EV Home Charging Issues

Problems that can arise and how to protect your home.

For the new EV or Hybrid owner, a big concern is charging – for good reason. Car manufacturers and sales staff don’t always go into detail on this point, and the information is usually buried deep in the owner’s manual. We hear that some suggest a standard 120-volt electrical outlet will be all it takes.

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1. Not all 120-volt outlets are created equal.

In many homes, especially older homes, the garage outlet is on light-weight wire (14-guage), on a lightweight circuit breaker (15-amp), and on a circuit shared with other outlets, lights, etc. This is a recipe for problems, including possible electrical fires.
Here’s a picture of one such outlet, from the garage of a relatively new home, after about a week of EV charging.

At an absolute minimum, the “standard” outlet needs to be on a dedicated (no sharing) 20-amp circuit.

2. EV’s don’t charge very fast on standard 120-volt circuits.

It’s usually somewhere in the owner’s manual. To get reasonable charge times (in hours rather than days), EV’s generally require a high-power 240-volt circuit, like you’d use for an electric clothes dryer or an electric stove.

And some cars (not all) require a special wall charging unit in order to use the 240-volt power.

3. EV’s are NOT like electric stoves. Or dryers.

“Non-Continuous” Loads: With a typical electric stove, there might be one burner on, or two, maybe even three, at a time. You might turn on the oven, you might not. You might have the oven AND a burner on. Or not. And even with the oven, its heating elements turn on and off, according to the temperature settings.

The amount of electricity being used fluctuates.

The National Electrical Code (NEC) classifies this as a non-continuous load. Although the stove may be on a 50-amp circuit, it’s extremely rare that it gets close to drawing that full amount, and even then it’s intermittent.

“Continuous” Loads: Electric cars are different. When you plug a car into a charger that’s on, say, a 50-amp circuit, it starts charging at a solid 42-amp rate, typically, and stays there — for hours.

The amount of electricity being used is constant.

The NEC calls this a continuous load, and the wiring requirements are very different. In addition, a 40-amp continuous load can play havoc with your home’s electrical system if, for example, you have only a 100-amp service to begin with. That’s small by today’s standards, but 100 amps was the standard not that long ago.

Fast, safe charging is the goal. The big factors are:

  • the car (size, model, charging requirements)
  • the location (garage – attached, detached, distance from panel, etc)
  • the electrical service (capacity and condition)

Click here for more about Fast, Safe EV charging installations.

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