Do You Need an Electrical Panel Upgrade Before Solar?
A solar array connects to the house at the main electrical panel, through a backfeed breaker, and the panel has to have the physical space and the rating to take it. On the 1960s and 1970s block homes that fill Pinellas County and west Hillsborough, it often does not: a 100-amp service, a Federal Pacific or Zinsco panel that should be replaced regardless of solar, or a 200-amp panel already full of breakers for a pool, a second air handler, and an EV charger. Fused Solar and Roofing checks the panel at the site survey, does the electrical work under its own license, and shows it as its own line on the proposal. Fused Solar and Roofing is a licensed roofing (CCC1331058), electrical (EC13014750), and building contractor (CBC1252064), all three in-house.
1. Why the panel matters
The National Electrical Code limits how much power can be fed back into a panel from solar based on the panel's bus rating and its main breaker, under what is usually called the 120 percent rule. On a 200-amp panel with a 200-amp main, that allows a solar backfeed breaker of up to 40 amps, which covers most residential systems. On a 100-amp panel the allowance is half that, which fits only a small array, and on a panel with no open breaker slots there is nowhere to land the backfeed at all. The panel sets the ceiling on the system before the roof does.
🔑 Key Takeaway: The panel's rating and its spare space decide how much solar can connect. On older homes it is often the first thing that has to change.
The utility has a say as well. Each Tampa Bay utility reviews the interconnection against the service size and the inverter rating, and a panel that cannot take the backfeed cleanly is a system the utility will not approve.
2. The 100-amp service
Homes built before the mid-1970s in St. Petersburg, Largo, Pinellas Park, Seminole, Town 'n' Country, Temple Terrace, and the older parts of Tampa commonly have 100-amp service. A 100-amp panel can take a small solar backfeed, but a home that has added central air, a pool pump, and a modern kitchen is usually at the limit of 100 amps already, and the right answer is a service upgrade to 200 amps before the solar. That is a new panel, a new meter base in most cases, and coordination with the utility to upgrade the service drop, done under Fused's electrical license as its own permit.
3. Federal Pacific, Zinsco, and other panels that should go anyway
Federal Pacific Stab-Lok and Zinsco panels, installed through the 1980s, have documented breaker failure problems and most electricians recommend replacing them regardless of solar; many insurers ask about them on a four-point inspection. Fused will not connect a solar backfeed to one. If the survey finds either, the proposal shows a panel replacement as its own line, and the homeowner gets a safer panel and a solar-ready one in the same job.
💡 Pro Tip: Open your panel door and read the label. If it says Federal Pacific, FPE, Stab-Lok, or Zinsco, plan on replacing it with or without solar, and tell your insurer's inspector it has been done.
4. The full 200-amp panel
A newer home with 200-amp service can still have no room. Pool equipment, a second air conditioner, an electric vehicle charger, a hot tub, and a workshop circuit fill a panel fast, and the backfeed breaker needs two slots and the headroom under the 120 percent rule. The options, from least to most expensive: a load-side tap or a supply-side connection that lands the solar without using breaker slots, where the code and the utility allow it; a subpanel to move circuits out of the main; or a new, larger panel. Fused picks the one that fits the house and the planned system and prices it as its own line.
5. Smart panels and batteries
A home adding a battery with its solar, or planning an EV charger and a battery, has a reason to look at a smart panel such as SPAN, which Fused installs. A smart panel manages which circuits run on battery during an outage and sheds loads to stay within the service rating, which can avoid a service upgrade that would otherwise be needed for the EV charger. It costs more than a conventional panel and is worth it on homes with a battery and growing electrical load; on a simple solar-only install, a conventional 200-amp panel is the right answer.
⚠️ Warning: A solar quote that does not name your panel's brand, rating, and spare capacity has not looked at it. On a home over forty years old that is the item most likely to appear after the deposit, and it can be several thousand dollars.
6. How Fused handles it
The surveyor photographs the panel inside and out at the site visit, reads the rating and the brand, and counts the open slots. The proposal then either says the panel is fine, or shows the electrical work as its own line: service upgrade, panel replacement, subpanel, or supply-side connection, with the reason. Fused Solar and Roofing is a licensed roofing (CCC1331058), electrical (EC13014750), and building contractor (CBC1252064), all three in-house. The electrical permit for the panel work is pulled under Fused's license alongside the solar permit, and the utility is coordinated for any service change. The homeowner sees the price before signing, not after.
If your roof ever needs replacing with solar on it, who is allowed to remove and reinstall the panels, and why, is covered in our guide at https://fusedsolarandroofing.com/post/who-can-remove-reinstall-solar-florida
7. What it costs and how it is financed
Panel work is priced by what the house needs, so Fused quotes it after the survey rather than from a menu. A straightforward 200-amp panel replacement is the common case; a full service upgrade with a new meter base and utility coordination is more; a smart panel is more again. It is financed with the solar through Climate First Bank as part of the project, so the homeowner is not paying for the electrical separately, and it appears as its own line so the homeowner can see it.
8. Why have the solar company do the panel
Because the panel and the solar are one electrical system and one inspection, and a homeowner who hires an electrician for the panel and a solar company for the array has two contractors arguing over the backfeed breaker. Fused holds the electrical license, does panel upgrades as a standalone service as well as with solar, and has worked on the 1960s and 1970s panels of Pinellas and west Hillsborough since 2007. The panel is not an obstacle to solar; it is the first line on the proposal.
🔑 Key Takeaway: 100 amps, Federal Pacific or Zinsco, or a full panel means electrical work before solar. Have it found at the survey, priced as its own line, and done by the company doing the solar.
Not sure what panel you have? Request a free site survey and solar quote at https://fusedsolarandroofing.com/solar-installation
Frequently Asked Questions
Can I install solar on a 100-amp electrical panel?
A small system, sometimes. Most Tampa Bay homes with 100-amp service are already near the limit, and the right answer is usually a 200-amp service upgrade before the solar, done under Fused's electrical license as its own line.
Why won't Fused connect solar to a Federal Pacific or Zinsco panel?
Both have documented breaker failure problems and most electricians recommend replacing them regardless of solar. Fused replaces the panel and connects the solar to the new one.
My 200-amp panel is full. Do I need a new one for solar?
Not always. A load-side tap or supply-side connection, or a subpanel, may land the solar without a new panel. Fused chooses the option that fits the house and prices it as its own line.
How does Fused know if my panel needs an upgrade?
The surveyor photographs the panel inside and out at the site visit, reads the rating and brand, and counts open slots. The proposal states the result and any electrical work before you sign.
Should I get a smart panel with solar?
If you are adding a battery or planning an EV charger, a smart panel like SPAN can manage loads and avoid a service upgrade. For solar alone, a conventional 200-amp panel is the right answer.
Can the electrical panel work be financed with the solar?
Yes, through Climate First Bank as part of the project, shown as its own line on the proposal.
Fused Solar and Roofing has installed solar across Hillsborough, Pinellas, Pasco, and Manatee counties since 2007, with the roof and the solar handled by its own licensed in-house crews. Request a free solar quote at https://fusedsolarandroofing.com/solar-installation
Fused Solar and Roofing holds Florida roofing (CCC1331058), electrical (EC13014750), and building (CBC1252064) licenses, all three in-house, and has served Hillsborough, Pinellas, Pasco, and Manatee counties since 2007. Fused Solar and Roofing is an EnergySage Elite Installer with a 5.0/5 rating and 21+ verified reviews, independent verification, earned not purchased. Request a free site survey and solar quote at https://fusedsolarandroofing.com/solar-installation
