Solar Panel Cost Calculator
Enter your system size, or let the calculator size a system from your yearly electricity use, to estimate how many panels you need, what the installation might cost and how much power it could make in a year. Every number is editable and everything runs in your browser.
Amounts are in US dollars. The starting values are placeholders, so replace them with your own numbers and quotes.
Enter your values and press Calculate.
Solar panel installation cost calculator: how it works
This solar panel installation cost calculator multiplies the size of the system by a price per watt and adds any other upfront costs. Typical 2026 US installed prices are often quoted around $2.50 to $3.50 per watt before incentives. The default of 2.75 is only a placeholder, so replace it with the figure from your own quote.
- Gross cost = system kW x 1000 x cost per watt + other upfront costs
- Net cost = the larger of 0 and (gross cost – incentives and rebates)
- Net cost per watt = net cost / (system kW x 1000)
- Estimated annual output (kWh) = system kW x peak sun hours x 365 x system efficiency / 100
How many solar panels do I need?
If you pick the second mode, the calculator works backwards from your yearly electricity use. Required kW = annual use / (peak sun hours x 365 x efficiency / 100). The number of panels is the required kW x 1000 divided by the wattage of one panel, rounded up to a whole panel. The system size then becomes panels x panel wattage / 1000, so it can be a little larger than the bare minimum.
In the first mode you enter the system size yourself, and the panel count is shown for information only.
How to use this solar panel cost calculator
- Choose a mode. Enter either the system size in kW or your annual electricity use in kWh from your bills.
- Enter the peak sun hours for your location. They vary across the US, roughly from 3.5 to 7 hours a day, so enter your own.
- Check the efficiency, panel wattage and cost per watt. Add other upfront costs and any incentives you expect.
- Press Calculate or Enter. Reset restores the starting values.
Annual output and efficiency
The annual output follows the common NREL PVWatts-style approach: kW x peak sun hours x 365 x system efficiency. PVWatts’ default system losses are 14%, while this tool uses 80% overall efficiency as a placeholder. Peak sun hours and real losses depend on your location and your setup, so change both boxes to suit.
Incentives
The 30% federal residential solar tax credit (Section 25D) for homeowner-owned systems ended for systems installed after December 31, 2025, so the incentive default here is $0. State, utility and local incentives vary, so check your own and ask a tax professional. Leases and power purchase agreements work differently and are not covered here.
Worked example
An 8 kW system at 2.75 per watt costs 8 x 1000 x 2.75 = 22,000 before other costs. With 4.5 peak sun hours and 80% efficiency it makes about 8 x 4.5 x 365 x 0.8 = 10,512 kWh a year, and with 400 W panels you would need 20 of them. If you add 1,000 of other upfront costs and 2,000 of incentives, gross cost is 23,000 and net cost is 21,000.
In the second mode, 6,000 kWh of yearly use needs 6000 / 1314 = 4.57 kW, which rounds up to 12 panels. The system is then 12 x 400 / 1000 = 4.8 kW and costs 13,200.
Assumptions & limits
- All figures are estimates, not financial, tax or engineering advice.
- Shade, roof direction, tilt and local rules change real results. The calculator uses one overall efficiency figure for all of that.
- Panels typically lose about 0.5% of output per year. This calculator does not apply that loss to the yearly output, but the Solar Payback Calculator can.
- Prices, incentives and rules change, and they differ by place, so check current quotes and rules where you live.
Frequently asked questions
How much does a solar panel system cost?
It depends on the size and on the quote you get. Prices are often quoted around $2.50 to $3.50 per watt before incentives, so use your own quote in the cost per watt box.
Is there still a federal tax credit?
The 30% residential credit (Section 25D) for homeowner-owned systems ended for systems installed after December 31, 2025. State, utility and local incentives vary, so check yours and ask a tax professional.
What are peak sun hours?
They are the equivalent number of hours per day with full sunlight strength. They vary by place, roughly from 3.5 to 7 hours a day in the US, so enter the value for your location.
Why does the panel count round up?
You cannot install part of a panel, and rounding down would leave the system a little short of your target.
Why is efficiency 80%?
It is a placeholder for overall system efficiency. PVWatts’ default system losses are 14%, so you can compare, and you can enter any value from 1 to 100.
Does this cover leases and power purchase agreements?
No. Leases and PPAs work differently, so this tool only covers a system you buy.
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Last updated: October 2026