Level 2 Charging Sized for Your Panel

The load calculation comes first

Before anything can be sized, we have to know what your service can carry. NEC 220.83 gives a calculation method for adding load to an existing dwelling. NEC 220.87 gives a second method based on measured maximum demand, using the highest fifteen-minute demand recorded over the previous year multiplied by 125 percent. Where good utility interval data is available, 220.87 frequently shows more available capacity than the calculated method does.

This matters because the answer changes the price of the job by thousands of dollars. A 200 amp service in a newer West Richland or south Kennewick house often has room for a 60 amp circuit without touching the panel. A 1950s Richland house on 100 amp service with an electric range and dryer may not, and then the conversation turns to a service upgrade or a load management device. We run the numbers before quoting, not after the work has started.

Circuit sizing and what the amperage means

EV charging is a continuous load, so the circuit gets sized at 125 percent of the charger output under NEC 625.41. That is why a 40 amp breaker supports 32 amps of charging, a 50 amp breaker supports 40 amps, and a 60 amp breaker supports 48 amps. Charger amperage is what determines charging speed. Most Level 2 units are adjustable, so a 48 amp unit can be commissioned at 32 amps on a 40 amp circuit when that is what the service supports.

Faster is not automatically better. A 32 amp charger adds roughly 25 to 30 miles of range per hour for a typical EV, which fully recovers a normal Tri-Cities commute in a couple of hours overnight. The case for 48 amps is a large battery, a long daily drive, or two vehicles sharing one unit. Paying for a service upgrade to reach 48 amps when 32 already covers your driving is money that could have stayed in your pocket.

Plug-in or hardwired

A NEMA 14-50 receptacle lets you plug in a portable charging cord, which is convenient and makes the unit easy to take with you or replace later. It comes with rules. The receptacle circuit requires GFCI protection under current code, the receptacle itself should be an industrial-grade device rather than the cheapest one on the shelf, and the circuit tops out at 40 amps of charging on a 50 amp breaker. Cheap 14-50 receptacles overheating under continuous load is a documented problem.

Hardwiring removes the receptacle as a failure point, and it is required above 48 amps. It also mounts more cleanly outdoors and generally holds up better through years of daily plugging and unplugging. The tradeoff is that swapping the unit later becomes an electrician visit instead of unplugging a cord. For a permanent home charger in a garage or on an exterior wall, we usually recommend hardwired unless you have a specific reason to want the plug.

Permits, inspection and incentives

EV charger installation is permitted electrical work. In most of Benton and Franklin County the permit and inspection go through Washington L&I, and the City of Richland runs its own electrical inspection program for work inside city limits. Either way we pull the permit and meet the inspector. Skipping the permit creates a problem at resale, can complicate an insurance claim, and means nobody independent ever verified a 48 amp continuous circuit in your attached garage.

On incentives, the honest answer is to check current programs before counting on anything. Federal tax credit rules for EV charging equipment have changed recently, and utility programs through Benton PUD and Franklin PUD come and go with their own eligibility rules and application steps. We will not quote you a credit amount or promise a rebate. Check the current federal guidance and your utility program page, and apply before the install if the program requires it.