Centralized vs. Distributed Power Architecture for Fleet Charging Depots

# Centralized vs. Distributed Power Architecture for Fleet Charging Depots

Every fleet charging depot makes an invisible architectural choice that shapes its cost, reliability, and scalability for the next 15 years. It's not about which charger brand you buy. It's about how you distribute power from the transformer to the parking spots.

There are two ways to do it: centralized (a few large power cabinets serving many dispensers) and distributed (individual chargers at each parking position). The choice affects your upfront cost, your maintenance workflow, your expansion path, and your resilience to failure.

Centralized Architecture

A centralized system places a few high-power cabinets — often 300-960 kW each — in a central equipment room or pad. These cabinets distribute DC power to multiple dispensers at individual parking spots through DC bus bars or long cable runs.

Example: Two 480 kW central cabinets serving 16 dispensers (8 parking positions each). Each dispenser is a pedestal with a cable and connector but no power conversion — the conversion happens in the central cabinet.

Advantages: - Fewer power conversion units to maintain. Two cabinets = two sets of power electronics to monitor. - Lower cost per kW at scale because you're buying fewer, larger power stacks. - Centralized cooling and electrical protection in a controlled environment. - Better for sites where parking positions are tightly packed and a cabinet at every spot isn't feasible.

Disadvantages: - Long DC cable runs between the central cabinet and dispensers. Above roughly 100 feet, DC voltage drop becomes significant and cable cost rises fast. Liquid cooling may be required. - Single point of failure. One central cabinet failure disables every dispenser connected to it — potentially 8+ parking spots. - Expansion requires adding another central cabinet with its own electrical feed, pad, and DC distribution. - Less flexibility to mix charger types. If you need 350 kW at some spots and 120 kW at others, the central cabinet must be sized for the highest power requirement.

Distributed Architecture

A distributed system puts a self-contained charger at every parking position. Each unit has its own power conversion, control, cooling, and connector. The chargers share a common AC electrical feed from the transformer.

Example: 16 individual 120-240 kW DC chargers, each at its own parking spot. Each unit operates independently.

Advantages: - No single point of failure. One charger failure affects one parking spot. - Short cable runs. The charger is at the parking spot, so DC cables are 10-15 feet, not 100+ feet. No voltage drop issues. - Mixed power levels. You can put 240 kW chargers at high-turnover spots and 60 kW chargers at overnight spots — each unit is independent. - Incremental expansion. Add chargers one at a time as the fleet grows, without sizing a central cabinet for future capacity. - Modular redundancy within each unit. A distributed modular charger can still use hot-swappable power modules for internal redundancy.

Disadvantages: - More individual units to maintain. 16 distributed chargers = 16 sets of power electronics, cooling fans, and controllers to monitor. - Higher cost per kW at small scale. Below roughly 6-8 chargers, the per-unit cost of distributed chargers may exceed the per-dispenser cost of a centralized system. - Larger equipment footprint at each parking position.

The Comparison Table

The Real-World Tradeoff

A 50-spot bus depot with identical parking positions and identical bus types benefits from centralization. The power requirement is uniform, the parking is dense, and a central equipment room makes sense.

A 30-spot mixed-fleet depot with delivery vans (AC), medium-duty trucks (120 kW DC), and heavy-duty trucks (240 kW DC) benefits from distribution. Each spot gets the right charger for the vehicle.

The crossover point — where distributed becomes cheaper or more practical than centralized — is roughly 8-12 ports with mixed power requirements, or 20+ ports with uniform requirements. Below that, centralized is usually cheaper. Above that, the flexibility and reliability of distributed architecture start to dominate.

What the Manufacturers Don't Tell You

DC cable cost is nonlinear. A 150-foot DC cable for a 350 kW charger can cost $3,000-5,000 and requires liquid cooling. A 15-foot cable for the same charger costs $500-800 and is air-cooled. In a centralized system with 16 dispensers, the cable cost alone can add $40,000-80,000 to the project — often erasing the upfront savings from buying fewer cabinets.

Voltage drop limits parking layout. DC voltage drop is roughly 1-2% per 100 feet at 350 kW. If your farthest dispenser is 200 feet from the central cabinet, you're losing 2-4% efficiency and may need to oversize the cables. This constrains where you can put parking spots relative to the equipment pad.

Maintenance access changes everything. A centralized cabinet in an indoor equipment room is easier to service than distributed chargers exposed to weather, dust, and vehicle impact. But a failed central cabinet takes 8+ spots offline while a distributed charger takes one. The tradeoff is between mean time to repair (centralized wins) and blast radius of failure (distributed wins).

A Hybrid Approach

Some large depots combine both architectures: centralized high-power cabinets for the core charging lanes where buses or trucks need uniform 240 kW, and distributed chargers at the perimeter for maintenance bays, visitor charging, or mixed-fleet spots.

FBK POWER's Split-Type DC Charging Cabinet supports both architectures. In centralized mode, a single master cabinet powers multiple satellite dispensers. In distributed mode, each cabinet operates independently at its own parking position. The same hardware serves either topology — you choose based on your site layout, not the charger's limitations.

How to Decide

Answer these questions for your site:

1. How uniform are your parking positions? If every spot needs the same power level, centralization gains. If power needs vary, distribution gains.

2. How far apart are your parking spots? If spots are more than 80 feet from a feasible equipment pad, DC cable costs tilt the decision toward distribution.

3. How critical is single-point failure risk? If a central cabinet failure stranding 8 trucks for a day is unacceptable, distribute. If you have spare parking capacity to absorb a failure, centralize.

4. How will your fleet grow? If you're adding 5 vehicles a year for 10 years, distributed incremental expansion is easier. If you're deploying 50 vehicles in one batch and won't grow much, centralize once and move on.

5. What's your maintenance staffing? If you have 1-2 technicians managing 30+ chargers, the fewer-units-to-monitor advantage of centralized matters. If you have a dedicated EV maintenance team, distributed redundancy is worth the monitoring overhead.

Bottom Line

For most fleet depots with 10+ vehicles, mixed power requirements, and growth plans, distributed modular architecture is the safer bet. It costs slightly more upfront but avoids the catastrophic failure mode of a central cabinet taking down a whole charging lane. For large, uniform depots (e.g., 50 identical transit buses), centralized with DC distribution can be more cost-effective — provided you size the cable runs correctly and have a maintenance plan for the central cabinets.

The worst approach is picking an architecture based on the first year's cost and discovering in year three that you can't expand it without ripping out concrete.

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FBK POWER's modular DC fast charging cabinets support centralized, distributed, and hybrid architectures. Contact our team for a site-specific power architecture analysis, or request a quote for modular charging hardware that adapts to your depot layout.

References

• NREL (2024). Electric Vehicle Charging Infrastructure for Fleet Depots. National Renewable Energy Laboratory.
• CharIN (2026). Megawatt Charging System Cable Standards. https://charin.global