Solar Basics
Solar Panel Degradation: What It Means for Long-Term Production
Understand why solar output changes gradually over time, how degradation appears in an estimate, and which warranty details homeowners should compare.
Quick answer
Solar modules normally produce less energy over time, which is why a credible long-term estimate states its degradation assumption instead of treating year-one output as permanent.
Degradation is a planning assumption
A production model starts with expected first-year kilowatt-hours and then applies a gradual output change over later years. The exact rate depends on the equipment, climate, installation, and model—not a universal promise.
Read a performance warranty closely
A panel performance warranty commonly describes a minimum output threshold at future dates. It is different from a product warranty, and it may not cover labor, shipping, or every cause of lower production.
Compare estimates on the same timeline
Ask each provider to state annual production, degradation, utility-rate assumptions, and maintenance assumptions. A 25-year savings chart is useful only when its inputs are visible.
Watch for a sustained change
Weather and seasons naturally change output. Compare similar months or the documented model before assuming a fault, and use monitoring records when requesting service.
Research and review
Reviewed for plain-language accuracy, source links, and consistency with SolarSavings calculator assumptions.
Reviewed by SolarSavings.energy Research Desk
Last reviewed August 14, 2026
This is educational content, not tax, legal, engineering, or financial advice. Confirm current incentives, tariffs, and contract terms with the relevant provider or qualified professional.
Frequently asked questions
Do solar panels stop working after 25 years?
Not necessarily. A 25-year warranty is not an expiration date; output and warranty terms should be checked for the specific equipment.
Can cleaning fix degradation?
Cleaning can address surface soiling in some situations, but it does not reverse long-term module aging.
What degradation rate should I use?
Use the rate stated in the equipment documentation or production model, then compare it consistently across proposals.
Primary sources
This guide was written for homeowners and reviewed against the following government and research resources. Programs and utility rules can change, so verify current details before making a financial decision.