Electric vehicle (EV) chargers power home sedans, electric scooters, buses, and commercial fleets. Correct breaker size guarantees safety and electrical code compliance.
Depot building with DC fast chargers, breaker sizing is critical. We talk about breaker requirements for diverse EV chargers and charging stations. Learn more!
What Are the Types of EV Chargers and Charging Stations?
EV charging is very varied and charges personal vehicles, e-mobility devices (e.g., scooters and electric bicycles), electric buses, and commercial fleets.
Level 1 and Level 2 chargers usually operate on 208V (commercial) or 240V (residential) systems, while DC fast chargers and bus depots tend to need 480V 3-phase power. Knowing the facility’s voltage is the first step in choosing the correct breaker.
Level 1 Chargers (120V)
Level 1 chargers operate at 120 volts, usually drawing 12–16 amps. They are ideal for home use, charging standard EVs overnight, or refueling light e-mobility vehicles like electric scooters and bicycles.
They typically require 15A–20A breakers, which makes them simple to install in residential or small-scale e-mobility centers.
Level 2 Chargers (240V)
Level 2 chargers, which operate at 240 volts, deliver 16–80 amps of high-speed charging. They are common in residences, offices, and commercial spaces, like e-mobility charging stations for bicycles or a few cars. Breaker sizes would range from 20A to 100A, depending on the charger amperage.
DC Fast Charging Stations (200–1000V DC)
DC fast chargers, with 50kW–600kW output, are used for commercial applications, such as public charging stations, bus stops, and fleet depots.
They use 480V 3-phase power (AC input) and require high-amperage breakers (100A–400A). These are required for the rapid charging of electric buses and heavy-duty vehicles.
Specialized Chargers
- E-Mobility: Low-power chargers (10A–20A) used for electric scooters and bicycles, commonly in urban charging stations.
- Electric Buses: DC high-power chargers (150kW–600kW) for bus terminals, requiring heavy-duty breakers (e.g., 450A for 300kW).
- Commercial Fleets: Multi-unit Level 2 or DC chargers for delivery trucks, taxis, or ride-sharing cars, with scalable installations.
What Size Breaker for EV Chargers & Charging Stations?
Before the selection, you can first read what is a circuit breaker to get a deeper understanding. Choosing the correct size of circuit breakers enables your EV charger to operate safely and in compliance with NEC Article 625, wherein breakers are required to be 125% of the continuous load of the charger.
The following are guidelines on breaker sizes for various chargers, with a specific focus on commercial DC fast chargers and bus depots.
NEC Rule for Continuous Loads
EV charging stations are classified as constant loads, operating for three or more hours. The NEC calls for a 125% breaker size of the charger amperage to prevent overheating. A sample would be a 40A charger requiring a 50A breaker (40 × 1.25 = 50).
Breaker Sizes by Charger Type
| Charger Type | Amperage | Breaker Size | Voltage |
| E-Mobility (Scooters/Bikes) | 10A–16A | 15A–20A | 120V |
| Level 1 | 16A | 20A | 120V |
| Level 2 | 32A / 40A / 80A | 40A / 50A / 100A | 208V/240V |
| DC Fast Charger | 60A / 180A / 420A | 75A / 225A / 500A | 480V 3-phase |
| Electric Bus Charger | 360A (300kW) | 450A | 480V 3-phase |
- E-Mobility: A 12A scooter charger needs a 15A breaker (12 × 1.25 = 15).
- Level 1: A 16A home charger requires a 20A breaker.
- Level 2: A 40A workplace charger needs a 50A breaker.
- DC Fast Chargers: A 150kW station (~180A at 480V) requires a 225A breaker.
- Electric Buses: A 300kW bus charger (~360A) needs a 450A breaker.
Panel Load Calculations
Before installation, verify your electrical panel capacity. Multi-unit installations like bus depots with 10+ DC chargers have high-load calculations. A 300kW bus charger will demand 450A, which may need a separate subpanel or transformer. Verify with a licensed electrician for capacity checks, especially for commercial installations.
There is another choice: GFCI circuit breaker. Ground Fault Circuit Interrupter (GFCI) breakers must be installed on certain Level 2 chargers (per 2023 NEC) but need not be on DC fast chargers, which are built differently. Double-check local code requirements.
What Wire Size for EV Chargers & Charging Stations?
Wiring is hardly second to breaker sizing in ensuring safe EV charger installations. Wire size depends on breaker, circuit length, and charger type, with commercial DC chargers requiring heavy-gauge wiring.
Wire Size by Breaker
- E-Mobility (Scooters/Bikes): 14–12 AWG copper for 15A–20A breakers.
- Level 1: 12 AWG copper for 20A breakers.
- Level 2: 6 AWG copper for 50A breakers; 2 AWG copper for 100A breakers.
- DC Fast Chargers/Electric Buses: 2/0 AWG copper for 225A breakers; 500 kcmil copper for 500A breakers.
Conduit and Circuit Length
High-amperage DC chargers or longer circuits require larger conduits to accommodate wiring. A 300kW bus charger, for example, may need 4-inch conduits for 500 kcmil wires, especially in commercial settings.
