Do You Need a Panel Upgrade for Solar in Phoenix?

Whether you need a panel upgrade for solar in Phoenix comes down to one question: can your existing panel safely accept a second source of power? Your panel was built to take power from one direction, the utility, and hand it out to your circuits. Solar adds a second source feeding back into the same equipment. Some panels handle that with room to spare. Many older and builder-grade panels don't, and that's when the solar installer calls an electrician.

Why solar can require a panel upgrade

Inside your panel, the breakers clip onto metal bars called the busbar. The busbar has a rating, and so does the main breaker that protects it. When solar backfeeds through a breaker in the same panel, the busbar can end up carrying current from both the utility and the solar at the same time. The electrical code limits how much backfed solar a given busbar may accept. In a common setup, the main breaker plus the solar breaker can't exceed 120 percent of the busbar rating, and the solar breaker has to sit at the opposite end of the bus from the main.

In plain terms: a panel whose main breaker is the same size as its busbar has limited room for solar. A larger system may simply not fit on that panel as it is. That's the most common reason a Phoenix solar job turns into a panel job.

Options besides replacing the panel

A new panel isn't the only answer, and a good electrician will walk you through the choices before recommending one. Which of these works depends on your equipment, your utility and your plans.

• Size the system to fit the panel. Sometimes a slightly smaller array fits within the panel's limits with no electrical changes. Worth asking about if the numbers are close.
• Main breaker derate. Swapping the main for a smaller breaker frees up room for solar. It only works if a load calculation shows the house can live on the smaller main, which is harder in Phoenix where the AC is a big, long-running load.
• Supply-side connection. Solar can connect ahead of the main breaker instead of through the panel bus. Whether that's allowed, and how, depends on your meter equipment and the utility's rules, so it has to be confirmed before anyone plans on it.
• Panel or service upgrade. A new panel with a larger busbar, or a new meter-main combination, gives the solar a proper place to land and usually adds space for future circuits too.

Older Tempe and Phoenix homes: where it usually comes up

A lot of the houses in Tempe, central Phoenix and west Mesa were built in the 1960s and 70s. Many still have their original panel, and some have a small service by today's standards. Add a roof full of panels, an EV and a larger heat pump, and the original equipment runs out of room fast. Newer homes in Chandler and Gilbert usually have larger service, but builder-grade panels often left little space for anything beyond day-one circuits.

Heat matters too. Panels on west- and south-facing walls in the Valley spend the summer in direct sun. Before tying a new source into an old panel, it's worth looking for discolored breakers, brittle insulation and corroded lugs. If the panel is already tired, solar is a good time to replace it, not a reason to put it off. Signs your panel needs an upgrade →

SRP, APS and the approval process

Tempe and most of the East Valley are served by SRP. Much of Phoenix and the West Valley is APS. Both utilities require an interconnection application and their own approval before a solar system is turned on, and both have rules for the meter and service equipment. If the panel or meter is being replaced as part of the solar job, the city inspects that work, and the utility handles the disconnect, reconnect and meter. Getting the sequence right keeps you from paying for two outages or waiting weeks between steps. How SRP and APS service upgrades differ →

The U.S. Department of Energy's homeowner's guide to going solar is a good neutral overview of the rest of the decision, including financing and choosing an installer.

Solar, batteries and EV chargers: plan them together

If a battery or an EV charger is anywhere in your plans, say so before the panel work is designed. A battery often adds its own equipment near the panel, and an EV charger is a large continuous load that belongs in the same load calculation. Planning once costs less than opening the wall twice. What to know before adding an EV charger →

Questions to ask your solar installer

• Did you look at my panel's busbar and main breaker rating, and does the system fit as designed?
• If the panel has to change, is that in the contract, or is it an extra I'll pay someone else for?
• Who pulls the electrical permit for the panel work, and who schedules the utility?
• Is the electrician doing the panel work licensed in Arizona? You can check any contractor on the Arizona ROC contractor search.
• Will the new setup leave space for an EV charger or battery later?

How much does a panel upgrade for solar cost?

It depends on whether you need a new panel only, a new meter-main, or a full service upgrade, and on what SRP or APS requires at your address. We've laid out what drives the price here: What a panel upgrade costs in Phoenix →

Getting solar and need your panel checked?

Send us a photo of your panel with the door open, including the labels, plus the size of the solar system you've been quoted. We'll tell you whether the panel can take it, what your options are, and give you a free written estimate if work is needed. B and D Electric LLC is licensed and bonded, Arizona ROC 361086, and our two owners have more than 40 years of combined experience. See our panel and service upgrades. Call or text (480) 828-1181, or request an estimate.