What is a Main Electrical Panel and Why Does It Matter?

Updated: Jun 16, 2025

As solar energy becomes an increasingly popular option for homeowners and businesses alike, many people are eager to make the switch to cleaner, more sustainable power. An often overlooked component of solar installations is the condition of your home’s electrical system, especially the main electrical panel. Suppose your existing electrical panel can’t handle the additional load generated by a solar system. In that case, you may need a main panel upgrade (MPU) before proceeding with installation in  your Arizona Home. 

At Solar Topps, we ensure your home’s electrical system is ready for a new solar installation. In this article, we’ll explore why a main panel upgrade might be needed and how Solar Topps can guide you.

How Your Main Electrical Panel Supports Solar

Your home’s main electrical panel, also called a breaker box or load center, distributes electricity throughout your home. It directs electrical current from the utility grid or your solar system to power your appliances, lighting, and other devices. Upgrade the panel if it’s outdated or too small for your solar installation to maintain safety and functionality.

The electrical panel divides into individual circuits, and breakers protect each one. Each breaker handles a specific number of amps. If a circuit overloads, the breaker trips and shuts off power to prevent fires or electrical hazards.

When Is a Main Panel Upgrade Necessary for Solar?

A main panel upgrade is often required when your existing panel is outdated, lacks sufficient capacity, or is not compliant with modern electrical codes. During the initial site assessment, a Solar Topps technician will inspect your electrical panel and determine if an MPU is needed. Here are some common reasons why you might need an upgrade:

• Insufficient Amps: If your electrical panel is below 200 amps, it might not handle the load from your solar system. Homes with 100 or 125 amp panels may need an upgrade, especially if the system exceeds 7.5 kW.
• Space Constraints: Sometimes, the existing electrical panel doesn’t have enough room to accommodate the additional breaker for the solar system. If no space is available, an MPU is required to make room for the new system.
• Outdated Panels: Sometimes, the existing panel might be an outdated model no longer approved by local utilities or building codes. This is especially common in homes built decades ago.

The 120% Rule and Solar Panel Sizing

Your electrical panel limits the size of your solar system. The 120% Rule ensures the combined load from your utility grid and solar system stays within 120% of the panel’s rated capacity. For example, if you have a 200-amp panel, your solar system’s total load must stay below 240 amps.

This rule protects your electrical system from overloading and reduces the risk of safety issues. Upgrading your electrical panel allows you to install a bigger solar system. This keeps your home’s wiring safe and sound.

Main Panel Upgrades: Cost and Time Considerations

If you need an MPU, consider the added cost and time involved. On average, an MPU can cost between $3,000 and $5,000 depending on the complexity of the installation. Though this may seem costly, it’s a crucial investment to ensure your solar system runs safely and efficiently. The good news is that MPU costs often qualify for the Federal Solar Investment Tax Credit (ITC). This helps lower the cost.

In addition to cost, a main panel upgrade can add time to your solar installation. Securing permits may take longer, and you may need to order additional components. Supply chain disruptions have also affected the availability of electrical panels, which can further delay installation. However, at Solar Topps in Phoenix, AZ, we plan ahead to minimize delays and keep your project on track.

Why Consider a Main Panel Upgrade?

While an MPU might seem like an inconvenience, it offers several long-term benefits, especially for homeowners looking to future-proof their energy systems:

• Increased Capacity for Future Upgrades: A larger main panel is essential for handling higher electrical loads from solar panels, EV chargers, or additional circuits.
• Enhanced Safety: Upgrading your panel ensures your electrical system meets modern safety standards, reducing fire or system failure risks.
• Optimized Energy Independence: A correctly sized electrical panel boosts your solar system’s efficiency, enhancing energy independence.

How to Determine If You Need an MPU

Before committing to a solar installation, assess whether your home needs an MPU. Solar Topps thoroughly evaluates your home’s electrical infrastructure through the following steps:

1. Virtual or On-Site Assessment: Solar Topps conducts virtual and in-person assessments to evaluate your main panel’s capacity. We review the panel’s amp rating and available space to quickly determine if an upgrade is necessary.
2. Compliance Check: Our technicians check your electrical panel to ensure it meets all local building codes and utility requirements.
3. Upgrade Planning: Solar Topps provides a clear estimate and timeline for MPU needs, ensuring transparency and minimizing project disruption.

Trust Solar Topps for Seamless Solar Installations

At Solar Topps, we deliver high-quality solar solutions built to last. Our experts guide you through the installation process, including any necessary electrical panel upgrades, to ensure your system fits your unique home.

If you’re ready to go solar, contact Solar Topps today. Schedule a consultation and let us help make your home solar-ready.

Main Panel Upgrade- Frequently Asked Questions (FAQ)

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What is a main electrical panel and what does it do?

A main electrical panel, sometimes called a breaker box or load center, is the central hub that distributes electricity throughout your home. It receives power from the utility grid or your solar system and routes it to your appliances and devices. The panel contains circuits and breakers that help prevent overloads and electrical hazards.

When do I need to upgrade my main electrical panel for solar?

Upgrade your main panel if it is outdated, has insufficient amp capacity (typically below 200 amps), lacks space for additional breakers, or fails to meet modern electrical codes. Solar Topps technicians will evaluate your panel and determine if an upgrade is necessary during your site evaluation.

What is the 120% Rule in relation to solar panel installations?

The 120% Rule states that the combined load from your utility grid and solar system cannot exceed 120% of your panel’s rated capacity. For example, a 200-amp panel should not have a total load over 240 amps. This ensures your electrical system stays safe and avoids overloading.

How much does a main panel upgrade typically cost and how long does it take?

A main panel upgrade generally costs between $3,000 and $5,000, depending on the installation’s complexity. The process can also add time to your solar installation due to permits, supply chain issues, and ordering extra components. Solar Topps works to minimize these delays.

What are the benefits of upgrading my main electrical panel?

Upgrading your main panel increases the capacity for future electrical upgrades, such as adding solar panels or EV chargers. It also enhances the safety of your home’s electrical system and allows for greater energy independence by optimizing your solar system’s performance.

Do incentives reduce the cost of a main panel upgrade?

Yes, the cost of a main panel upgrade often qualifies for the Federal Solar Investment Tax Credit (ITC), which can help reduce your out-of-pocket expense for upgrading your electrical panel during a solar installation.