Your electrical panel has a total capacity, and your existing appliances use a portion of it. A load calculation adds up the demand from your current circuits and compares it against what the panel can handle. NEC Article 220 sets the standard method for doing this.
The result tells you whether there’s headroom for a new 40 or 50-amp EV charger circuit, a solar inverter, or a battery connection. A 200-amp panel doesn’t automatically mean you have room. One that already serves electric heat, an electric range, a dryer, and a heat pump may be close to its limit. A 100-amp panel often is.
A load calculation takes 15 to 30 minutes on a site visit. Some electricians skip it and recommend a panel upgrade by default when a customer asks about an EV charger. That’s worth pushing back on.
When you’re getting quotes
Before agreeing to a panel upgrade, ask the electrician to show you the load calculation. It should be an actual number against your panel’s capacity, not a guess. If they can’t produce one, get a second opinion. The calculation is what justifies the upgrade recommendation. Without it, you’re just taking their word for it.
Common questions
- Do I need a load calculation before adding an EV charger in North Carolina?
- You don't need one by law, but you should ask for one before agreeing to a panel upgrade. A load calculation determines whether your existing panel has room for an EV charger circuit. Many homes in Raleigh and Charlotte with 200-amp service have enough available capacity and don't need an upgrade — but some electricians recommend one by default without checking.
- How much does a load calculation cost in NC?
- Most licensed electricians in North Carolina perform a load calculation as part of a site assessment, which is typically free or included in the quote. If an electrician charges separately for it, that's unusual. It takes 15 to 30 minutes on-site and should produce a written result showing your panel's current load versus its rated capacity.
- Can a 100-amp panel support an EV charger in North Carolina?
- Sometimes. It depends on what's already running on the panel. A 100-amp panel in an older home with gas heat, a gas range, and few high-draw electric appliances may have enough headroom for a 32-amp EV charger circuit. One that already serves electric heat, a dryer, and air conditioning is likely at or near capacity. A load calculation tells you which situation you're in.