Snow on solar panels: why the honest answer is usually to leave it

How much power does snow cost a Macomb County array?

Less than a covered roof suggests. Two numbers from the National Renewable Energy Laboratory, renamed the National Laboratory of the Rockies in late 2025, frame it:

• Winter is a small share of the year. In NREL's PVWatts calculator, with its default settings, a 6-kilowatt array facing south at a 25-degree tilt in Macomb Township makes about 4 percent of its yearly output in December, January about 5 and February about 7: roughly 16 percent for the three snowiest months combined, before any snow loss. June and July each make nearly three times what December does.
• Snow takes only part of that. NREL's 2017 national study, built on a snow model that Marion and colleagues developed from measured systems in Colorado and Wisconsin in 2013, estimated average annual snow losses for a Detroit array at 5.6 percent with a 20-degree tilt and 4.5 percent with the tilt set equal to the latitude. The highest in the lower 48 were close to 16 percent, in northern Minnesota, with Sault Ste. Marie at about 15.

On the PVWatts array, which makes about 7,900 kilowatt-hours a year, 5 percent is roughly 400 kilowatt-hours over a whole winter. That is about the most that clearing after every single storm could win back, and it would mean going up after every snowfall.

Why do solar panels shed snow on their own?

Tilted glass is slick. NREL's snow model treats sliding as the main way snow leaves an array, with how much slides depending on the tilt, the sunlight and the air temperature. In the NREL study, the steeper Detroit array lost less to snow than the flatter one. Sharp's installation manual puts it plainly: snow slides more easily off the smooth surface of a module than off the rest of the roof.

Why not scrape the snow off?

Three reasons, in order of how badly each can go:

1. The fall. A roof-mounted array means standing on, or reaching up to, a snowy roof. The Qcells installation manual warns of the risk of falling and says to hire a trade specialist for cleaning. It also warns of injury from live modules.
2. The glass and its coating. Qcells says to remove snow and ice carefully and without force, with something like a very soft broom, and not to scratch off dirt. It lists scratched glass, a damaged anti-reflective coating and power loss among the results of the wrong cleaning.
3. The warranty. Qcells says damage caused by cleaning, or by the tools or agents used, is not covered by its product and performance warranty. Read your own panel maker's terms before anyone touches the array.

Stick to what the manufacturer allows. Qcells' example is a very soft broom; a metal roof rake, an ice scraper and a kettle of hot water are all outside that guidance.

What about ground-mounted arrays?

A ground array within reach is the one case where light clearing can make sense, done the manufacturer's way:

• Use only a very soft tool your panel maker allows, pushed down the slope of the glass, and leave the last film to slide or melt.
• Keep the low edge open. SunPower's snow model, presented at Sandia's PV Performance Modeling Collaborative, assumes snow slides off a module only if there is room below the array for it to collect. When the pile under the low edge reaches the panels, the snow has nowhere to go. Shoveling that pile away lets the array clear itself.
• Knock down overhangs. Sharp's manual says overhanging snow and ice on the module frame can deform it and should be removed periodically.
• Tell your snow company where it is. A ground array near the driveway belongs on your stop notes, so the crew does not push snow toward it or pile it against the low edge. Mark it, too: see driveway markers.

What about snow sliding off the panels?

That is the real winter hazard. Sharp's manual warns that snow on modules may suddenly slide off the roof and hit nearby objects or areas, and it recommends snow stoppers where that could cause injury or damage.

• Look at what is under the low edge of each array: the front walk, the steps, a deck, the spot where a car parks.
• If people walk there, ask your installer about snow guards made for your array and roof.
• Until then, keep people and cars out of the landing zone on sunny or mild days after a snow, when sliding is most likely.
• Snow that lands on a deck adds load in one strip; see snow and ice on decks. For the roof itself, see roof snow load warning signs.