Solar Panel Savings Calculator
Estimate solar system size, panel count, net cost after the 30% federal tax credit, payback years, and 25-year savings.
How to use this solar panel savings calculator
Solar math is: how many kWh you buy, how much sun you get, and what installed watts cost after the federal investment tax credit (ITC), currently 30% for qualifying residential systems. Inverters, roof age, HOA, and net-metering rules change the real payback. This solar panel savings calculator uses a 0.77 derate for dirt, heat, and wiring.
Peak sun hours are not clock hours. The Southwest may see ~6; the Northeast ~3.5–4.5. Get a shade study. If your roof is due for shingles, do the roof first. Degradation of about 0.5%/year is folded into the 25-year figure.
Formula
Worked example
A $165 bill at $0.16/kWh in 4.8 sun hours often sizes near a mid-size rooftop array, with simple payback commonly in the high single to low double digits of years after the 30% credit.
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Frequently asked questions
How many solar panels do I need?
Divide required system watts by the panel wattage (often 400 W). A 8 kW system is about 20 panels.
What is the 30% tax credit?
The federal ITC can subtract 30% of a qualifying installed cost from your taxes, not from the invoice at the hardware store. It is not cash back if you owe no tax.
How long is solar payback?
Often 6–12 years where rates are high and sun is decent. Poor net metering stretches it.
Does this include batteries?
No. Storage adds cost and resilience. Size batteries from overnight essential loads, not from this PV-only math.
Will I wipe the whole bill?
Usually 80–100% of annual kWh if the array and interconnection allow. Seasonal bills still vary.
Is the 30% solar tax credit still available?
This tool uses a 30% federal ITC on qualifying installed cost. Confirm current IRS rules and that you have tax liability to use it.
Results are estimates for informational purposes and are not financial, legal, or professional advice. Last reviewed 2026-08-20.