If you’re considering going solar, one of the most important things to look at—before you even think about the panels or the battery—is your electrical panel. Your panel is the heart of your home’s electrical system, and it plays a major role in determining whether your house is ready to safely handle the power that a solar system will generate.
At Supreme Solar and Electric, we’ve helped hundreds of homeowners in Fresno and the Coachella Valley get their homes solar-ready. In many cases, that process starts with evaluating the panel.
So how do you know if your electrical panel is ready for solar?
This guide will break it down in simple terms, explain what we look for, and walk you through the latest technology—like power control systems—that can make solar possible, even for homes with older panels.
What Is an Electrical Panel?
Your electrical panel—also known as a breaker box or load center—is the metal box (usually outside on the side of your house or inside the garage) that contains all the breakers and safety switches for your home’s electrical system.
It distributes power from your utility to the various circuits in your home, and it’s where we will connect your solar system so that it can feed energy back into your home.
When we evaluate your electrical panel for solar, there are two critical components we look at:
- Main Breaker Size
- Bus Bar Rating
1. Main Breaker Size
The main breaker is the large switch at the top of your panel that controls the power supply to the entire house. It acts as your main line of defense—shutting off all power in the event of a major fault or issue.
Most residential homes have a main breaker rated at either:
- 100 amps
- 125 amps
- 200 amps
This number tells us the maximum amount of electrical current your home can safely handle at any one time.
When we design a solar system, especially one paired with a battery, we have to consider how much energy the system will produce and send into the panel. If your main breaker is too small, it could be a problem—and it may require an upgrade.
2. Bus Bar Rating
The second piece we check is the bus bar rating. The bus bar is the internal backbone of the panel—it’s the metal strip that distributes power from the main breaker to the individual branch circuit breakers.
Just like your main breaker, your bus bar has a maximum current rating. This is often printed inside the panel cover, and it’s essential to know because the National Electrical Code (NEC) limits how much current can flow through the panel based on that rating.
Here’s the issue: when you add solar, you’re not just consuming energy—you’re also generating it. That extra energy is called backfeed, and it flows back into your electrical panel. If you send too much energy into a panel with a low bus bar rating, it becomes a fire risk.
That’s why we’re required to ensure the total amperage (main breaker + solar backfeed) does not exceed 120% of the panel’s bus bar rating. This is called the 120% Rule.
What That Looks Like:
Let’s say you have a 100-amp main breaker and a 100-amp bus bar:
- 120% of 100 amps = 120 amps allowed
- If your main breaker is 100 amps, you can only backfeed 20 amps from solar
That limits how many panels you can install without upgrading your panel or using more advanced technology, like a power control system (we’ll explain that soon).
What Size Solar System Can My Panel Handle?
While the exact number of panels depends on the wattage of the panels and your inverter, here are some general rules of thumb:
For a 100 or 125 Amp Panel:
- Typically supports 10 to 16 solar panels (depending on wattage)
- With today’s higher-output panels (430–460 watts), that’s about 7 to 8 kW of solar
- You’ll need to limit system size unless you upgrade your panel or use a power control system
For a 200 Amp Panel:
- Can usually support 25 to 30 panels
- With modern panels, that’s about 12 to 14 kW of solar
- Can easily support a solar + battery system
Typical Home Sizes and Panel Ratings:
- 1,400 sq ft or less: Often has a 100 or 125 amp panel
- 1,400+ sq ft: Usually equipped with a 200 amp panel
That said, even smaller homes are installing bigger systems today—especially if they have EV chargers, pool pumps, or plan to electrify appliances. So understanding your panel’s limitations is key.
What If My Panel Can’t Handle the Solar System I Need?
If your panel doesn’t have enough capacity for the solar system you want, you’ve got a few options:
Option 1: Main Panel Upgrade (MPU)
This involves replacing your entire panel with a new one—usually a 200 amp panel with a higher bus bar rating.
Pros:
- Allows for larger solar systems
- Future-proofs your home for EVs, electric appliances, etc.
- Clean install with updated breakers and wiring
Cons:
- Increases the cost of your solar project
- May require utility coordination and permit approval
- Could require upgrading the service wire from the utility pole to your home
This is often the best long-term option, especially if your existing panel is outdated or maxed out.
Option 2: Load Side Tap or Line Side Tap
This is a method of connecting the solar system directly into the main service wire, bypassing the limitations of the breaker slots.
Pros:
- Avoids a full panel upgrade
- Can be a workaround in some jurisdictions
Cons:
- Not always approved by local utilities
- More complex installation
Option 3: Power Control System (PCS)
This is the newest and most advanced solution. A Power Control System is a smart inverter or energy management device that can dynamically throttle your solar output based on how much power your home is using in real-time.
Think of it as the brain of your system—it protects your panel by adjusting output before it overloads.
Here’s how it works:
- The PCS constantly monitors your home’s electrical usage
- If your usage is low and solar production is high, it throttles down the solar output
- This keeps your total current flow under the panel’s bus bar rating
Why It’s a Game-Changer:
- Allows you to install a larger solar system without upgrading your panel
- Approved under the latest National Electrical Code (NEC)
- Often built into smart hybrid inverters used with batteries
If you have a 100 or 125 amp panel and want a full solar + battery system, a PCS might be the perfect solution.
When Should I Upgrade My Panel?
Here are a few signs it’s time for a panel upgrade before going solar:
- Your panel is over 25 years old
- You have less than 200 amps and want a large system with a battery
- You plan to install an EV charger, heat pump, or electric range soon
- Your current panel is a brand known for safety issues (like Zinsco or Federal Pacific)
Remember, the goal isn’t just to “pass inspection”—it’s to make sure your system is safe, reliable, and scalable for your future energy needs.
Can I Still Get Solar Without Upgrading My Panel?
Yes! Thanks to higher efficiency panels, smart inverter technology, and power control systems, many homeowners can still go solar even with older or smaller panels.
That’s where working with a qualified contractor like Supreme Solar and Electric makes all the difference. We evaluate your electrical panel during our initial site survey and recommend the best path forward—whether that’s a panel upgrade, a PCS solution, or a load-side tap.
Final Thoughts: Start With the Panel
Your solar journey doesn’t start with panels or batteries—it starts with the electrical panel. This often-overlooked component determines how big your system can be, how safely it can operate, and how much you can grow in the future.
At Supreme Solar and Electric, we take the time to inspect your panel, check your breaker size, and confirm your bus bar rating to make sure you’re set up for success.
Whether you need an upgrade or can go solar with your existing setup, we’ll help you make the right call.
Ready to Find Out If Your Panel Is Solar-Ready?
Let’s take a look. Contact Supreme Solar and Electric for a free site evaluation. We’ll inspect your panel, show you your options, and help you build a solar solution that’s safe, smart, and built to last.
