Electric Bus Depot Charging: 45 Chargers, 73 Buses

When you plan [electric bus depot charging infrastructure](/solutions), the first question is deceptively simple: how many chargers do you actually need? A recent project in Poland offers a clean, real-world answer. The Upper Silesian-Zagłębie Metropolis (known as GZM) has just completed a fleet-renewal rollout, and the numbers are worth studying for any Indian city — or any Himachal Pradesh operator — sizing up its first e-bus depot.

Here is the headline figure: GZM took delivery of 73 battery-electric buses and only 45 chargers. That is roughly one charger for every 1.6 buses — not one charger per bus. Understanding why that ratio works is the key to building charging infrastructure that is affordable, reliable and future-ready.

What Poland's GZM Project Actually Delivered

According to industry publication electrive, the Upper Silesian-Zagłębie Metropolis completed the delivery of 73 battery-electric buses and 45 chargers, supplied by Solaris and Irizar, as part of a fleet-renewal programme worth almost PLN 305 million (around €70.5 million). The vast majority of the cost was financed through Poland's National Recovery and Resilience Plan (KPO).

The fleet breaks down into 42 Solaris buses and 31 Irizar ie buses. The Irizar batch alone includes 16 articulated 18-metre vehicles and 15 standard 12-metre buses, destined for service in Sosnowiec, Świerklaniec, Katowice and Gliwice.

On the infrastructure side, the design choices are the interesting part. Most of the 45 chargers were installed at the operators' depots, while one charging point was deployed at the Kościuszki Street bus terminus in Będzin, and the mix includes both lower-power depot chargers and higher-power units intended for faster charging.

The metropolis's own transport authority confirms the split in plain terms: the infrastructure includes [lower-power chargers primarily intended for buses parked at depots, and high-power devices enabling faster recharging](https://transportgzm.pl/aktualnosci/73-nowe-autobusy-elektryczne-dla-gzm-zakonczyy-sie-odbiory-pojazdow).

We even have hardware specifics for part of the deployment. Reporting by Sustainable Bus notes that alongside its 31 buses, Irizar supplied and installed 20 depot chargers — eighteen dual 80 kW units (2×40 kW), one triple 120 kW charger (3×40 kW) and one 180 kW charger (3×60 kW) — including [the associated electrical infrastructure from design through commissioning](https://www.sustainable-bus.com/electric-bus/irizar-gzm-delivery-electric-buses-poland/).

That detail matters, because a "2×40 kW" unit is a single charger cabinet feeding two buses. One cabinet, two parked vehicles. This is exactly how you get more buses than chargers to work.

Why Every Bus Does Not Need Its Own Charger

The instinct to buy one charger per bus is expensive and usually wrong. A city bus spends a large share of every 24-hour cycle not driving — parked overnight, resting between shifts, or laying over at a terminus. Charging happens in those gaps.

Good electric bus depot charging works around vehicle idle time, not fleet size. The GZM ratio of about one charger per 1.6 buses works because of three things:

• Dwell time. Overnight, buses sit in the depot for 6–10 hours. A low-power charger can easily refill a battery in that window, so one charger can service one bus per night — but a single dual-output cabinet can serve two.
• Sequencing. Not every bus returns at the same minute. Vehicles arrive in waves, so a charger freed by one bus is immediately reused by the next.
• Split-power strategy. Slow chargers do the overnight bulk work cheaply; a few high-power units handle mid-shift top-ups and quick turnarounds.

This is the single most important lesson: your EV bus charger requirement is driven by battery size, daily kilometres, dwell time and charger power — not by fleet headcount alone. A depot of 30 short-route buses with big batteries may need far fewer chargers than a depot of 30 long-haul buses with small ones.

Overnight Depot Charging vs Daytime Fast Charging

There are two dominant charging philosophies behind any electric bus depot charging strategy, and good depots blend them.

Depot (overnight) charging

Buses return to the depot at night and charge slowly over several hours using lower-power CCS2 plug connections. This is the cheapest energy — off-peak tariffs, gentle on the battery, and it lets you run many chargers on a manageable grid connection. GZM's lower-power depot chargers do exactly this job.

Opportunity (fast) charging

Higher-power chargers — often pantograph systems mounted overhead — top up the battery in minutes during layovers at a terminus or interchange. That single unit GZM placed at the Będzin terminus is a textbook opportunity-charging point: it keeps buses in service without long returns to the depot.

The practical answer in the depot charger vs opportunity charger debate is rarely "one or the other." Most modern networks use plentiful slow depot chargers for the overnight bulk, plus a handful of fast chargers for flexibility and route insurance.

Electric Bus Depot Charging Design: The Real Constraints

Charger count is only half of a sound electric bus charging station design. The other half is the electrical and physical backbone behind the sockets.

Charger scheduling and load management

If all 45 chargers pull full power at once, the grid connection — and your electricity bill — explodes. Smart charging software staggers and throttles charging based on each bus's next departure. A vehicle leaving at 5 a.m. is prioritised; one leaving at 9 a.m. charges later and slower. This flattens the load curve and is why a depot can install more chargers than its peak power would otherwise allow.

