and a great deal afterwards. Trenching a car park twice is the most avoidable expense in the industry.