Why Your Existing Panel Probably Isn't Solar-Ready
Solar installers aren't electricians. They mount panels and run DC conduit to an inverter, but they can't upgrade your main service or add capacity to a full panel. Most residential panels installed before 2015 are already at or near capacity - every circuit slot is occupied, and the bus bars are sized for the home's original load.
Solar adds a new 240V circuit breaker (typically 20A to 40A depending on system size) that backfeeds power into your panel. The National Electrical Code requires specific calculations: the sum of your main breaker rating plus the solar breaker rating cannot exceed 120% of the panel's bus bar rating. A standard 200A panel with 200A main breaker has zero headroom for solar without a costly main breaker swap or a line-side tap. A 100A service is almost never compliant without a full service upgrade.
If your panel is full, corroded, an obsolete brand (Federal Pacific, Zinsco), or lacks physical space for a solar breaker, the solar company will walk away or subcontract the electrical work at a markup. Getting your panel solar-ready before you sign a solar contract saves time and often money.
What "Solar-Ready" Actually Means
A solar-ready electrical system has three things: adequate service capacity, a compliant main panel with room for the solar breaker, and a clear path from the rooftop inverter location to the panel. Start with service capacity. Most solar arrays for a typical single-family home require a 200A service minimum. If you're still on 100A or 150A service, you'll need the utility to upgrade the transformer and meter base, and a licensed electrician to install new service conductors, a new weatherhead or underground lateral, and a new main panel.
The panel itself must have at least one or two available breaker slots, depending on whether the inverter is single-phase or uses a dual-breaker configuration. The bus bars must be rated to handle the backfed current using the 120% rule. Many solar installers prefer a main lug panel with a separate disconnect, or a panel with a main breaker rated lower than the bus (a 200A-rated panel with a 175A or 150A main, leaving room for a 30A to 50A solar breaker).
Finally, you need a code-compliant wiring path. The inverter is usually mounted on an exterior wall near the panel or in the garage. If the panel is on the opposite side of the house or buried in a finished basement, the solar contractor faces expensive conduit runs through finished spaces. An electrician can relocate the panel closer to the planned inverter site, or install a solar-ready sub-panel adjacent to the inverter.
Service Upgrades: 100A to 200A and Why Timing Matters
Upgrading from 100A to 200A service is the single most common pre-solar electrical project. The work involves coordinating with the utility company for a meter pull, installing a new meter base and main panel, running new copper service conductors (typically 2/0 or larger aluminum), and updating the grounding electrode system to current NEC standards. The entire home is without power during the swap - usually four to eight hours if scheduled properly.
Timing matters because the utility has its own schedule. In South Florida, meter reconnection requests can take one to three weeks depending on the provider and season. If you wait until after signing a solar contract, the solar company's timeline is already locked in, and delays trigger rescheduling fees or lost incentive deadlines. Do the service upgrade first, on your own timeline.
While the panel is open, upgrade any aluminum branch wiring with failing connections, add AFCI/GFCI protection to bedrooms and wet areas, and install a whole-house surge protector - solar inverters are sensitive to voltage spikes. This is also the moment to add circuits for EV charging (a NEMA 14-50 outlet or hardwired EVSE on a dedicated 50A or 60A circuit) or a future hot tub. One electrical permit, one utility coordination, multiple upgrades.
Panel Replacement vs. Adding a Solar-Ready Sub-Panel
If your main panel is in good shape but simply full, you have two paths: replace the entire panel with a larger model, or add a solar-ready sub-panel fed from the main. Panel replacement makes sense if the existing panel is outdated, undersized, or in the wrong location. A new 200A, 40-space panel with combination AFCI/GFCI breakers and built-in surge protection future-proofs the home and simplifies the solar interconnection.
A sub-panel works when the main panel is newer, correctly sized, and code-compliant, but has no open slots. The electrician installs a large breaker (60A to 100A) in the main panel, runs feeder cable to a new sub-panel near the planned inverter location, and designates slots in the sub-panel for the solar backfeed and any other future loads (EV charger, pool equipment, workshop circuits). This approach costs less than a full main panel swap and keeps the solar wiring isolated from the home's existing circuits.
Either way, the work must be permitted and inspected. Unpermitted electrical modifications void homeowner's insurance and create liability if there's ever a fire or injury. Solar installers will not connect to unpermitted panels - they have their own licensing and insurance at stake. For a full list of electrical services including panel upgrades, visit our services page.
Grounding, Surge Protection, and Other Code Requirements
Solar inverters inject current onto the same conductors that power your home, which means lightning strikes and grid surges hit the inverter and the panel simultaneously. The NEC requires bonding the inverter chassis to the panel's grounding system and installing surge protective devices (SPDs) on both the AC and DC sides of the system. Many jurisdictions now mandate whole-house Type 2 SPDs in the main panel for any new solar installation.
The grounding electrode system must meet current code - two ground rods minimum, properly spaced, with a continuous copper grounding electrode conductor. Older homes often have a single ground rod or rely solely on a metal water pipe that has since been replaced with PVC. An electrician will verify and upgrade the grounding during the panel prep. This isn't cosmetic; improper grounding causes inverter shutdowns, nuisance trips, and potential shock hazards.
Some utilities and local inspectors also require a visible, lockable AC disconnect within sight of the meter, separate from the panel's main breaker. If your main panel is indoors or around a corner from the meter, budget for an outdoor disconnect enclosure. The solar installer will use this disconnect for lockout/tagout during maintenance, and the fire department will use it in an emergency.
How Much It Costs and What to Expect
A 100A-to-200A service upgrade with a new 200A main panel typically runs $3,000 to $6,000 in South Florida, depending on service conductor length, whether the service is overhead or underground, and how much interior rewiring is required. Adding a solar-ready sub-panel to an existing compliant service costs $1,500 to $3,000. If the utility needs to upgrade the transformer or install a new lateral, add their fees (sometimes waived, sometimes $500+).
Permits run $200 to $400. Inspection timelines vary by municipality - some inspect within three business days, others take two weeks. The electrician will schedule the utility meter pull after the rough-in inspection passes and reconnection after the final inspection. Total project duration is typically two to four weeks from permit application to final sign-off, assuming no utility delays.
Get the electrical work done before you sign a solar contract. The solar company will do a site audit and see a modern, code-compliant, solar-ready panel with documented permits. Their quote will be lower because they're not subcontracting electrical work, and their installation will go faster because they're not waiting on someone else's permit. You control the timeline and the quality of the prep work. For more solar and electrical insights, check out our blog.
DIY Checks You Can Do Before Calling an Electrician
Open your main panel cover (with the main breaker off if you're uncomfortable, though just looking is safe). Count the available breaker slots. Check the label inside the door for the panel's bus bar rating and main breaker size. If it's a 100A or 125A panel, you almost certainly need a service upgrade. If it's 200A but every slot is full and the main breaker is also 200A, you'll need a panel swap or sub-panel.
Look at the brand. Federal Pacific (FPE) panels with Stab-Lok breakers and Zinsco panels are fire hazards and not insurable - no solar company will touch them. If you see rust, water stains, burn marks, or a hot smell near any breaker, stop and call a licensed electrician immediately. Do not attempt any work inside the panel beyond visual inspection.
Check your main service conductors where they enter the weatherhead or run underground. If they're aluminum and smaller than a quarter-inch diameter, you're likely on 100A service. Measure the distance from your meter to where you plan to mount the solar inverter - longer than 50 feet starts adding cost for conduit and wire. These observations help you have an informed conversation when you request a quote.