Will You Need a Panel Upgrade to Go Solar? Here’s How to Tell

When you're planning a solar project, one of the most common questions that comes up is whether your existing electrical panel can handle the new system, or if it’ll need an upgrade.

The short answer? It depends. Here’s what you need to know.

Why Your Panel Matters

When solar is added to your home, a new circuit gets connected to your main electrical panel. To stay code-compliant, we have to follow something called the 120% Rule from the National Electric Code. In plain terms, it limits how much solar can be added based on your panel’s size.

The Quick Rule of Thumb

If your panel is already 200 amps or more, no upgrade is likely needed.If your panel is under 200 amps, we’ll need to look closer. Whether or not it needs upgrading depends on the size of your solar system and any future plans you have (like adding an EV charger or heat pump).

4 Ways to Avoid a Full Panel Upgrade

Not every situation requires a panel upgrade for solar. Here are the most common workarounds, and when they make sense:

1. Derating the Main Breaker

Most common and cost-effective: Instead of upgrading your whole panel, we may be able to just swap out your main breaker for a slightly smaller one. For example, if you have a 200A panel with a 200A main breaker, we might install a 175A breaker instead, opening up space to safely add your solar circuit.

2. Generation Meter Adapter (SCE only)

Territory-specific, longer timeline: If you're in SCE territory (not LADWP, BWP, GWP, or PWP), you may be eligible for a GMA. It’s a device that allows your solar system to connect at the meter, bypassing the need to touch the main panel at all.

SCE charges a $500 service fee, and the processing time can add a few months to your project. This option works for homes up to 200A.

Heads-up: If you know you’ll eventually upgrade your panel for an EV or HVAC system, it’s usually better to do it now rather than delay.

3. Line Side Tap

Rare and jurisdiction-dependent: This method connects solar before the main breaker, directly into the utility feed. Some cities allow it, most don’t. It’s an option, but not one we recommend unless it’s the only path forward.

4. Downsizing Your Solar System

Least recommended: Reducing your system size just to avoid a panel upgrade might save money up front, but it can limit your long-term savings and your ability to cover future electric loads. We only consider this if absolutely necessary and with your goals in mind.

Do you need a panel upgrade for solar?

If none of the workarounds apply, or if you’ve got an older 100A panel and big plans for electric appliances, it might be time for a full upgrade. The cost varies based on your utility’s requirements, the location of your current panel, and whether there are any code issues (like the panel facing the street or being too close to a gas line).

As part of your project, OneSun handles the utility coordination, including something called a meter spot request. This determines where the upgraded panel can go and confirms the scope of work.

Panel upgrades are sometimes necessary, but not always. And when they are, we’ll walk you through the options clearly.

If you're thinking about solar and wondering what your electrical setup means for the project, reach out to us for a free evaluation—no pressure, just facts.