Rex says
Money math without the spreadsheet headache. Plug in your numbers and I'll show you exactly where the dollars land.
Try a scenario
Click to load — tweak from there.Inputs
Result
Net cost after tax credit
$16,800
Gross installed cost
$24,000
Tax credit amount
$7,200
Net cost per watt
$2.10
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How to use this
- 1Enter system size (kW).
- 2Enter installed rate per watt ($/W).
- 3Enter federal/state tax credit (%).
- 4Read your net cost after tax credit on the right — it updates as you type.
- 5Hit Share to keep the scenario or send it to someone.
About this calculator
Residential solar cost is quoted almost universally as a price per watt of system capacity, which already bundles panels, inverter, racking, and installation labor, then reduced substantially by the federal solar Investment Tax Credit and any state or utility incentives. This calculator prices a system by multiplying system size in kilowatts by a per-watt installed rate, then subtracts the federal tax credit percentage to show your realistic net cost after incentives. 2026 US national averages run about $2.60-$3.50 per watt installed before incentives, meaning a typical 8kW residential system (roughly enough to offset an average home's usage) runs about $21,000-$28,000 before credits. The federal residential solar tax credit has historically been 30%, though check current-year IRS guidance since credit percentages and eligibility can change by legislation — always confirm the exact rate in effect for your install year and consult a tax professional, since this calculator provides an estimate only, not tax advice.
Worked example
Using the values the calculator loads with:
Inputs
- System size: 8 kW
- Installed rate per watt: 3 $/W
- Federal/state tax credit: 30 %
Results
- Net cost after tax credit: $16,800
- Gross installed cost: $24,000
- Tax credit amount: $7,200
- Net cost per watt: $2.10
What each field means
Inputs
- System size (kW)
- The system size used in the calculation, measured in kW. Starts at 8 kW so you have a working example on load. Accepted range: 2–25 kW.
- Installed rate per watt ($/W)
- The installed rate per watt used in the calculation, measured in $/W. Starts at 3 $/W so you have a working example on load. Accepted range: 1.5–5 $/W.
- Federal/state tax credit (%)
- The federal/state tax credit used in the calculation, measured in %. Starts at 30 % so you have a working example on load. Accepted range: 0–50 %.
Results
- Net cost after tax credit
- Returned as a money amount in US dollars and shown as the headline result. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Gross installed cost
- Returned as a money amount in US dollars. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Tax credit amount
- Returned as a money amount in US dollars. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Net cost per watt
- Returned as a money amount in US dollars. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
FAQ
How is residential solar system size determined?
An installer sizes your system based on your annual electricity usage (from utility bills), your roof's usable sun-facing area, and local peak sun hours — the goal is typically to offset most or all of your annual usage, though some homeowners intentionally undersize to reduce upfront cost.
Does the federal tax credit apply to the full system cost?
Generally yes, including panels, inverter, racking, and labor, and in many cases battery storage installed alongside the system — but the credit reduces your tax liability rather than being an upfront rebate, so you need sufficient tax liability to fully use it, and rules can change, so confirm current details with a tax professional.
Are batteries included in typical solar installation quotes?
Not usually — battery storage (like a Tesla Powerwall or similar) is typically quoted and priced separately, commonly adding $10,000-$18,000 to a system, and is optional unless you need backup power during outages or live somewhere without reliable net metering.
How long is the payback period for residential solar?
Typical US payback periods after incentives run 6-12 years depending on local electricity rates, sun exposure, and financing method, with systems generally warrantied and expected to perform for 25+ years — meaning most homeowners see well over a decade of savings after payback.
Accuracy and limitations
- Results are estimates before tax, fees, and inflation unless an input explicitly covers them.
- Rates are treated as fixed for the whole period — variable-rate products will drift from this projection.
- This is educational maths, not financial advice. Check anything contractual with the lender or your accountant.
Related tools
Cite this calculator
Writing about this topic? Grab a citation — every link helps keep these tools free.
RevenueLab. (2026). Solar Panel Installation Cost Calculator. Retrieved from https://www.revenuelab.fyi/toolbox/solar-panel-installation-cost
<p>Source: <a href="https://www.revenuelab.fyi/toolbox/solar-panel-installation-cost" target="_blank" rel="noopener">Solar Panel Installation Cost Calculator — RevenueLab</a> (2026).</p>
Source: [Solar Panel Installation Cost Calculator — RevenueLab](https://www.revenuelab.fyi/toolbox/solar-panel-installation-cost) (2026).