How a Solar System Is Sized in Florida: Bills, Not Roof
The most common mistake in a Tampa Bay solar quote is sizing the system to the roof. A roof that holds thirty panels gets thirty panels, the homeowner pays for thirty, and a third of what they produce goes back to the utility at a fraction of what the homeowner pays for power. Fused Solar and Roofing sizes a system from twelve months of the home's actual utility bills, designs to the usage, and then checks the roof can hold it. The number of panels is the output of that process, not the input. Fused Solar and Roofing is a licensed roofing (CCC1331058), electrical (EC13014750), and building contractor (CBC1252064), all three in-house.
1. Why the bills come first
A solar system in Florida is worth most when the home uses what it makes. Power the array produces and the house consumes at the same moment replaces electricity the homeowner would have bought at the full retail rate. Power the array exports to the grid earns a credit, but under the utilities' current rules that credit is worth less than retail, and a system that routinely exports a large share of its output is a system the homeowner overpaid for. Twelve months of bills show how much the home uses, when, and how it swings from April to October, and the system is designed to cover that.
Fused does not quote from a single bill or from the square footage. It asks for the full year because a Tampa Bay home's July usage can be twice its February usage, and a system sized to either one alone is wrong.
🔑 Key Takeaway: The system is sized to what the house uses over a year, so the homeowner is not paying for production the utility buys back at a discount.
2. Reading a year of usage
The bills give monthly kilowatt-hours. Fused totals the year, looks at the summer peak and the winter trough, and asks about anything that will change: a pool pump going in, an electric vehicle coming, a second air handler, a retirement that puts people home all day, children leaving. The design target is the annual usage after those changes, produced over a year by an array on this roof with its particular orientation, pitch, and shade. Tampa Bay production per installed kilowatt is well understood, and the estimate on the proposal is the array's expected annual output against the home's expected annual usage.
💡 Pro Tip: Download your last twelve months of bills from your utility's website before the first conversation, and tell the designer about any appliance or vehicle you plan to add. Usage, not roof size, sizes the system, and having the numbers turns a sales call into a design call.
3. Then the roof
With the target set, the design goes to the roof: which planes face south, west, and east, what the pitch is, where the shade falls at different times of day, where the vents and skylights are, and how many panels fit with the access pathways and setbacks the Florida Building Code requires. If the usable planes hold the target, the design is done. If they hold less, the system is the size the roof allows and the proposal says what share of usage it covers. If they hold more, the extra space stays empty, because panels the house cannot use are cost, not value.
Fused's standard panel is the JA Solar 440W bifacial, and the inverter is chosen for the plane count and the shade: a string inverter on one open plane, microinverters or optimizers on a split or partly shaded array.
4. When sizing up makes sense
A known future load: an EV on order, a pool under construction, a planned addition. Those are designed in now rather than added later, because adding panels later means a second permit, a second inverter sizing question, and a second day on the roof. A battery, which changes the arithmetic because stored production is used at home instead of exported, and a larger array can make sense with one. And a homeowner who simply wants to cover every kilowatt-hour including the summer peak, understanding that some winter production will export, which is a legitimate choice as long as it is made with the numbers in front of them.
What does not justify sizing up is a salesperson's commission on a bigger system.
5. When sizing down makes sense
A roof whose only good plane is small. A budget that fits a system covering seventy percent of usage comfortably and a hundred percent uncomfortably. A home with heavy shade on part of the roof, where the shaded panels would produce too little to justify their cost and the honest design leaves them off. Fused shows production by plane so the homeowner can see what a north-facing or shaded section would actually contribute and decide.
⚠️ Warning: A proposal that fills every square foot of roof and quotes production as if all of it faces south is the most common oversell in Tampa Bay. Ask for the production estimate by roof plane.
6. What the proposal shows
The home's annual usage from the bills. The proposed system in panels and kilowatts. The expected annual production and the share of usage it covers. The layout by roof plane. The price at $1.85 per watt installed with any two-story, steep-pitch, or roof-type adder as its own line. The warranty terms. And the utility's interconnection step, which Fused files after the inspection; the system stays off until the utility sets the meter.
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. Sizing when the roof is also being replaced
When the roof is being replaced with the solar, the sizing question is the same but the roof constraint relaxes a little: vents and penetrations can be relocated during the re-roof to open up a plane, and the mounts go into the new roof wherever the design calls for them. Fused Solar and Roofing is a licensed roofing (CCC1331058), electrical (EC13014750), and building contractor (CBC1252064), all three in-house. The roof and the solar are quoted together as two lines, and the system is still sized from the bills.
8. Why homeowners have Fused size the system
Because Fused is paid for installing a system that fits the house, not for selling the biggest one the roof holds, and because the same company will be servicing the system and, eventually, replacing the roof under it, so it has every reason to get the size right the first time. Fused has designed systems from the bills across Tampa Bay since 2007.
🔑 Key Takeaway: Twelve months of bills set the target, the roof confirms the fit, and the panel count falls out of that. Any quote that starts from the roof has it backwards.
Ready to see what your bills say the system should be? Request a free solar quote at https://fusedsolarandroofing.com/solar-installation
Frequently Asked Questions
How many solar panels do I need for my house in Florida?
It depends on your annual usage, not your roof. Fused sizes from twelve months of utility bills, then checks the roof holds it. A typical Tampa Bay home lands between 20 and 26 panels of 440W, 8.8 to 11.44 kW, but the bills decide.
Why not fill the whole roof with panels?
Because production the house cannot use is exported to the utility at a credit worth less than the retail rate, so panels beyond the home's usage cost more than they return.
What information do I need for a solar quote?
Twelve months of utility bills and a list of anything that will change your usage: an EV, a pool, an addition, more people at home. Fused designs to the usage after those changes.
Should I size my solar system bigger for a future electric vehicle?
Yes, if the vehicle is planned. Designing the load in now avoids a second permit and a second day on the roof later.
Does a battery change how the system is sized?
It can. Stored production is used at home instead of exported, so a larger array can make sense with a battery. Fused runs the numbers both ways.
How does Fused handle shaded or north-facing roof sections?
It shows production by plane and usually leaves sections off that would not produce enough to justify their cost, rather than filling them and quoting as if they faced south.
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 solar quote at https://fusedsolarandroofing.com/solar-installation
