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Drill Down:
Your Enigmatic Electrical Panel

Someone made the comment to me recently that he had room to add an electrical circuit for a water heater because there were a couple of circuit breaker spaces open in his electrical panel. That seems logical, but is it true? Read on to find out.

Electrical Panel Basics

Your home has a main electrical panel outside where the utility service is connected and, usually, one or more sub-panels inside that make it convenient turn the electricity on/off in various places. The main panel is typically

Electrical panels are both simple and mysterious. The simple part is how to turn a circuit off or back on by throwing a breaker switch when needed. But what goes on behind the cover is a mystery to most people. How much electrification you can do depends a lot on the situation with your electrical panel(s).

A Common Mistake

You may be tempted to add the numbers on the circuit breakers to see whether the sum is greater than the power coming into the panel. But that won't tell you whether it's overloaded either. This

"I've got a couple of breaker slots open. So, I can add another circuit."

The converse statement would be, "All of the breaker slots are full. So, we can't add another circuit."

Are either of these electrical panels is overloaded?
Electrical Panel 2.jpg

Most people would guess the panel with the cover removed and wiring exposed is overloaded. I find this photo to be unsettling at first glance because the wiring is crowded, the environment is a little creepy, and the photography is not professional. The other panel with the cover on looks clean and orderly although all breaker spaces have been used.

The truth is that it's not possible to tell whether either of these electrical panels is overloaded just by looking at photos. We can see that all of the circuit breaker slots have been used in each panel. But that doesn't tell us whether they are overloaded. All we can conclude is that it may be difficult to add another electrical circuit.

A Common Mistake

You may be tempted to add the numbers on the circuit breakers to see whether the sum is greater than the power coming into the panel. But that won't tell you whether it's overloaded either. This is because the number on the circuit breaker is how many amps (amperes) of electrical current will trip the breaker (i.e., trigger over-current protection). It says nothing about the load that's connected to each circuit or the panel as a whole.

Methods to Determine the Load

There are two ways to determine the load connected to an electrical panel. The first is to calculate it according to the National and California Electrical Codes. This involves walking around to read labels on various things and applying rules to estimate the load on each circuit, on each panel, and for the home as a whole. This is the main method your local building department recognizes when issuing electrical permits.

 

A second way to determine the electrical load is to rent some equipment and collect data for a month or longer. It's the only way to know for certain what the maximum electrical load is for a home. This method is used when there's reason to believe the real-world load is significantly lower than the calculated load. The data can be shared with the local building department to secure approval for an increase to the electrical load without expensive upgrades to the panel and/or utility service.

Be a Good Steward

Many electricians won't bother doing a load calculation—especially the ones who don't get permits for new circuits. They just look at the panel and make an educated guess as to whether there's enough juice to install another circuit. But one-too-many ad hoc additions can result in overloaded circuits and panels.

 

For a flat fee, G2e Advisors will ...

  • Calculate the electrical load of your home and how much room you have to grow

  • Determine whether your panel(s) and utility service need upgrades to support additional load

  • Help you plan for new circuits and upgrades, if needed

If you're serious about keeping your home safe, then be a good steward of your electrical system.

Woody

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