Demand Charges Are Killing Your Fleet Charging ROI — How Load Management Fixes It

# Demand Charges Are Killing Your Fleet Charging ROI — Here's How to Fix It

If you run a fleet depot with more than a handful of DC chargers, your electricity bill has a line item that keeps your CFO up at night. It's not the kWh charge — it's the demand charge. And if you're not managing it, you're leaving thousands of dollars a month on the table.

What Demand Charges Are, in Plain English

Your utility doesn't just charge you for how much electricity you use (kWh). It also charges you for how fast you pull it (kW) — specifically, the highest 15-minute average during the billing period. This is the demand charge, and it's designed to make you pay for the grid capacity you require even if you only use it for a few minutes a month.

Here's why it matters for fleet charging. A 150 kW DC fast charger running for 15 minutes triggers a 150 kW demand spike. Six of them running simultaneously: 900 kW. At a rate of $15/kW — typical for commercial customers in many U.S. markets — that single 15-minute window costs you $13,500. That's before you pay a single cent for the actual electricity.

Over a year: $126,000. Over 10 years: $1.26 million. That's the cost of not managing your load.

How Load Management Fixes It

Load management caps the total power draw at your site. Instead of letting six chargers each pull 150 kW simultaneously and blow through your demand limit, the system distributes available power based on:

• How much charge each vehicle actually needs
• When each vehicle needs to be ready
• The site's demand cap
• Time-of-use rates

Here's how it works for a real fleet. A depot with 40 delivery vans and 8 x 120 kW DC chargers has a 960 kW nameplate total. With a 300 kW demand cap, the load management system ensures total site draw never exceeds 300 kW. Vehicles that are parked for 10 hours don't need 120 kW — they can take 40 kW and still reach full charge well before morning. Vehicles with tighter turnaround windows get priority.

CALSTART's modeling found that managed charging saves a typical fleet 37% on energy costs compared to unmanaged charging — from $0.436/mile to $0.290/mile for Class 8 short-haul electric trucks [CALSTART, 2024].

Static vs. Dynamic vs. Elastic Load Balancing

Not all load management is equal.

Static load balancing pre-assigns fixed power limits to each charger. Simple, cheap, inflexible. If you set every charger to 40 kW, you'll never exceed 320 kW for eight chargers — but you also can't give 120 kW to a truck that needs it quickly.

Dynamic load balancing reallocates power in real time based on demand. The system monitors each vehicle's state of charge, requested power, and departure time, then adjusts charger output continuously.

Elastic load balancing extends dynamic management by responding to external signals: utility rates, building energy use, on-site solar generation, and grid events. This is where the biggest savings live. For a deep dive, see our guide on elastic load balancing for EV charging.

OCPP Makes It Work

Load management requires communication between the chargers, the site controller, and the backend. This is where OCPP (Open Charge Point Protocol) matters. Changers that speak OCPP can receive real-time power limits from a central controller and report their actual output, state of charge, and connector status.

Without OCPP, you're managing chargers one at a time through their individual interfaces — impossible to scale past a handful of units. With OCPP, the entire site operates as a single energy asset. For more on protocol selection, see our OCPP 1.6 vs 2.0.1 comparison.

Utility Rate Design: What to Ask For

Before you sign an interconnection agreement, talk to your utility about rate options. Many offer:

• Time-of-use (TOU) rates: Lower $/kWh during off-peak hours. Pair this with overnight depot charging and your energy cost drops substantially.
• Demand charge alternatives: Some utilities offer rates with lower demand charges and higher kWh charges — better for high-load-factor operations like fleet depots.
• EV-specific tariffs: A growing number of utilities have created dedicated rates for EV charging. These typically feature lower off-peak rates and may include demand charge holidays for new loads.
• Interruptible service: Accept occasional curtailment in exchange for significantly lower rates.

PG&E's commercial EV rate (BEV-1) is one example: separate pricing for on-peak and off-peak, with the off-peak rate roughly 60% lower [PG&E, 2026]. For a depot that does all its charging between 10 PM and 6 AM, that rate structure can cut annual electricity costs nearly in half compared to a standard commercial rate.

When Battery Storage Makes Sense

A battery energy storage system (BESS) can eliminate demand charges entirely for a subset of your charging load. The battery charges slowly overnight at low power, then discharges rapidly to vehicles during high-demand windows — without pulling from the grid.

A 500 kW / 1 MWh BESS costs roughly $300,000-500,000 installed. If demand charges alone are costing you $126,000/year, the payback is 3-4 years. After that, the battery is earning its keep. For a detailed analysis, see our guide on battery energy storage for EV charging sites.

The Overlooked Benefit: Grid Interconnection

Load management doesn't just save money — it can make your project possible. If your depot site has 500 kW of available utility capacity and your unmanaged charger nameplate is 960 kW, the utility will require a transformer upgrade that could take 18 months and cost $300,000. With a 300 kW demand cap enforced by load management, you can proceed with the existing service.

The ICCT recommends this approach explicitly: size the site for managed load, not nameplate [ICCT, 2024]. It's the difference between a project that starts in 2026 and one that starts in 2028.

Getting Started

1. Pull your utility's commercial rate tariff. Find the demand charge rate ($/kW).
2. Model your fleet's charging pattern: how many vehicles plug in, when, for how long, at what power level.
3. Calculate your unmanaged demand charge exposure.
4. Compare managed scenarios: 30%, 50%, and 70% of nameplate.
5. If the annual savings exceed the cost of a load management system (typically $5,000-20,000 one-time plus minimal recurring), buy it.

For most fleets with more than four DC fast chargers, the system pays for itself in under a year on demand charge savings alone. The 37% energy cost reduction that CALSTART documented? That's on top.

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FBK POWER's modular DC fast chargers support OCPP-based dynamic and elastic load management out of the box. Contact our team to discuss load management for your depot, or request a quote for chargers with integrated energy management.

References

• CALSTART (2024). Manage the Charging for Your MHD Electric Fleet and Save Money. https://calstart.org
• ICCT (2024). Powering Seattle Fleets. https://theicct.org
• PG&E (2026). Electric Vehicle Rate Plans. https://www.pge.com