Why is a 7kW EV charger 32A, but a 22kW charger is 16A?

Let’s talk about the conclusion first

A 7kW electric vehicle charger usually uses a 220-240V power supply voltage, which consumes about 32A of current. 22kW chargers are typically designed for higher 380-400V three-phase power supplies and require only 16A to achieve 22kW.

Power Equation

The power equation demonstrates the relationship between power, voltage and current. Power (in watts) is equal to voltage (in volts) multiplied by current (in amps). So for a given power level, higher voltage means lower current, and vice versa. This explains how a 7kW and 22kW EV charger can have different amperage ratings.

Voltage Standards

There are different voltage standards around the world that impact EV charger power ratings. In the US, residential voltage is usually 220-240V, while in Europe residential voltage is often 380-400V. Since amperage is lower at higher voltages, European EV chargers with the same power rating will have lower amp current.

Charger Power Ratings

EV charger power ratings refer to the maximum power the charger can provide. Common levels are 3.3kW, 7kW, 11kW, 22kW or higher. Higher power allows faster charging, but also requires sufficient electrical supply and infrastructure. Comparing a 7kW and 22kW charger demonstrates why current draw may differ.

Charger Current Ratings

While EV charger power is rated in kilowatts (kW), the current draw is what determines required circuit capacity and wiring. A 7kW charger may be rated at 32A, while a 22kW charger is only 16A. This seeming contradiction is explained by differences in voltage at which the chargers operate.

Higher Voltage Means Lower Current

For a given power level (watts), higher voltage results in lower current (amps). This is according to the power equation that states power equals voltage multiplied by current. Therefore, the same 7kW charger will draw much less current at higher voltage.

Comparing 7kW and 22kW Chargers

A 7kW EV charger often uses 220-240V supply voltage, at which it will draw about 32A of current. A 22kW charger is typically designed for much higher 380-400V three phase supply, at which it only needs 16A to achieve 22kW. The higher voltage allows lower current.

For charger manufacturers, electrical performance is only one side of the product; the consistency of custom aluminum or stainless steel parts also affects assembly, durability, and outdoor reliability.

Importance of Voltage for EVs

Voltage is an important specification for EV charging infrastructure. Higher voltages allow lower charging currents, reduce wiring requirements and electrical losses. This enables faster charging at higher power levels. Comparing chargers demonstrates interactions between voltage, power and current.

220V vs 380V Charging

220V is the typical single phase voltage in the US, while Europe more commonly uses 380V three phase electrical supply. For the same charger power rating, 380V supply means lower amperage draw. However infrastructure costs are higher with supporting 380V charging stations.

Charger Amperage Limits

EV chargers have maximum current ratings that must align with electrical panel and wiring capacities. For home charging, a 240V 32A circuit is common, limiting chargers to 7.2kW. Public chargers use higher voltages and lower amperage limits to provide more power while remaining within infrastructure constraints.

Cabling and Breaker Considerations

The size of electrical wiring and circuit breakers must match expected loads. An EV charger’s amperage rating determines cabling and breakers needed according to electrical code. Higher volts and lower amps allows more power to be delivered within existing infrastructure constraints.

FAQ

Here are 5 common FAQs about EV charger power and current ratings:

Q: Why is a 7kW charger 32A but a 22kW only 16A?

A: Higher voltage for 22kW charger means lower current.

Q: What voltage are most level 2 chargers?

A: 240 volts.

Q: Can I install a high-powered charger at home?

A: Special wiring and permits often required.

Q: Is a 32A circuit enough for fast charging?

A: 32A only supports up to 7kW.

Q: Which is better – more power or more current?

A: Depends on infrastructure constraints.