Understanding winter-only cabin sizing
The direct answer for a typical winter cabin
A cabin using 2,200Wh a day with 3 winter peak sun hours needs about 980 watts of panel and roughly 674Ah of battery with cold derate applied. This is a notably larger system than the same load would need in a milder season, since both lower sun hours and reduced battery capacity from cold work against the system at the same time. The NREL's PVWatts calculator lays out the same rules from the regulator's side. Your inverter has to handle the biggest load you will run at once. The quick inverter size estimator in our Inverters & Equipment section can help you size it for your actual appliances.
Why cold derate is mandatory, not optional, for this use case
Other cabin sizing tools treat cold weather derate as an optional adjustment for occasional cold snaps within a broader multi-season use pattern. A winter-only cabin doesn't have that luxury: every single time the cabin is occupied, the battery is operating in cold conditions, so building the derate in as a default rather than an afterthought reflects how the system will actually perform every time it's used. The federal ITC calculator picks up where this leaves off, using the figure you just found.
Snow cover and panel tilt
Snow accumulation on panels temporarily blocks production entirely until it slides off or melts. A steep panel tilt, 50 to 70 degrees from horizontal, helps snow shed faster than the shallower angles used in summer-only installs, and also happens to better capture the naturally low winter sun angle. Dark panel surfaces often self-clear once any direct sun hits them, since the panel warms and melts the snow's underside, but a steep mount speeds this process considerably. The panel tilt for winter sun calculator fine-tunes that mounting angle for your specific latitude. The Department of Energy's homeowner's guide to going solar lays out the same rules from the regulator's side.
Hunting cabins versus ski cabins
Both fall under winter-only use, but their loads differ enormously. A hunting cabin often runs a minimal load of lighting, a radio or satellite communicator, and maybe a small heater, while a ski cabin with running water, a furnace fan, and multiple occupants running electronics needs a substantially larger system. Run your actual load list through this tool rather than assuming one winter cabin's sizing applies to another, and if you're at a particularly high latitude on top of winter-only use, the northern latitude winter sizing tool compounds both effects together.
What to check once you have a system size
The temperature side of winter output loss is handled separately by the temperature derate calculator in our performance and output tools, worth running alongside this one since cold affects panels and batteries differently. Winter seasonal production swings, the same ones behind NREL's PVWatts calculator, are the underlying data this tool's sun-hour estimates draw from. A winter-only build still qualifies for the same federal tax treatment as a year-round system, covered by the federal ITC calculator in our rebates and incentives tools, and the Department of Energy's homeowner's guide to going solar lays out the general planning framework from there.