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Solar Panel Cost Calculator
Enter your system size and cost per watt. The calculator shows you gross cost, your 30% federal credit, and what you actually pay.
By Jessica Martinez · Updated June 2026
Enter your system size and cost per watt. The calculator shows you gross cost, your 30% federal credit, and what you actually pay.
Planning figure only. Your roof, equipment tier and installer overhead all move the real number.
The calculator multiplies your system size in watts by your cost per watt to get the gross price, then applies the 30% federal tax credit to show what you actually pay. That is the entire formula: two multiplications, no hidden steps.
Using the default inputs above, an 8 kW system at $3.00 per watt comes to a $24,000 gross price. Apply the 30% credit and the net drops to $16,800, which works out to $2.10 per watt after incentives. Change the wattage price or system size and every figure on this page recalculates the same way.
| System size | Gross cost | Net after 30% credit |
|---|---|---|
| 4 kW | $12,000 | $8,400 |
| 8 kW | $24,000 | $16,800 |
| 10 kW at $3.50/W | $35,000 | $24,500 |
Punch any of those three rows into the calculator above and you will land on the same numbers, since the table is just the calculator's own math run at fixed inputs.
Cost per watt is the number to anchor on when you compare bids, not the sticker price alone. A larger system naturally costs more in total even at a lower per-watt rate, so two quotes only compare fairly once you divide out the system size. Installers who lead with a monthly payment figure are frequently the ones omitting both the gross price and the per-watt rate from the conversation.
Once you know your gross and net cost, the next question is usually how fast that cost pays for itself and how many kilowatts your roof actually needs. The savings calculator and system size calculator pick up from here.
Solar is priced per watt installed. Multiply by your system size to get the gross cost, subtract 30% for the federal credit, and that is your net cost. An 8 kW system at $3/watt comes to $24,000 gross and about $16,800 after the credit. Cost per watt is the number to focus on when comparing quotes. Installers who present only a monthly payment are omitting both of those figures on purpose.
Typically $2.50 to $3.50 per watt installed. An 8 kW system runs $20,000 to $28,000 before the 30% federal credit, which reduces that to $14,000 to $19,600.
The federal Residential Clean Energy Credit reduces your federal tax bill by 30% of your total system cost, dollar for dollar. On a $24,000 system that is $7,200 off what you owe.
Yes. Installer quotes are generally all-in per watt: equipment, labor, permits, and interconnection fees. Confirm this with each installer before comparing numbers.
No. This is a planning estimate. Get at least three quotes from local installers before committing to anything.
At $3.50 a watt, a 10 kW system prices out around $35,000 before incentives. Since a system that large usually skips the credit only if it is for a business, a homeowner applying the 30% credit would net closer to $24,500. Run your own wattage price above to see the exact split.