How solar panel cost is calculated
Price a solar system before you talk to an installer. No signup, no email, and nothing leaves your browser — the numbers below are calculated on your device.
System size × cost per watt, plus fixed costs. The calculator multiplies your system size in kW by your cost per watt — $2.90 is a typical US installed figure in 2026 — then adds any fixed costs such as permits or a main-panel upgrade. An 8.4 kW system at $2.90 per watt costs about $24,360; a 4 kW system about $11,600; a 10 kW system about $29,000.
The split is roughly 60% equipment (panels, inverter, mounting, wiring) and 40% labour, permits and inspection. Premium panels, complex roofs, batteries and panel upgrades push the cost per watt up; simple roofs and competitive quotes push it down.
All figures are post-credit: the US 30% federal residential solar credit ended on 31 December 2025. If your state or utility still offers an incentive, subtract it from your total before comparing quotes.
Worked example: an 8.4 kW system at $2.90 a watt
Take the calculator’s own defaults. An 8.4 kW system at $2.90 per watt costs 8,400 × $2.90 = $24,360.00 in total. With 400 W panels that is 21 panels, or $1,160.00 per panel. The split is $14,616.00 for equipment (60%) and $9,744.00 for labour, permits and inspection (40%). A smaller 4 kW system is the same maths at a smaller size: 4,000 × $2.90 = $11,600. If a quote comes in far above $2.90 a watt, ask the installer to break it down — the gap is usually a battery, a main-panel upgrade, a complex roof, or simply a high margin.
| Cost worked example | Figure |
|---|---|
| System size | 8.4 kW |
| Cost per watt | $2.90 |
| Total installed cost | $24,360.00 |
| Panels | 21 × 400 W |
| Cost per panel | $1,160.00 |
| Equipment (60%) | $14,616.00 |
| Labour, permits and inspection (40%) | $9,744.00 |
| 4 kW system at the same rate | $11,600 |
| 10 kW system at the same rate | $29,000 |
What changes the answer
Cost per watt is a national average, not a quote. A steep, multi-level or slate roof takes longer to work on and costs more per watt than a simple single-storey asphalt roof. Premium panels — higher efficiency, better warranty — add to the equipment line but can be worth it on a small roof where every watt counts. A battery is the biggest single extra: it can add several thousand dollars and is priced separately from the panels. Older homes often need a main-panel upgrade too, and permits vary by city and utility. The honest way to use this calculator is to set your own cost per watt from a real quote, then change the system size and watch the total move. Three written quotes from local installers, compared line by line, still beat any online estimate.
Need the full picture? Use the solar panel calculator to size your system first, then the installation cost breakdown and the payback calculator.
Sources
- U.S. Department of Energy — solar energy basics, system pricing and homeowner guidance.
- EnergySage — US solar costs per watt by state and system size.
- Solar Energy Industries Association (SEIA) — US solar market data and policy, including the federal tax credit.
By Shehzad Hussain. Published November 9, 2026. Last updated November 11, 2026.