AC charging vs. DC charging: The optimal charging strategy for reducing TCO for electric fleets
AC charging vs. DC charging: The optimal charging strategy for reducing TCO for electric fleets
The decision between AC charging and DC charging is fundamental to the profitability of your electric fleet. It not only determines the downtime of your vehicles, but also directly affects your total cost of ownership (TCO).
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The topic briefly and concisely
AC charging at up to 22 kW is the most economical solution for planned overnight charging at the depot and is gentler on the battery.
165 kW DC charging minimises downtime and maximises vehicle availability on unpredictable or long routes.
An intelligent mix of AC and DC charging infrastructure, managed through load management, is the key to reducing TCO.
The electrification of commercial vehicle fleets is essential to meet the Clean Vehicles Directive (CVD). However, the central challenge for 9 out of 10 fleet managers is the development of efficient charging infrastructure. The choice between alternating current (AC) and direct current (DC) charging forms the foundation of any successful strategy. An incorrect approach can significantly increase operating costs and restrict vehicle availability. HEERO analyses the differences and outlines a pragmatic path that secures TCO advantages and operational stability for your converted or new e-buses.
Technical Fundamentals: The Key Difference Between AC and DC Charging
The electricity from the public grid is usually alternating current (AC). However, a vehicle battery can only store and deliver direct current (DC). During AC charging, an on-board charger installed in the vehicle, the so-called On-Board-Charger (OBC), converts the alternating current into direct current. The charging power is limited by the OBC to 11 or 22 kW. This is the most efficient method for 90% of depot charging operations.
During DC charging, this conversion takes place in the charging station itself. The direct current flows directly into the vehicle battery and bypasses the vehicle's OBC. This enables significantly higher charging powers, such as 165 kW in a HEERO eDrive system. This method reduces charging time by over 80% compared with AC charging. The choice of technology therefore depends directly on the application.
AC charging at the depot: the foundation for predictable, low operating costs
For fleet vehicles that are parked overnight or for several hours in the same location, AC charging at 22 kW is the most economical solution. The installation costs for AC wallboxes are significantly lower than for DC fast-charging stations. In addition, the grid load is lower, which avoids costly load peaks and keeps grid charges stable. A HEERO with a 137 kWh battery is fully charged in around 6 hours.
This predictable charging process can be ideally integrated into the overnight operational breaks. AC charging also protects the battery, as the charging power is lower. Gentle charging can positively influence the battery's service life, the so-called State of Health. The following points speak in favour of AC charging in the depot:
Lower investment costs in the charging infrastructure.
Lower installation and grid connection costs.
Optimal use of overnight parked periods of 8-10 hours.
Protection of the vehicle battery through lower charging power.
Easy integration into a load management system to avoid power peaks.
This method forms the backbone of a cost-efficient electrification strategy and is complemented by targeted DC charging.
DC fast charging: Maximum operational readiness for dynamic routes
DC charging is indispensable when vehicles need to be ready for use again quickly. With a charging capacity of 165 kW, a HEERO can charge its 137 kWh battery from 20% to 80% in just 30-40 minutes. This is crucial for vehicles operating in multiple shifts or on unpredictable routes, where long idle times are not an option. Reducing downtime by several hours significantly increases vehicle utilisation.
Although the investment in DC charging infrastructure is higher, it pays off through the increased operational flexibility. A single DC charging point can serve several vehicles throughout the day and thus help absorb bottlenecks. The knowledge of the optimal charging time from 20 to 80 percent is crucial for route planning. However, the higher requirements for the grid connection require careful planning, which HEERO covers as part of depot charging consultancy with its partners from an expert pool.
The hybrid strategy: TCO optimisation through an intelligent charging mix
For most fleets, neither a purely AC nor a purely DC strategy is optimal. Combining both technologies delivers the best TCO. A typical fleet equips 80% of its parking spaces with 22 kW AC wallboxes for basic overnight charging. This is supplemented by a few strategically placed DC fast chargers for unplanned deployments or quick top-ups during the day. This approach can significantly reduce infrastructure costs compared with a purely DC solution.
Intelligent load management is essential here. It dynamically distributes the available grid capacity across the charging vehicles and prioritises according to departure time and the required State of Charge (SoC). This avoids expensive load peaks and makes optimal use of the grid connection. HEERO advises fleet operators, together with its partners, on the design of such a tailored charging infrastructure. This means electrification becomes not only legally compliant, but also a tangible economic advantage.
More useful links
The NOW GmbH offers a comprehensive guide to electromobility in fleets.
The Bundesnetzagentur provides detailed information on electromobility.
A recent study by NOW GmbH examines the development of charging infrastructure for the years 2025 to 2030.
The National Charging Infrastructure Centre provides information on current funding programmes in the field of electromobility.
The Research Centre for Energy Economics e.V. (FFE) provides a detailed document on electromobility for fleet operators.
FAQ
What is better for my fleet: AC or DC charging?
Neither. The optimal strategy for 90% of fleets is a mix: AC charging as the foundation in the depot for planned overnight charging, and DC charging for operational peaks during the day. This optimises costs and flexibility.
How does DC rapid charging affect battery lifespan?
Frequent DC charging can place greater thermal and chemical stress on the battery than AC charging. Modern battery management systems, as used in HEERO vehicles, however actively control the process to minimise the impact on the <a href="/news-presse/soh-state-of-health">State of Health</a> and ensure a long service life.
What grid connection capacity do I need for DC chargers?
A 165 kW DC charger requires substantial connection capacity, often over 150 kVA. This calls for early assessment and planning with the grid operator to avoid bottlenecks or costly upgrades. Our depot consulting supports you throughout this process.
How long does a full charge take with 22 kW AC?
Charging a 137 kWh battery from 0 to 100% with 22 kW charging power takes around 7 hours in purely mathematical terms. This fits perfectly into an overnight window of 8-10 hours, ensuring the vehicles are fully ready for use each morning.
Why is the distinction between AC and DC charging relevant to CVD compliance?
An efficient charging strategy ensures the daily operational readiness of your electric fleet. This is the only way to reliably and cost-effectively meet the statutory procurement targets of the Clean Vehicles Directive for commercial vehicles in day-to-day operations.
Does HEERO also offer advice on charging infrastructure?
Yes, our experts assess your current situation, analyse your operating processes with our partners and create a tailored concept for your depot charging infrastructure. This includes selecting the right AC/DC mix and implementing load management to optimise TCO.
