Snow on Solar Panels & Panel Washing: The Real Story (2026)

Snow on panels — the math

Solar panels in snow country (MN, WI, ND, ME, NY, MI, MT, etc.) get covered for some number of days each winter. Reactive question: should I clear it?

The math:

• Annual production lost to snow cover: typically 1–5% of annual kWh, depending on climate. MN northern (Iron Range / Brainerd) ≈ 3–5%. Twin Cities / SE MN ≈ 1–3%. Winter sun is also lower in the sky, so even snow-free panels produce less — the marginal value of clearing is the difference between “snow-covered = 0%” and “clear = 30–50% of summer production.”
• What you'd recover by clearing: on a typical 8 kW system, recovering 4% of annual kWh = ~440 kWh = ~$60–$90 in MN at retail rate.
• What it costs to clear: if you do it yourself with a roof rake (Avalanche! Roof Snow Rake or similar), the rake costs ~$80 once, plus the time and risk. If you hire someone, expect $200–$400 per visit. Hiring an arborist with a fall-arrest harness is the only acceptable way to actually walk on the roof.
• Net: the math doesn't favor active clearing for most homeowners.

When clearing IS worth it

• Steep-pitch roofs that don't auto-shed. Most rooftop solar self-sheds within 1–3 days of sun warming. A 6/12 or steeper pitch sheds faster than a 4/12. Flat or low-pitch arrays can stay covered all winter — that's where active clearing helps.
• Ground mount with adjustable tilt. Some ground-mount frames let you tilt to 60–80 degrees in winter, dramatically improving shed.
• Income properties. If you're paid for production (Solar*Rewards, SREC, ConnectedSolutions battery dispatch), every kWh has value. Math shifts toward clearing.
• Off-grid systems. If snow-covered = no power, clearing matters far more than for grid-tied where you just buy from the grid until panels clear.

What NEVER to do

• Walk on snow-covered panels. Slippery, dangerous, can crack panels under your weight.
• Use a metal shovel or hard brush. Scratches the panel glass and may crack it.
• Use hot water. Thermal shock cracks the glass. Same risk in summer for very cold water on a hot panel.
• Use pressure washer. Pressure can void warranty AND drive water past panel-frame seals into the back-sheet.
• Use a roof rake aggressively. Light passes only. The Avalanche! brand rake has a polyethylene head specifically rated for solar — standard metal-edge roof rakes can scratch.

What CAN help (gently)

• From the ground with a long-handle telescoping pole + soft head: useful for low-mounted arrays. Sweep gently, top-down.
• Letting it shed naturally: 90% of the time the right answer.
• Heated panels (rare residential): Some manufacturers offer panels with integrated heating elements that can clear snow. Premium and rare.
• Tilting ground-mount panels: if your rack supports seasonal tilt adjustment, steeper winter angle sheds faster.

Panel washing — the math

Different question: do panels need washing in dry / dusty climates?

• Wet climates (PNW, NE, Midwest, Southeast): Rain washes panels naturally. Washing rarely improves production by more than 1–2%. Not worth the cost or risk.
• Dry climates (AZ, NM, west TX, inland CA, NV): Dust accumulates on panels because rain is rare. Annual washing can recover 5–10% production. Worth it if you can do it cheaply (garden hose + soft brush) or if you have a service contract.
• Bird droppings, pollen, pollen, smog: Localized soiling that benefits from a wash 1–2x per year in heavy areas.

How to wash panels (when it's worth it)

• Use water + soft brush, no soap. Manufacturer warranty often voids if soap residue causes streaking. If you must use a cleaner, use only a manufacturer-approved solution — or just plain water.
• Wash in early morning or evening. Cool panels avoid thermal shock from cold water on hot glass.
• Soft-bristle brush on a telescoping pole. Long handle keeps you off the roof.
• Garden hose, low pressure. Never use a power washer.
• Hire a window cleaner if you can't safely reach. Window-washing companies often offer panel washing as an add-on.

Soiling factors that matter most

• Pollen season — spring in deciduous areas; can build up enough to matter
• Forest fire smoke — ash deposits can drop production 5–10% during heavy fire seasons (CA, OR, WA, CO)
• Agricultural dust — near tilled fields, especially in growing season
• Bird droppings — localized but can drop a single panel's production significantly
• Coastal salt spray — less of an issue for panels themselves but can corrode aluminum frames over decades

Frequently asked questions