Solar Panel Savings Calculator

Going solar raises three financial questions at once: what the system costs upfront, how long it takes to pay for itself, and what it saves you over 25 years. The tool addresses all three. Note that the 30% federal residential clean energy credit (Section 25D) ended for systems placed in service after December 31, 2025 under the One Big Beautiful Bill Act, so 2026 projections rely on the state and utility incentives you qualify for instead.

System size comes from your monthly bill divided by your rate, which gives the kWh you use; the annual kWh is then divided by the region's sun hours (3.5 to 5.5 a day) × 365 × 0.80, the calculator's allowance for system losses. The size in watts times your cost per watt (default $3.50, in the middle of the $3 to $4 range where most states' median 2025 residential prices fell in Lawrence Berkeley National Laboratory's 2026 data update) gives the gross cost. The federal credit field starts at 0% because the 25D credit ended with 2025, and the state incentive field takes a dollar amount that is subtracted. Annual savings are taken as your full current bill × 12, the payback period is net cost ÷ annual savings, and the 25-year figure is 25 years of savings minus the net cost, with flat electricity prices and no panel degradation.

Accuracy here depends on two inputs: a realistic average monthly bill and the specific state and local incentives that apply where you are, both of which can swing the numbers considerably. Rising utility rates over the years also work in your favor, steadily widening the gap between what you would have paid the grid and what your panels produce.