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Solar cleaning, demystified.
Plain-English answers to the questions Wisconsin solar owners actually ask. Written by Marquis Mason, owner of Solar Alchemist.
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Shorter posts, seasonal reminders, and news from the roof.
Guides
June 28, 2026 · 5 min read
Why Rain Doesn't Clean Your Solar Panels in Wisconsin
What rain does and doesn't lift off Wisconsin solar panels, with NREL field data on annual soiling loss and how to spot buildup on your own glass.
Read articleJune 28, 2026 · 4 min read
What the Wisconsin State Capitol Job Taught Me About Solar Panel Soiling
A 17-year-old rooftop array. One brand-matched cleaning. 16.7% more sunlight reaching the glass — a same-panel spot reading, not a system-wide production claim.
Read articleJune 28, 2026 · 5 min read
Solar Panel Cleaning and Your Warranty: What You Need to Know
Most warranty-voiding cleaning mistakes are silent. This guide walks through the cleaning methods every major panel manufacturer publishes and exactly which techniques preserve your coverage.
Read articleFebruary 14, 2026 · 4 min read
Your New Solar Array's First Wisconsin Pollen Season
If your rooftop system was installed in the last twelve months, spring 2026 is the first pollen season it will face. What to watch for, when to act, and why your production guarantee may already require you to.
Read articleFebruary 14, 2026 · 5 min read
July 4, 2026 Deadline: What Your New Commercial Array Needs Before Spring 2027
The federal commercial-solar tax-credit deadline pushed a wave of construction starts into 2026. Spring 2027 is the first full pollen season those arrays will face, and production guarantees may already require documented cleaning.
Read articleSources & Citations
Every factual claim on the site is anchored to a public source. Grouped below by topic so procurement, insurance, and homeowner audits can verify quickly.
Production Loss & Soiling Research
Where my soiling-loss language comes from, the NREL PV Fleet report and how I frame ranges honestly rather than promising a percentage.
- NREL, Soiling Losses Quantitative Study (2024), National Renewable Energy Laboratory. Annual soiling losses across U.S. PV fleets, median ~5%, with regional variation up to 15%+.
- NREL, Addressing Soiling on PV Modules, NREL Research Hub. Field methodology and cleaning-recovery measurements across multiple climates.
- IEA-PVPS, Soiling Losses Impact on PV Performance, International Energy Agency, PV Power Systems Programme. Agricultural soiling rates regularly exceeding 15% annually without intervention.
- Princeton, Regular Panel Cleaning & Air Quality (2021), Princeton Environment in the Half Century. Regular cleaning + air-quality improvements raise PV output, especially in high-pollution / low-rain regions.
Rain Cannot Clean Pollen
Why I tell visitors that rain alone is not enough, backed by NREL field research.
- NREL, Rain Not Enough to Wash Pollen from Solar Panels (2023), NREL News Program. Direct NREL release stating rain alone is insufficient to remove pollen, requiring scheduled cleaning.
- Renewable Energy World, NREL Pollen Study Summary, Renewable Energy World. Independent reporting on the 2023 NREL pollen findings: >15% peak losses during pollen season.
Hot-Spot & Permanent Damage
Peer-reviewed evidence that bird streaks, pollen, and localized soiling do not just reduce output, they create hot-spots that permanently degrade the underlying cells and cut usable panel life.
- Energies (MDPI, 2024), Electrothermal Modeling of PV Modules for Hot-Spot Detection Caused by Soiling, Energies, 17(19), 4878. Directly connects soiling to hot-spot formation via thermal-imaging detection and electrothermal modelling.
- Rossi et al., Modeling and Detection of Hotspot in Shaded Photovoltaic Cells, IEEE Transactions on VLSI Systems. Names bird droppings and tree leaves as shading sources that trigger hot-spotting and can "produce permanent damage of the shaded cell, with a consequent reduction of the provided power."
- Dhimish et al. (2017), Output-Power Enhancement for Hot Spotted Polycrystalline PV Solar Cells, IEEE Transactions on Device and Materials Reliability. Establishes that hot-spot heat can damage the cell encapsulant and cause "second breakdown", permanent damage rather than temporary output loss.
- Olalla et al. (2018), Mitigation of Hot-Spots in PV Systems Using Distributed Power Electronics, Energies, 11(3), 726. Quantified figure: hot-spot-induced permanent damage can cause a lifetime energy loss above 15%.
Wisconsin State Capitol Solar Array
Verification of my most-cited customer outcome, the 2009 installation I cleaned in 2026.
- Renew Wisconsin, Solar Panels Rise to Capitol Heights, Renew Wisconsin. Confirms install date (2009), 48-panel count, ~9,600 sq ft installation, MGE-owned. The 16.7% more-sunlight-at-the-glass figure is my own measured before/after irradiance reading on a single tested panel on cleaning day — not a system-wide production claim. See /our-work for the irradiance readings and full disclosure.
Insurance, Warranty & Wear-and-Tear
Why a paper trail of professional cleanings protects your homeowner / commercial policy and warranty.
- Insurance Information Institute, HO-3 Sample Policy (PDF), III.org. Standard HO-3 form explicitly excludes wear-and-tear, deterioration, and neglect, insurers use this exact policy language.
- NAIC, Homeowners Insurance Topics, National Association of Insurance Commissioners. Industry-level confirmation of policy-form prevalence and exclusions.
- Solar Insure, Gaps in a Solar Production Guarantee, SolarInsure.com. Installer production guarantees typically require documented cleaning/maintenance before honoring an underperformance claim, separate from the manufacturer panel warranty.
Cleaning Method, Brushes & Deionized Water
Why I use pole-fed deionized water and brand-matched contact tooling, backed by manufacturer documentation.
- LG Solar, Official Cleaning Guidance, LG.com. LG officially recommends deionized water + non-abrasive brush; advises against tap water, abrasives, and cleaning agents.
- Enphase, Solar Panel Cleaning Guide, Enphase Energy. Industry-standard soft-brush / gentle-rinse protocol.
Local Wisconsin & Electric-Rate Data
Why I use $0.16/kWh and warn about hard-water mineral deposits in the Madison area.
- U.S. EIA, Wisconsin Residential Electricity Profile, U.S. Energy Information Administration. Wisconsin residential average ~$0.16/kWh (used in the $80–$250/yr soiling-loss math on-site).
- Madison Metropolitan Sewerage District, Water Hardness, madsewer.org. Confirms hard water in the Madison area, the mineral source for the white spotting I remove with deionized rinse.
- NREL, PV Degradation Rates Review (1,900-system meta-study), NREL. Median panel degradation of ~0.5%/year (used to distinguish slow degradation from sudden soiling losses).
- Alliant Energy, Wisconsin Rate Review, AlliantEnergy.com. PSC-approved settlement raising Wisconsin electric rates roughly 3.5% in 2026 and 6% in 2027, meaning every kWh lost to soiling costs more each year.
- Solar Insure, Commercial Solar Tax-Credit Deadline (July 4, 2026), SolarInsure.com. Federal commercial tax-credit construction-start deadline of July 4, 2026 drove a wave of 2026 commercial installs whose first full pollen season is spring 2027.