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Do I Need a New Electrical Panel When Going Solar?: 3 Reasons You Might

Updated: Apr 29

hand adjusting main service panel breaker

As you embark on the journey towards harnessing the power of solar energy for your home, you're likely filled with excitement about the prospect of freeing your home from reliance on the grid. However, amidst all the planning and preparation, one crucial question often arises: Do you need a new electrical panel when going solar? It's a question we encounter frequently, and today, we'll delve into three compelling reasons why a main service upgrade might be necessary.

Need a new electrical panel? Why you might...

Insufficient Capacity

Picture this scenario: you've decided to install solar panels on your home, eager to reduce your reliance on traditional grid electricity. However, upon closer inspection, you discover that your electrical panel is too small to accommodate the additional energy load from the solar system. Many older homes are equipped with 100 amp electrical panels, which may have been adequate in the past but are now inadequate, especially with the rise in solar and battery storage. With the integration of batteries and other modern energy technologies, an electrical panel upgrade becomes increasingly beneficial to ensure your system can handle the demands of solar energy production.

Age and Safety Concerns

Another significant reason for considering a main service upgrade is the age and condition of your current electrical panel. In particular, panels manufactured by Zinsco are prevalent in certain areas but are notorious for their safety hazards. Over time, Zinsco panels have been known to develop issues as indicated by burn marks on the busbar, which poses serious fire risks. While not all Zinsco panels are inherently dangerous, any signs of wear or damage warrant immediate attention and likely necessitate a panel replacement for the safety of your home and family.

Compliance Regulations and use of Modern Technology

To regulate the flow of solar and battery power into the main electrical panel, there are newer technologies available from Enphase, Tesla, and SolarEdge called the PCS (Power Control System) feature. While this feature can be helpful in specific scenarios, it's often not the ideal solution. It enables the restriction of the amount of electricity sent back to your main panel to comply with the “120% rule”. However, its effectiveness varies.

What is the 120% rule? Established by the National Electrical Code (NEC), this regulation serves to protect life and property from electrical hazards. At the heart of your home's electrical system lies the Main Service Panel (MSP), which receives power from your new solar energy system. MSPs are rated in amps, indicating their capacity to handle electrical currents. It's essential to ensure that the additional electricity generated by the solar system doesn't exceed the MSP's capacity, thus maintaining safety standards.

The "120% rule" mandates that solar PV systems should be connected to electrical panels whose capacity is up to 120% of the busbar's label rating. Adhering to this guideline ensures that the integration of solar energy poses no risk to the electrical infrastructure of the property.

For example, let's consider a scenario where a home with a 100 amp main panel requires a 4 kW solar system and two grid-tied batteries, totaling 60 amps of power to be fed into the main panel. According to the “120% rule” (100A panel x 1.2 - 100 A breaker size), this would allow only 20 amps of power on a 100 amp service. While the PCS could limit the system to back feed only 20 amps, this might significantly reduce the amount of savings on the customer's electric bill.

This highlights the importance of properly sizing the main panel when designing a solar system. Unfortunately, many companies overlook this crucial step, potentially leading to suboptimal performance and savings for the customer.


In conclusion, a main service upgrade is not just a technicality; it's a critical step in ensuring the safety, efficiency, and compliance of your solar energy system. By addressing issues related to panel size, age, and compatibility with modern technology, you can maximize the benefits of solar energy while safeguarding your home and investment for years to come. Before embarking on your solar journey, consult with knowledgeable professionals to assess whether a main service upgrade is necessary for your specific situation. Your future with solar energy starts with a solid foundation – make sure your electrical panel is up to the task.

If you would like a free consultation to assess your solar and main service panel needs contact us here.


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