Solar Panel Savings Calculator
Estimate your annual solar savings and net yearly return after accounting for installation costs and the federal tax credit. Use this when comparing solar quotes or deciding whether rooftop solar makes financial sense for your home.
About this calculator
This calculator estimates the annual net savings from a residential solar installation. Energy produced each year equals system size (kW) × daily sun hours × 365 days, and the value of that energy is found by multiplying by your electricity rate ($/kWh). The after-tax installation cost is reduced by the federal tax credit: net cost = installationCost × (1 − taxCredit). That net cost is then amortized over a 25-year panel lifespan. The core formula is: annualNet = (systemSize × sunHours × 365 × electricityRate) − ((installationCost − (installationCost × taxCredit)) / 25). A positive result means you save money every year on a levelized basis. Actual savings vary with utility rate inflation, local incentives, and panel degradation over time.
How to use
Suppose you install a 7 kW system at $21,000, your electricity rate is $0.14/kWh, you get 5 daily sun hours, and the federal tax credit is 30% (0.30). Annual energy value = 7 × 5 × 365 × $0.14 = $1,789. Net installation cost = $21,000 − ($21,000 × 0.30) = $14,700. Amortized annual cost = $14,700 / 25 = $588. Annual net savings = $1,789 − $588 = $1,201. You are effectively saving over $1,200 per year on a levelized basis across the system's life.
Frequently asked questions
How does the federal tax credit affect my solar panel payback period?
The federal Investment Tax Credit (ITC) directly reduces the net cost of your system. At 30%, a $20,000 installation effectively costs $14,000 after the credit is applied on your tax return. This lower net cost means the amortized annual burden is smaller, so your annual savings are higher and the simple payback period shortens considerably. Always confirm the current ITC percentage with the IRS or a tax professional, as it can change with legislation.
What daily sun hours should I use when calculating solar savings?
Daily sun hours (also called peak sun hours) represent the equivalent number of hours per day that sunlight intensity averages 1,000 W/m², not just daylight hours. The US average is roughly 4–6 hours, but it varies from about 3 hours in cloudy northern states to over 7 in the Southwest. You can look up your location's value from NREL's PVWatts tool or a solar irradiance map. Using an accurate local figure is the single biggest factor in getting a realistic savings estimate.
Why is the installation cost divided by 25 years in the solar savings formula?
Dividing by 25 converts the one-time capital expense into an annual levelized cost, making it directly comparable to the annual energy value you produce. Most solar panels carry a 25-year performance warranty, making this a standard planning horizon for residential systems. This approach does not account for the time value of money; a more rigorous analysis would use net present value (NPV) or internal rate of return (IRR). However, the simplified annual net figure is a practical starting point for quick comparisons between quotes.