Why Playing It Safe Isn’t Optional—It’s the Law (And Smart Business)

At Santiban Services Group, we believe that doing it right means doing it safe. That’s why every single EV charger or energy system we install begins with one critical task: a full electrical load calculation. This isn’t optional—it’s required by the National Electrical Code (NEC) and backed by manufacturer safety guidelines. And yet, so many contractors skip it.
Spoiler alert: skipping a load calc could leave you with a burnt panel, denied insurance claims, or worse—a fire you didn’t see coming.

What Is a Load Calculation—and Why Should You Care?

A load calculation measures how much power your home’s electrical panel is already using, and how much extra it can safely handle. When adding EV chargers, battery storage systems, or even solar inverters, the new load must be calculated against your existing usage.
Most residential main breakers are not rated for 100% continuous load. Instead, the NEC and breaker manufacturers typically infer an 80% threshold for continuous usage—meaning your panel should not be routinely loaded beyond 80% of its main breaker rating.

NEC Code Breakdown:

• NEC 210.19(A)(1)(a): Continuous loads must be calculated at 125% of the actual load.
• NEC 210.20(A): Overcurrent protection devices (like breakers) must be properly rated to handle the load.
• NEC Article 220: Gives specific calculation methods for total load capacity.

• NEC 110.3(B): Equipment must be installed per manufacturer instructions—which nearly all state that breakers not rated for continuous 100% loading must follow the 80% rule.

UL and Siemens, Eaton, and Square D manufacturers all recommend not exceeding 80% of a breaker’s rated capacity unless the breaker is specifically listed for 100% continuous operation—which most residential breakers are not.

What Happens If You Ignore the 80% Rule?

Let’s say you have a 150A main panel. Using the 80% rule, you should not exceed 120A continuous load. But after HVAC, lighting, refrigerator, and now a 48A EV charger—you’re over. That means:

  • Increased fire risk
  • Tripped breakers and voltage drops
  •  EV charger failure or premature aging
  • Code violation = permit rejection = fines
  • Insurance claim denial if damage occurs