Solar Panel Maintenance: The Complete Annual Checklist (What to Check and When)

Solar panels are low-maintenance by design — no moving parts, sealed units, 25-year warranties. But "low maintenance" is not the same as "zero maintenance."

A properly maintained system runs at full rated output for its entire 25-year life. A neglected system loses 0.5–1% of output per year to preventable causes — adding up to 10–15% reduced lifetime generation.

Here's exactly what to check, how often, and what to do when something is wrong.

Ongoing Monitoring (Monthly)

The single most valuable maintenance habit is checking your inverter output data monthly. Every modern inverter — Enphase, SolarEdge, Fronius, GoodWe — has a monitoring app or web dashboard that shows daily, monthly, and annual generation in kWh.

What to look for:

• Compare year-on-year: A 5%+ unexplained drop in generation for the same month compared to previous years indicates a problem. Normal panel degradation is 0.5% per year — anything beyond that needs investigation.
• Compare sunny day output: Note what your system produces on a clear sunny day in each season. If a similar day produces noticeably less, something has changed.
• Look for panel-level anomalies (microinverter systems): Enphase and other microinverter monitoring shows per-panel output. A panel producing significantly less than its neighbours indicates shading, soiling, or a failed cell.
• Check for error codes: Most inverter apps flag faults with error codes. A grid fault, ground fault, or overtemperature error should be investigated promptly — some indicate a safety issue.

Set a calendar reminder on the same day each month to check your monitoring app. This takes 2 minutes and is the single most effective maintenance habit for catching problems early.

Cleaning Schedule

Cleaning frequency depends entirely on your location and local conditions:

For the cleaning method, materials, and what cleaners are safe to use, see the full solar panel cleaning guide → with the Simple Green method that works safely from the ground.

For the full analysis of when rain does and doesn't do the cleaning work for you, see does rain clean solar panels? →

Annual Visual Inspection (From the Ground)

Once per year, spend 15–20 minutes doing a careful visual inspection of your panels from the ground using binoculars if necessary. Look for:

Panel surface

• Visible soiling, bird droppings, or debris — clean if present
• Discolouration, yellowing, or browning of cells — indicates EVA delamination or cell degradation
• Cracks in the glass surface — any crack should be reported to your installer immediately
• Hot spots — visible as dark patches on the panel surface; often caused by cell damage or partial shading. A thermal camera (some smartphones have this feature, or hire an inspector) can identify these definitively
• Snail trails — brown branching marks across cell surfaces, caused by micro-cracks. A warranty claim issue if visible.

Mounting and racking

• Check that all panels are still sitting flat and correctly positioned — no panel should be lifting at a corner or showing movement
• Look for any corrosion on metal mounting rails or clamps, particularly in coastal environments
• Check that cable management (conduit runs, clips, any visible wiring) is still intact and not damaged by UV, animals, or wind movement

Roof around the panels

• Check for any signs of water ingress around penetration points — staining, bubbling paint, or damp patches on the ceiling below after rain
• Look for any lifted or cracked roof tiles adjacent to the array that may have been disturbed during installation

Inverter Checks

Your inverter is the only moving part in your solar system (the fan inside) and the component most likely to need attention before the panels do. Typical inverter lifespan is 10–15 years — shorter than the 25-year panel warranty, meaning most systems will need an inverter replacement during their lifetime.

What to check annually:

• No error lights or fault codes on the inverter display or app
• Inverter ventilation slots are clear of dust and debris — restricted airflow causes overheating and reduced efficiency
• The inverter location is not excessively hot — inverters installed in lofts or enclosed hot spaces run hotter and degrade faster; an unshaded, ventilated location is ideal
• No unusual sounds (rattling, buzzing) from the inverter when running

If your inverter is 10+ years old: Get a professional check of the capacitors and DC disconnect. These are the most common failure points in ageing inverters.

When to Call a Professional

Call your installer or a qualified solar technician for any of the following:

• Persistent inverter error codes that don't clear after a restart
• Ground fault errors — these can indicate a serious wiring issue and should not be ignored
• Output has dropped 10%+ compared to previous year on equivalent days and cleaning doesn't recover it
• Visible cracks in panel glass
• Any signs of roof water ingress near the array
• Scorch marks, burning smell, or discolouration around inverter, junction boxes, or wiring
• Your inverter is 12+ years old and hasn't been professionally serviced

Most reputable installers offer annual maintenance contracts — typically £80–£150/year (UK) or $100–$200/year (US) — which include a professional inspection, cleaning, and inverter check. Worth considering if you're not comfortable doing the visual inspection yourself or if your system is on a steep roof.

Solar Panel Lifespan and Degradation

Solar panels degrade slowly over time — this is normal and factored into the economics of solar. The industry standard degradation rate is approximately 0.5% per year for monocrystalline panels. At this rate:

• Year 10: ~95% of original output
• Year 25: ~87.5% of original output
• Year 30: ~85% of original output

Most panel manufacturers guarantee 80% of rated output at year 25 (the production warranty). If your panels fall below 80% before year 25, you have a warranty claim.

Degradation above 0.5%/year can be caused by: PID (Potential Induced Degradation) from poor earthing, hot spot formation from cell damage, and EVA delamination from poor quality manufacturing. All of these show up in monitoring data as accelerated output decline — another reason why monthly monitoring is the most valuable maintenance habit.

Frequently Asked Questions

How much maintenance do solar panels need?

Very little. The main tasks are: checking inverter monitoring data monthly (2 minutes), cleaning 1–4 times per year depending on climate, and a 20-minute annual visual inspection from the ground. Total annual time commitment is typically 2–4 hours for a homeowner doing it themselves.

Do solar panels need servicing?

The panels themselves rarely need professional servicing within their 25-year warranty period. The inverter typically needs professional attention at 10–12 years old and replacement at 12–15 years. A professional inspection every 3–5 years is good practice to catch issues not visible from the ground.

What reduces solar panel lifespan?

The main factors are: physical damage (hail, falling debris, vandalism), PID from poor earthing, sustained high operating temperatures from poor ventilation or very hot climates, manufacturing defects, and salt air corrosion in coastal locations. Regular cleaning, good installation quality, and monitoring all help maximise lifespan.

How do I know if my solar panels are working correctly?

Check your inverter monitoring app monthly and compare output on similar sunny days year-over-year. An unexplained drop of 5%+ on equivalent days indicates a problem worth investigating. For microinverter systems, per-panel monitoring shows immediately if a single panel is underperforming. For string inverter systems, a clamp meter check of DC string current by a professional can identify failed panels.