Panel count, DC wattage, mounting hardware and cost for a rooftop solar array.
Estimates are planning aids, not a professional quote. Double-check quantities and product coverage — and any local code or permit requirements — before you buy.
⚠ This is a planning-level material takeoff, not an engineered or PE-stamped design. Roof structural capacity, exact attachment spacing and wire sizing must be verified by your installer or a licensed engineer against your specific rafters, snow load and local code before permitting.
⚠ Grid-tied solar requires a permit, an interconnection agreement with your utility, and in most jurisdictions a licensed electrician to make the panel connection and sign off before you energize the array. Budget for inspection and utility approval time on top of the physical install.
| Electrical | $6,376–$8,627 |
| Connectors & Brackets | $1,855–$2,509 |
| Total | $8,231–$11,136 |
Excludes tools, delivery, tax and permit fees. Labor not included — this is a DIY materials estimate.
These are affiliate links: we may earn a commission if you buy through them, at no extra cost to you. It never changes what the calculator recommends — the shopping list comes from your dimensions, not from what pays.
About this calculator
Enter your household's annual electricity usage, your area's peak sun hours, and how much of that light your system actually converts, and the Solar Panel Calculator sizes a real rooftop array: total panel count and DC wattage, then the mounting hardware a crew bolts down row by row — racking rail cut to the run length, flashed roof attachments landed on your rafter spacing, and the mid and end clamps that lock every panel to the rail.
Choose microinverters or a string inverter with power optimizers and the parts list and the wiring both change with it, then dial in the conduit run to your main panel and it sizes the breaker, wire gauge and even checks whether your panel's busbar has room for the backfeed under the 120% rule. It's a planning estimate for shopping and budgeting, not a substitute for your installer's engineered design.
Step by step
A step-by-step walkthrough to go with your plan above. Follow the product instructions and any local code or permit requirements as you work.
Use the calculator to turn your annual usage and local sun hours into a target DC kilowattage, then round to a whole panel count at the wattage you're buying. This number drives every other line on the page.
Walk the roof plane and mark out rows around vents, chimneys and valleys, keeping each run to a length your racking manufacturer rates for continuous rail. Confirm the plane gets enough sun hours to justify the layout before you drill anything.
Find the rafters with a stud finder or from the attic, mark the attachment spacing along each rail line, and set each standoff with proper flashing or a purpose-built clamp for your roof type. This is the step a leak traces back to if it's rushed.
Bolt the racking rail to the attachments, level and square across the whole row, then set each panel with mid clamps between modules and end clamps at both ends of the run.
Land microinverters under each panel or wire the string through the power optimizers, then home-run the AC or DC output to a single combiner point on the roof, keeping every splice weatherproof.
Bend and strap conduit from the roof combiner down the exterior wall to the main panel or a dedicated backfeed breaker location, then pull the sized conductors through in one pass.
Mount the utility-required AC disconnect within sight of the meter, then have a licensed electrician land the backfeed breaker and confirm it fits under your panel's 120% busbar rule.
Schedule the electrical and structural inspections, then wait on your utility's interconnection agreement before you energize the array — most utilities require their sign-off before you're allowed to backfeed the grid.
Equip the job
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Decks & Structures
Answers
It comes down to your annual electricity usage, your area's average peak sun hours, and how much the system loses to wiring, inverter conversion and panel derating — typically 15–25%. Divide your daily kWh need by the effective sun-hours after that loss, and that's the DC kilowatts your array has to produce; divide by the wattage of the panel you're buying and round up for the panel count. A typical U.S. home using about 10,800 kWh a year lands around 15–25 panels depending on sun hours and panel wattage, which is what this calculator works out directly.
Microinverters convert DC to AC at each panel, so one shaded or failing panel doesn't drag down the whole array's output, and there's no single point of failure — but you're buying one inverter per panel. A string inverter is one central unit, generally cheaper up front, paired with power optimizers at each panel for the module-level rapid shutdown most code now requires, which also recovers some of microinverters' shade tolerance and per-panel monitoring. Microinverters tend to win on roofs with any shading or multiple orientations; string-plus-optimizers wins on a simple, unshaded, single-plane roof.
Yes, in nearly every U.S. jurisdiction. You'll need a building permit for the structural and electrical work, an inspection before the system is energized, and a signed interconnection agreement with your utility before you're allowed to backfeed power onto the grid, which is what actually enables net metering credit. Most utilities also require a licensed electrician to make the final panel connection. Budget real time for permitting and utility approval — it routinely takes longer than the physical install itself.
Possibly, if your main panel's busbar is already close to its rating. Code generally caps the sum of your main breaker and the new solar breaker at 120% of the busbar's rating, so a 200A panel typically has only about 40A of headroom for a backfed solar breaker no matter how much physical space is left in the box. If your array's inverter output exceeds that, the fix is usually a line-side tap ahead of the main breaker, a busbar upgrade, or sizing the array down — this calculator flags it against your panel size automatically.
Materials alone for a residential DIY system typically run about $1.00–$1.50 per watt — panels, racking, inverters or microinverters, wiring and conduit — before permits, an electrician's interconnection work, or a battery, any of which adds significantly more. A 7–8 kW system, enough to offset a typical household's usage, usually lands in the $8,000–$12,000 range in materials. A fully licensed, professionally installed system costs two to three times that once labor, overhead and margin are added on top.