4.2 peak sun hours/day average. Residential electricity rate: 28.42¢/kWh.
Installed cost at 2.75$/W, accounting for 20% system-loss derate (inverter, wiring, soiling, temperature).
| System | Annual kWh | Annual Savings | Installed Cost | Payback |
|---|---|---|---|---|
| 4 kW | 4,909 kWh | $1,395.13 | $11,000 | 7.9 years |
| 6 kW | 7,363 kWh | $2,092.69 | $16,500 | 7.9 years |
| 8 kW | 9,818 kWh | $2,790.25 | $22,000 | 7.9 years |
No incentives assumed: The federal residential solar investment tax credit ended after 2025. Some states and utilities still offer rebates or performance-based incentives; check with your utility.
Full self-consumption or net metering: Savings assume you use all generation on-site or export at retail rates via net metering. Some utilities buy surplus power at wholesale rates, which would reduce savings.
Your site specifics matter: Roof shade, orientation, system degradation, and your actual utility tariff (demand charges, time-of-use rates, fixed fees) can significantly change payback.
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