Solar Panel โ ROI & Payback
Calculate system size, cost, payback period, and 25-year savings.
Why This Scientific Calculation Matters
Why: Solar panels can reduce or eliminate electric bills. Payback depends on system cost, sun hours, and electric rates.
How: Enter monthly bill, roof size, sun hours, panel cost per watt, and electric rate. The calculator estimates system size and payback.
- โHigher electric rates = faster payback
- โSouth-facing roofs produce most
- โ30% federal tax credit reduces cost
Sample Scenarios โ Click to Load
Inputs
โก Inputs
ROI Analysis
Input
Results
๐งช Scientific Discoveries
Typical US home needs 5โ7 kW system
โ DOE
Payback usually 7โ12 years
โ NREL
30% federal tax credit (check current)
โ IRS
๐ Key Takeaways
- โข Solar panel systems typically need 5โ7 kW for average US homes
- โข Payback period is usually 7โ12 years depending on location and incentives
- โข Sun hours vary by location: 4โ7+ peak hours per day in the US
- โข Federal tax credits can reduce system cost by 30% (check current programs)
- โข Panels often last 25+ years with minimal degradation
๐ก Did You Know?
๐ How It Works
Annual kWh = (monthly bill / electric rate) ร 12. System size (kW) = annual kWh / (sun hours ร 365). Total cost = system kW ร 1000 ร $/watt. Payback = total cost / annual savings. 25-yr savings = annual savings ร 25.
๐ฏ Expert Tips
Get multiple quotes
Prices vary by installer
Check incentives
Federal, state, utility rebates
South-facing
Best production in N hemisphere
Shade matters
Trim trees, avoid obstructions
โ๏ธ Location Comparison
| Location | Sun hrs | Payback |
|---|---|---|
| Southwest | 6โ7 | ~7 yrs |
| Southeast | 5โ6 | ~8โ9 yrs |
| Midwest | 4โ5 | ~10 yrs |
| Northeast | 4โ5 | ~10โ12 yrs |
โ FAQ
What are sun hours?
Peak sun hours are equivalent hours of full sunlight per day. A location with 5.5 sun hours gets the same energy as 5.5 hours of noon sun. Varies by latitude and weather.
How much roof space do I need?
Roughly 15โ20 sq ft per kW. A 6 kW system needs ~100โ120 sq ft. South-facing, unshaded roofs work best.
What affects payback period?
Electric rates, sun hours, system cost, and incentives. Higher rates and more sun = faster payback.
Do panels work in cloudy areas?
Yes, but output is lower. Cloudy regions may need larger systems or longer payback periods.
What about battery storage?
This calculator assumes grid-tied. Batteries add cost; model separately for backup/off-grid.
Include tax credit?
Multiply total cost by 0.7 if 30% credit applies. Check current IRS rules.
๐ Stats
๐ Sources
๐ Calculation Method
Annual kWh = (monthly bill / electric rate) ร 12. System size (kW) = annual kWh / (sun hours ร 365). Total cost = system kW ร 1000 ร $/watt. Payback = total cost / annual savings.
โ ๏ธ Disclaimer: Estimates only. Actual costs, production, and payback vary. Get professional quotes. Incentives change. Not financial advice.
For educational and informational purposes only. Verify with a qualified professional.
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