Bus arrival and departure planning

Charging schedules must be built around the actual duty roster. Depot layout, parking bays and cable reach all follow from when each bus arrives, how depleted it is, and when it must leave fully charged.

Transformer redundancy and capacity

A single transformer failure should not strand an entire fleet. Depots serving critical routes typically design in transformer redundancy so charging continues even if one feeder drops out — a core part of any serious bus charging infrastructure planning exercise.

Demand charges and peak-load control

Commercial electricity bills include demand (kVA) charges tied to your highest 15-minute or 30-minute peak. Uncontrolled charging spikes that peak and inflates costs for the whole year. Load management, battery buffering and off-peak scheduling directly protect the operating budget.

Pantograph vs CCS2

CCS2 plug charging is standard for overnight depot use — lower power, lower cost, more units per rupee. Pantograph charging (roof-mounted or inverted mast) suits high-power opportunity charging where a bus must connect and disconnect automatically in seconds. GZM's mix of low- and high-power hardware reflects this division of labour.

Space planning, cable routing and fire safety

Buses are long, and articulated ones (like GZM's 18-metre vehicles) are longer still. Bay spacing, turning radii, overhead cable management and clearances must be designed before the first charger is bolted down. High-voltage DC cabinets and lithium batteries also demand thermal spacing, ventilation, detection and suppression systems as standard fire-safety practice.

Charger downtime and fleet-service risk

Fewer chargers than buses keeps electric bus depot charging efficient — until a charger fails. Redundancy, remote monitoring and fast maintenance contracts turn a potential service outage into a non-event. This is precisely why the split-power, shared-cabinet model is paired with robust service planning.

What This Means for Electric Bus Depots in India — and Himachal Pradesh

For an electric bus depot India planner, the GZM project is a useful benchmark rather than a fixed formula. A ratio near one charger per 1.6 buses is achievable when overnight dwell times are long and duty cycles are well understood.

Himachal Pradesh adds its own variables. Hilly terrain and cold winters increase energy consumption per kilometre, which shrinks effective range and can push the required electric bus charger capacity higher than on flat urban routes. Grid strength varies between valleys and towns, so transformer sizing and redundancy deserve extra attention. Depots in and around Shimla and other hill stations may also face tighter physical space, making compact dual-output cabinets and careful cable routing especially valuable.

At EVision India, we plan and build electric bus depot charging infrastructure exclusively across Himachal Pradesh, so depot design here accounts for gradient, altitude and local grid realities from day one. If you are scoping a fleet, our solutions and services teams size chargers around duty cycles, not guesswork, and our process covers everything from load study to commissioning. You can review available charging products or get in touch to plan a site survey.

Key Takeaways

• GZM deployed 73 buses with 45 chargers — about one charger per 1.6 buses, not one per bus.
• Dual-output cabinets, staggered dwell times and smart load management make that ratio work.
• Blend cheap overnight depot charging with a few high-power fast/pantograph points for flexibility.
• The correct charger ratio depends on battery size, daily kilometres, dwell time and charger power — never fleet size alone.
• Transformer redundancy, demand-charge control and fire safety are as important as the chargers themselves.

Frequently Asked Questions

How many chargers does an electric bus depot need?

Fewer than the number of buses, in most cases. Poland's GZM project used 45 chargers for 73 buses — roughly one per 1.6 vehicles. The right number depends on battery size, daily kilometres, dwell time and charger power, so it must be calculated from the duty roster, not the fleet count.

What is the difference between a depot charger and an opportunity charger?

A depot charger is typically a lower-power CCS2 unit that charges buses slowly overnight while parked. An opportunity charger is a higher-power unit — often a pantograph — that quickly tops up a bus during a short layover at a terminus. GZM used mostly depot chargers plus one terminus charging point.

Why does one charger serve more than one bus?

Many depot chargers are dual-output cabinets (for example, a 2×40 kW unit) that feed two parked buses from a single cabinet. Combined with staggered arrivals and long overnight dwell times, this lets one charger service multiple buses across a night.

Do electric bus depots in Himachal Pradesh need more chargers than flat cities?

Possibly. Hilly gradients and cold winters raise energy use per kilometre, reducing effective range. That can increase the required charger capacity or count, and it makes accurate load studies and transformer redundancy especially important in the state.

What causes high electricity costs at a bus charging depot?

Demand (kVA) charges tied to peak load are the main culprit. If many chargers draw full power simultaneously, the depot's peak spikes and inflates the bill. Smart scheduling, off-peak charging and load management keep that peak — and the cost — under control.

Sources

• electrive — GZM hands over 73 electric buses and 45 charging stations (25 July 2026)
• Transport GZM (official) — 73 new electric buses for GZM: vehicle acceptance completed
• Sustainable Bus — Irizar delivers 31 battery-electric buses to GZM in Poland