$180/mo bill at $0.16/kWh
~1,125 kWh/mo usage, south roof 400 sq ft usable.
System sizes to roof or usage cap — payback often 9–12 years before incentives beyond 30% credit.
Calculator · Free
Solar Panel Payback Calculator
Estimate system size from your bill and roof, installed cost, annual savings, and payback — with utility rate sourced to EIA averages.
Simple payback (after 30% credit)
10.4 years
~0.7 kW system · $138/yr savings at your rate
- Estimated install
- $1,806–$2,360
- Federal credit (30%)
- −$616
- Net cost
- $1,436
- Est. production
- 864 kWh/yr
Rate source
Default rate ~$0.16/kWh follows EIA U.S. average residential retail electricity price (2024). Enter your bill’s $/kWh for accuracy. Source: U.S. Energy Information Administration, Electric Power Monthly, residential sector average.
What this assumes
- Production uses ~1,200 kWh per kW-year before orientation adjustment — typical U.S. residential average.
- Installed cost near $2.85/W before incentives; net metering policy is not modeled.
- Default $/kWh follows EIA U.S. residential average retail price (~16¢/kWh, 2024); override with your utility bill.
Important
Utility net metering rules, demand charges, and HOA restrictions change economics. Get a site-specific production report from an installer.
Understanding the result
Rate matters as much as sun
High retail electricity prices shorten payback even on moderately shaded roofs. Enter your all-in $/kWh from a recent bill.
Federal credits change net cost
The residential clean energy credit has been 30% for qualifying systems — apply credits to net cost, not monthly payment alone.
How the math works
Monthly bill and $/kWh imply annual kWh. System kW is min(roof-limited kW, usage-based kW). Production ≈ 1,200 kWh/kW-year × orientation factor. Savings = production × rate. Net cost subtracts 30% federal credit illustration. Payback = net ÷ annual savings.
Where to find each input
- Electric bill kWh or total ÷ rate
- Usable roof area excluding vents and shade
- Azimuth from site survey or satellite
Worked examples
High rate $0.28/kWh
Same usage.
Payback shortens materially — rate entry dominates.
East-facing array
Orientation factor ~0.82.
More panels needed for same kWh — roof area cap may bind.
What this does not include
- Battery storage
- Demand charges
- Net metering policy changes
- Tree removal
Regional adjustment
Production varies ±15% by state sun resource — installer PVWatts report refines this.
Accuracy and references
Default retail rate cites U.S. EIA Electric Power Monthly, residential average ~16¢/kWh (2024). Install $/W near NREL benchmark ~$2.80–$3.00/W before incentives.
Counterpart bridge
Pricing this on the contractor side?
This page interprets quotes and budgets from the buyer’s chair. The matching pro tool uses the same scope logic to build a defensible price.
Open Dwelling Load CalculatorFor trade owners
Pricing this job as a contractor?
Homeowners see national ranges on this page. If you are building the estimate, use the same scope assumptions — then price to burdened labor, overhead recovery and a real margin.
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Verify any licence yourself before signing: state licensing hub.
Common questions
How long does home solar take to pay back?
Often 8–14 years on utility savings alone after credits, depending on rate, usage, and install price.
What size system do I need?
Divide annual kWh use by ~1,200 kWh per kW, then cap by usable roof area — this tool does both.
Where does the default electric rate come from?
The placeholder follows EIA average U.S. residential retail price; replace with your utility’s $/kWh.
Does orientation matter?
South-facing production is highest; east and west lose roughly 15–20% in this model.
Is battery storage included?
No — batteries add cost and change backup value; not modeled here.
What about HOA rules?
Many states limit solar bans — still review architectural requirements before signing.
Should I buy or lease?
Ownership captures credits and raises resale; leases shift maintenance but complicate sale.
How do I verify production?
Use installer PVWatts or Aurora reports — compare to this estimate before purchase.
Where does default rate come from?
EIA U.S. residential average retail price — replace with your utility $/kWh.
Is 30% credit guaranteed?
Verify current IRS residential clean energy credit rules and income limits.
Net metering?
Export compensation varies by utility — savings may be lower than retail rate in some tariffs.
HOA restrictions?
Many states limit solar bans — still file architectural approval.
Lease vs buy?
Ownership captures credits; leases shift maintenance and transfer complexity.
Roof age?
Replace aging roof before solar if <10 years life left.
Shade trees?
Reduce usable production — site survey required.
Panel degradation?
Not modeled — add 0.5%/yr production loss mentally.
Time-of-use rates?
Shift savings if you export at lower TOU credit.
Verify before signing?
Demand installer production guarantee and equipment spec sheet.
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