How much does snow really cost you?
Snow on solar modules stops them producing. That sounds like a big problem in a city that can have snow on the ground from November to April. In practice it matters less than most people expect.
The reason is timing. Edmonton's winter months already produce only a small share of a system's yearly output, because the days are short and the sun is low. Losing some of that to snow cover is a modest dent in the annual total. The months that really count are April to September, when snow is rarely a factor.
Late-season storms are the exception worth knowing about. A heavy snowfall in April can cover panels at a time when they would otherwise be producing well. The good news is that spring sun is strong and temperatures are milder, so that snow rarely lasts more than a day or two on a tilted array.
Your system design already accounts for this. A good production estimate for an Edmonton roof includes expected snow losses. See how to size a home solar system.
Why panels usually clear themselves
Solar modules are smooth glass, dark and tilted, which is close to ideal for shedding snow. Even through a layer of snow, some light reaches the dark cells, which warm slightly. A thin film of water forms at the glass, and once enough of the sheet has loosened, it slides off, often all at once.
Several factors speed this up:
- Steeper tilt. Most Edmonton roof pitches work well. Very low-slope commercial roofs hold snow longer.
- Clear bottom edge. Snow slides more easily when nothing at the bottom of the array holds it back.
- Sun after the storm. A clear, cold day after a snowfall often clears the panels by afternoon.
- Ground mounts. Set steeply and high enough off the ground, they shed snow quickly and the snow has room to pile below.
The real hazard: where the snow lands
Because snow tends to release from modules as a sheet, it can come off the roof faster and all at once. That is a real safety issue if it lands on a front step, a walkway, a deck, a parked car or a gas meter.
Good design handles this before installation. The array layout can avoid the roof faces above entrances, or snow guards and deflectors can be added where people walk below. Gas meters and furnace or water heater vents need to stay clear of falling and piling snow; a buried vent is a carbon monoxide risk.
On the first warm, sunny days after a big snowfall, keep children and pets away from the eaves below solar arrays. Large sheets of snow and ice can come down without warning.
Should you clear snow off your panels?
For roof-mounted systems, the answer is no. The small amount of energy you would gain is not worth the risk of a fall from an icy roof. Clearing can also scratch the glass, damage the frames or void the warranty.
Avoid all of these:
- Climbing onto the roof in winter.
- Using a metal shovel, ice chipper or a stiff broom on the glass.
- Pouring hot water on modules. The temperature shock can crack the glass, and the water refreezes.
- Spraying de-icing chemicals that are not approved by the module manufacturer.
It is also worth knowing that the modules and the wiring behind them are energized whenever light reaches them, even through a little snow. Leave the rack, connectors and cables alone, and call your installer if you see damage after a storm.
If you have a ground-mounted array, a soft foam snow rake used gently from the ground is usually acceptable. Check your module manufacturer's guidance first, and leave it alone if there is a crust of ice.
Ice, eavestroughs and roof edges
Snow sliding off an array can pile up at the eaves and, with freeze-thaw cycles, contribute to ice build-up in eavestroughs. If you already have ice dams, solar will not fix them and may change where they form.
Keep an eye on where eavestroughs below the array discharge. Downspouts that dump meltwater across a walkway can create an icy patch right where sliding snow also lands. Redirecting the downspout is a simple fix that does not involve the solar system at all.
For roofs with persistent icing, self-regulating heat cable in the eavestroughs and downspouts is an option. See our roof and gutter de-icing service. It is designed and installed separately from the solar system and needs its own circuit.
Snow load and your roof
Your roof has to carry the weight of the modules and racking plus the snow that builds up on and around them. Racking also changes how snow drifts. For most houses this is checked as part of design, and older or modified roofs may need a closer structural look.
If you notice sagging, new cracks in interior ceilings or racking that has shifted after a heavy winter, call your installer. Our residential solar team can inspect the array and its connections.
A quick look from the ground each spring is a good habit. Check that the racking still looks straight, no modules have shifted, and no wiring is hanging loose under the array. Binoculars work well for this, and you never need to leave the ground to do it.
Common questions
Do solar panels work when covered in snow?
Not while fully covered. A thin layer may let a little light through, but most production stops until the snow slides or melts off, usually within a few days.
Should I buy a roof rake to clear my panels?
Not for roof-mounted systems. The risk of falls and damage outweighs the small winter production gain. Ground mounts can sometimes be cleared gently with a soft foam rake from the ground.
Will snow sliding off my panels damage anything?
It can, if it lands on a deck, car, gas meter or vent. Good array layout and snow guards in the right places prevent this.
Does snow reflect extra light onto panels?
Yes, bright snow on the ground can add a little reflected light, especially in spring. It helps most with steep ground mounts and panels that collect light on both sides.
Codes and permit rules change and every building is different. For work on your system, talk to a licensed electrician and your local permit authority.