Subpanel vs Main Panel: A Simple Explanation of a Complex Topic

If questions about the main panel rarely come up, not everyone knows that a modern home often has another hero — the subpanel. Why is it there? In this article, Freon Service will explain in detail. By the end, you won’t just understand that if one is the “mission control center,” the other is the “local manager.” You’ll also discover the fascinating world of organizing a safe, stable, and properly calculated electrical system.

Separation of Ground and Neutral: Difference Between Main Panel and Subpanel

When managing the electrical system of a large home, everything needs to be perfectly organized — starting with the main hero of our article, because this is where “power” flows out to every corner of the house.

Inside this box are two elements. Think of them like two employees sharing an office: neutral and ground.

• They work together, but sit at separate desks.
• Their actions serve the same overall purpose, but they shouldn’t perform each other’s duties.

Looking at the subpanel vs main panel situation, we see that in the main panel, neutral and ground are connected. Why is this done intentionally, and only once for the entire house?

• Because this is the starting point, the “zero level,” from which energy enters the home.
• Here there must be a single, clear path that returns current to the ground in case of a fault.

It’s like the only emergency exit in a large building — it must be one, clear, and controlled.

The difference between main panel and subpanel is that the latter “separates to prevent chaos.” Why?

Imagine letting these two employees sit side by side again. Here’s what could happen:

• Situation 1: Lost current

If neutral and ground are connected in a subpanel, part of the current starts flowing through the grounding wires, pipes, and equipment enclosures.

It’s like the employees running not through the hallways, but through the ventilation system:

– Fast? Maybe.

– Safe? NEVER.

• Situation 2: A “live” frame in the workshop

You turn on a machine, and suddenly the metal frame receives stray current through the ground — giving a slight “tingle.”

This isn’t just unpleasant — it can be dangerous.

The main point is: in your estate, no matter how big, there can only be a single control point where neutral and ground are connected.

Backfeed as an Indicator of the Difference Between Main Panel and Subpanel

Imagine the current suddenly finding a new path it wasn’t supposed to see:

• Neutral and ground connected in a subpanel.
• A loosely secured wire.
• An extra grounding point that “dad installed back in 1978”.

Then the current starts returning to the source not through the neutral, but through anything it can touch. This is backfeed.

In the context of main panel and subpanel, backfeed happens when part of the current that should flow along its clean, predictable path (the neutral) suddenly starts traveling throughout the house:

• You turn on a band saw or air compressor — and feel a slight “tingle” on the frame.
• Electric shocks can appear on a faucet, radiator, or pipe.

This isn’t static electricity. It’s a stray current that came back through the ground. And it’s dangerous.

The technicians at Freon Service don’t just install a subpanel — they make sure that the combination of your “existing electrical system” + the “new upgrade” doesn’t create the hazard of stray current.

Difference Between Sub Panel and Main Panel — How to Deliver Power from One to the Other

To do this correctly, our technicians use a four-wire feeder. It includes:

• Two hot wires. Essentially, these are the “muscles” of the system, carrying 240 V for heavy appliances and 120 V for regular ones.
• One neutral conductor. This is the working path for returning current.
• One separate grounding conductor. It sits quietly, does nothing, and only activates in an emergency, safely directing dangerous current to the ground.

If we put the main panel and subpanel into a visual analogy, you can picture it like trucks on a road:

• Hot wires — two big rigs delivering energy to the subpanel.
• Neutral — the worker collecting empty containers and bringing them back.
• Ground — the tow truck that only activates in case of an emergency.

If you only had three wires instead of four, the tow truck would have to drive on the same road as the regular trucks. And that’s a recipe for disaster.

Thanks to having two separate return paths, this feeder prevents the creation of backfeed.

Main Panel and Subpanel — Do You Need Both?

Answering this question requires a careful load calculation. To avoid constant breaker trips, overloads, and risks, it’s important to understand how much energy your appliances will “pull.” To do this:

• List all appliances/circuits that will be powered by the subpanel:
  • lighting,
  • outlets,
  • stationary tools,
  • washer,
  • dryer,
  • EV charger,
  • HVAC, etc.
• Determine their power (in watts) or current (in amps).
• Sum up the continuous and temporary loads:
  • Continuous loads are, for example, the refrigerator and lighting.
  • Temporary loads are drills in the workshop, welders, stoves — basically, anything that’s not on all the time.
• Apply demand factors.
• Convert the power to amps for the chosen voltage.
• Keep in mind that a panel shouldn’t operate at 100% capacity continuously. Leave a buffer — 80% is sufficient.

So, this isn’t just about the winner in the subpanel vs main panel matchup. It’s about understanding the total demand considering the existing loads in your home. If it exceeds the main service’s capacity, an upgrade may be required (for example, to 200 A).

We always recommend planning a buffer: it’s better to have a slightly larger panel than one that’s maxed out.

Load calculations aren’t always simple. Applying demand factors and accounting for complex loads can take significant time. The best approach is to hand this task to the technicians at Freon Service. We will promptly:

• perform the calculation according to NEC/CEC,
• advise if a service upgrade is needed,
• select appropriate wire sizes and breakers,
• handle the permit.

But the benefits don’t stop there: if you want everything done by the book, considering the difference between sub panel and main panel, and with no surprises, we’ve got you covered. We don’t just “install a panel” — we make sure every wire and every label inside is logical, neat, and clear to any inspector. No chaos, no unnecessary discussion, no delays “for later.”