Level 2 EV Charger on a 100-Amp Panel: Load Calc, Load Management or Upgrade?

How an electrician decides if a charger fits

Under the 2023 NEC, used in Washington and in Oregon until October 1, 2026, EV charging equipment is counted in a load calculation at 7,200 watts or its nameplate rating, whichever is larger (220.57). That goes into the house's existing load calculation along with everything else, and the result has to fit the service.

For an existing house there are two ways to get the starting number. The first is a calculation from what is installed: floor area, kitchen and laundry circuits, and every fixed appliance, with demand factors applied. The second is often more favorable: the code (220.87) allows using the highest 15-minute demand from the last 12 months of utility data, multiplied by 125%, then adding the new charger. Utilities in the metro increasingly have smart meters that record this; ask yours for 12 months of interval data.

In our 100 amp service guide we worked a 2,000 square foot example: with an electric range, dryer and water heater plus central air it calculates at about 103 amps, and adding a charger takes it to about 115, or about 133 if the inspector counts the charger at 100%. The same house on gas appliances has plenty of room. The appliances decide it, not the square footage.

Pick the charger size before you pick the panel

Level 2 chargers are continuous loads, so the circuit has to be rated at 125% of the charger's output. A 48 amp charger needs a 60 amp circuit; a 24 amp charger needs a 30 amp circuit. Many hardwired chargers can be set to a lower output during installation, and the 2023 NEC lets the lower setting count in the load calculation when access to the setting is restricted.

For most commuters, a smaller setting costs almost nothing in practice. Tesla's published figures for a Model 3 or Y show 24 amps adding about 22 miles of range per hour. Eight hours overnight at that rate is roughly 175 miles, which covers most days in the Portland-Vancouver metro several times over.

Range per hour varies by vehicle; trucks and larger SUVs add fewer miles per kilowatt. The Department of Energy's rule of thumb for Level 2 is about 25 miles per hour of charging at around 7 kW.

Load management: charging without a panel upgrade

When the calculation does not fit, the code has an answer besides a bigger service. The 2023 NEC allows an energy management system to limit the charger so the service is never overloaded. When a system like that is used, the charger is counted at the maximum the system allows rather than its full rating (625.42(A)), and a whole-feeder system can be counted at its setpoint (220.70).

In plain terms, a monitor watches the house's total current and slows or pauses the charger when the dryer, oven and heat are all running, then lets it run again when they are not. Because EV charging mostly happens overnight, it usually loses little or no charging time.

Any device used this way has to be listed for the purpose and installed to its instructions, and the permit drawings or notes should say how the charger is limited. We confirm with the local inspector before choosing a device, because acceptance of the plug-in splitter type in particular varies.

When a panel upgrade is the better answer

Load management is a tool for fitting one more load onto a service that is close to full. It is not a substitute for capacity when the whole house is going electric. We recommend going to 200 amps when any of these are true.

• A heat pump with electric backup heat is being added now or soon. In the worked example, a heat pump alone pushes the house to about 125 amps before any charger.
• A second EV, an induction range, a hot tub or a shop subpanel is on the list for the next few years.
• The panel is Federal Pacific, Zinsco, a fuse box, or out of physical space, so it needs replacing anyway.
• The service mast, meter base or grounding needs work for other reasons, which makes the incremental cost of going to 200 amps small.

Permits for an EV charger in Portland and Vancouver

A Level 2 charger, hardwired or on a new 240 volt outlet, is a new branch circuit and needs an electrical permit and inspection on both sides of the river. In Oregon, a licensed contractor can often cover a wall-mounted charger with a state minor label, a $14 inspection label, instead of a full permit, but only for one new circuit of 40 amps or less at 240 volts, in a garage where the panel is within sight of the charger and not in a wet or damp location. Bigger chargers and panel or service changes need a regular permit.

In the City of Portland, a standalone circuit permit is $174 for the first circuit plus Oregon's 12% surcharge; if the charger is part of a panel upgrade, each added circuit is $21 on the same permit. In Washington, the permit comes from L&I or, inside Vancouver city limits, from the City of Vancouver. Our permit guide has the full fee tables.

What each route costs

These are our own numbers from paid invoices, August 2024 to August 2026, not market averages. The charger hardware can be yours or supplied by us.

Rebates can cover part of the charger job depending on your utility: Clark Public Utilities pays $500 for a connected Level 2 charger, and Pacific Power pays up to $1,500 for income-qualified customers. The details and eligibility are in our EV charger rebate guide.

What to send us for a quick answer

We can usually tell you which route fits from a few photos, before anyone visits.

1. A photo of the panel with the door open, and a close-up of the main breaker.
2. A photo of the meter and where the service enters the house.
3. A list of what is electric: heat, water heater, range, dryer, AC or heat pump, hot tub.
4. Where the car parks, and roughly how far that is from the panel.
5. Which charger you have or want, and what setting you would accept.

Sources

• Washington L&I: EVSE load calculation in the 2023 NEC
• Eaton: NEC 2023 home electrification changes, including 220.57
• Tesla Wall Connector: circuit sizes and charge rates
• Tesla Wall Connector power management
• US DOE Alternative Fuels Data Center: charging stations
• Emporia Pro EV charger
• RVE DCC-12 load controller specification sheet
• Oregon BCD minor label scope for electrical contractors
• Portland Electrical Permit Application