What really drives solar savings
Solar savings come down to a simple trade: you pay for a system once, and in return you stop buying decades of electricity from your utility. Whether that trade is a good one depends on four variables — how much sun your roof gets, how much you pay per kilowatt-hour today, how fast those rates rise, and what you pay for the system after incentives. This calculator models all four over a 25-year horizon so you can see the full picture rather than a single first-year number.
Important 2026 update: the homeowner tax credit has ended
For more than a decade the 30% federal Residential Clean Energy Credit (Section 25D) was the biggest lever in solar economics. That changed on January 1, 2026. Under the One Big Beautiful Bill, signed July 4, 2025, the homeowner credit was terminated for any system placed in service after December 31, 2025 — so a home solar system you buy with cash or a loan in 2026 receives $0 in federal credit. Many competing calculators still quietly apply 30%, which now overstates savings by thousands of dollars. We default to the correct 2026 rules and only apply the credit if you specifically model a system that was placed in service in 2025 or earlier. One nuance worth knowing: leases and power-purchase agreements can still pass through federal value, because the third-party owner claims the separate commercial 48E credit.
Why we escalate rates and degrade production
Two long-run effects pull in opposite directions. Utility electricity prices have risen roughly 2.5% per year over the long term, which makes each kWh your panels produce more valuable as time goes on. Working against that, solar modules lose about 0.5% of their output annually as they age. A credible savings model has to account for both, which is why our year-by-year table shows production gently declining while the value of each kWh climbs. The net effect for most homeowners is still strongly positive.
Payback, ROI, and NPV — three lenses
We report three complementary metrics. Payback period tells you when cumulative savings cover your net cost — intuitive, but it ignores everything after that date. ROI expresses lifetime net profit as a percentage of what you put in. Net present value is the most rigorous: it discounts every future dollar of savings back to today (we use 4%) so you can compare solar against simply investing the money. A positive NPV means the panels beat that alternative.
Net metering is the wildcard
How your utility credits the energy you export to the grid can swing savings by thousands of dollars. Under full retail net metering, every exported kWh offsets one you would have bought. Under newer net-billing tariffs, exports may be worth only a fraction of retail, which rewards self-consumption and batteries. Check your state’s rules in our Incentive Finder, then revisit this calculator with a realistic export assumption.
As always, treat these figures as a well-informed estimate. Final numbers depend on a professional shade study, your exact rate schedule, and the equipment quoted. But walking into a sales conversation already knowing your payback and ROI is the best protection against an inflated pitch.