Quick answer
An $18,000 system offsetting 90% of a $180/month bill pays back in about 9–10 years with 3% rate increases.
How it works
Solar payback compares the upfront system cost against the electricity bills you avoid. Rising utility rates make each later year of savings worth more.
Formula
Yearly savings = annual bill × offset% × (1 + rate rise)^year; payback when cumulative savings ≥ cost
Assumptions & limitations
- Constant offset percentage
- No financing costs or maintenance included
- Utility rates rise at the entered steady rate
Formula and assumptions reviewed October 2026 by the Calculyn team. How we build our calculators
Frequently asked questions
What incentives apply?
Enter the cost after the federal tax credit and any state/utility rebates for an accurate payback.
Do panels degrade?
Yes, roughly 0.5% output loss per year — most are warrantied for 25 years.