Quick answer
Most solar panels last 25 to 30 years or more. An NREL review of nearly 2,000 measurements found a median output loss of about 0.5% per year, so a panel typically still makes close to 90% of its original output after 20 years. Inverters usually need replacing once during that time, and Illinois' cool climate is easier on panels than hot climates.
How much output do solar panels lose over time?
NREL's review of decades of field data found a median degradation rate of about 0.5% per year, with higher rates in hotter climates and lower rates for many newer premium panels. For an 8.0 kW Chicago-area system, that looks like this:
| Year | Estimated production | Share of year 1 |
|---|---|---|
| 1 | 9,600 kWh | 100% |
| 5 | 9,410 kWh | 98% |
| 10 | 9,180 kWh | 96% |
| 15 | 8,950 kWh | 93% |
| 20 | 8,730 kWh | 91% |
| 25 | 8,510 kWh | 89% |
| 30 | 8,300 kWh | 86% |
Our savings calculator already includes this loss in its 25-year savings estimate.
Which solar parts need replacing, and when?
| Part | Typical life | Notes |
|---|---|---|
| Panels | 25–30+ years | Usually keep working past the performance warranty, at slightly lower output |
| String inverter | About 10–15 years | Plan on one replacement during the panels' life |
| Microinverters / optimizers | Often 20–25 years | Matched to long warranties; individual units can fail |
| Battery | About 10–15 years | Depends on how often it cycles |
| Racking and wiring | Life of the system | Inspect after major storms |
Does the Illinois climate shorten solar panel life?
Heat is the main driver of faster degradation, so Illinois' cooler temperatures help. Freeze-thaw cycles, snow loads and hail are the local stresses, and certified panels are tested for them. See solar in Illinois winters.
What happens to solar panels at the end of their life?
Many keep producing at reduced output well past 25 years, so homeowners often keep them running. When panels are removed, recycling options for glass, aluminum and silicon are growing; ask your installer how they handle removal and disposal.
Sources
This guide is general information, not tax, legal or financial advice. Incentive programs change, so confirm current terms with your installer, your utility and a tax professional.