Dedicated Circuits
All EV charging stations require individual circuits to prevent overloading. The EV charging station components are necessary and helpful. The dedicated circuit is crucial for multi-unit installations, such as fleet facilities with 10+ DC charging stations, to ensure stable power.
3-Phase Power for DC Charging Stations
Bus terminals and DC fast charging stations typically use 480V 3-phase power, which requires special wire and transformers. Contact your utility company to confirm 3-phase availability, especially for big projects.
Regional Codes
Local regulations and regional codes, such as California’s Title 24, can have additional requirements for commercial installations. Please check with your local jurisdiction to comply.
Installation of EV Charger & Charging Station Breakers
What Makes the Installation Complex?
- Charger Type: Level 1, electric scooter, E-bike chargers are simpler; DC fast and bus chargers are complex.
- Electrical Infrastructure: Home chargers may utilize existing panels, but commercial installations need 3-phase power or transformers.
- Installation Scope: Stand-alone home units are simple; bus terminals that serve multiple units require significant planning.
| Charger Type | Complexity | Equipment Needs | Infrastructure Upgrades | Professional Expertise |
| E-Mobility (Scooters/Bikes) | Low | Small breaker, light wiring | Minimal | Optional |
| Level 1 | Low | Basic breaker, wiring | Minimal (existing circuits) | Optional |
| Level 2 | Medium | Larger breaker, conduit | Possible panel upgrade | Recommended |
| DC Fast Charger (Commercial) | High | Heavy-duty breaker, 3-phase wiring | Likely transformer, panel upgrades | Mandatory |
| Electric Bus Charger | Very High | High-amperage breaker, heavy wiring | Transformer, 3-phase upgrades | Mandatory |
More Installation Tips
1. For DIY
Chargers for scooters, bikes, or home EVs with pre-installed circuits are good for DIY, which only calls for a rudimentary knowledge of electrical work.
Note: Safety. Always get permits and inspections to meet local codes.
2. Need Professionals
Level 2 charger installation often requires professionals due to larger breakers and potential panel upgrades. Professionals know better about how to replace a circuit breaker or install it in EV charging stations.
DC fast charger and bus charger installation also need electricians. Mandatory for 3-phase power, heavy wiring, and multi-unit installations in bus depots or fleet hubs.
3. Commercial Challenges
Bus depots and fleet stations require specialized equipment, utility permits, and compliance with strict codes. A 300kW bus charger, for example, needs a 450A breaker and 3-phase equipment, requiring certified electricians.
4. Safety Tips
Secure permits, organize inspections, and follow NEC standards. Commercial projects may require utility approvals for 3-phase power.
NEC Requirements for EV Chargers & Charging Stations
Compliance with the National Electrical Code (NEC) and regional standards ensures safe installations, especially for commercial DC and bus chargers. Below, we summarize key requirements.
NEC Article 625 (2023 Updates)
Article 625 governs EV chargers with the following requirements:
- 125% breaker sizing of continuous load.
- Exclusive circuits for all chargers.
- Grounding and overcurrent protection for DC and bus chargers (e.g., 450A breakers for 300kW).
GFCI Requirements
GFCI breakers are required for some Level 2 chargers but are optional for DC fast chargers, depending on local codes.
3-Phase Power Standards
DC fast chargers and bus depots using 480V 3-phase power must follow NEC rules for high-amperage wiring and transformers. Coordinate with utilities for compliance.
Regional Codes & International Standards
California (Title 24) and other states have additional commercial installation requirements, e.g., energy efficiency regulations. Check local codes for multi-unit installations.
Global e-mobility and bus charger installations can be IEC compliant. Verify local code for foreign projects.
Wrapping Up
Selecting the right size of breaker for EV chargers from e-mobility scooters to electric buses offers efficiency and safety. 15A–20A breakers are required for E-mobility and Level 1 chargers, 40A–100A for Level 2 chargers, and for DC fast charging for fleets and buses, use 225A–500A.
Commercial application, including bus depots, requires 3-phase power, heavy wire, and expertise. Always meet NEC and local regulations, especially multi-unit applications.
FAQs About EV Charger & Charging Station Breakers
What size breaker for a 300kW electric bus charger?
A 300kW bus charger (about 360A at 480V 3-phase) requires a 450A breaker, as per NEC’s 125% rule.
What breaker for an e-mobility scooter charging station?
A 12A scooter charger requires a 15A breaker, compatible with 120V circuits for city centers.
Do DC chargers need 3-phase power?
Yes, the majority of DC fast chargers and bus chargers demand 480V 3-phase power for high-power charging.
What size breaker for level 2 EV chargers?
The required breaker size depends on the charger’s amperage.
For example:
- A 32A charger needs a 40A breaker
- A 40A charger needs a 50A breaker
- An 80A charger needs a 100A breaker
This follows the NEC 125% rule for continuous loads (amperage × 1.25 = breaker size).
Are GFCI breakers required for EV chargers?
GFCI (Ground Fault Circuit Interrupter) breakers are required for many Level 2 EV chargers, depending on location and product design. DC fast chargers are generally exempt due to their built-in safety systems. (Also remember to check your local codes!)
