Understanding full-time cabin sizing
The direct answer for a typical full-time cabin
A cabin using 2,800Wh a day with 2.8 winter peak sun hours needs about 1,250 watts of panel and roughly 437Ah of battery for 3 days of autonomy. This is a meaningfully larger system than a weekend or seasonal cabin, reflecting both a heavier typical daily load and the requirement to fully cover the worst month without any recharge gap to lean on. The federal ITC calculator is the natural follow-up once this part is settled.
Why worst-month sizing is not optional for full-time living
A seasonal or weekend cabin can undersize its winter production somewhat, since the empty weeks between visits give panels extra time to recharge the battery even on a low-production day. A full-time cabin has no such gap: every day is a day the system needs to keep up with load, so sizing around the annual average instead of the worst month risks running short every winter, not just occasionally. This is the single biggest sizing mistake in full-time off-grid builds. The Department of Energy's homeowner's guide to going solar keeps the current program details, and it is worth a look before you decide.
Why a generator backup is close to mandatory
Even a system correctly sized for the worst average month can fall short during an unusually long or severe cloudy stretch, since "worst month" is an average, not a guaranteed floor. Rather than oversizing the battery bank to cover a rare multi-week event, most full-time off-grid builds pair solar with a generator backup sized to cover the gap on the rare occasions it's needed, which is far more cost-effective than an extremely large battery bank sitting mostly unused. Remote systems are easy to neglect. The panel lifespan estimator in our Maintenance & Lifespan section can help you budget for the maintenance that keeps output from slipping.
Why higher voltage often makes sense
Full-time cabins commonly run larger loads than seasonal builds, and higher system voltage, 24V or 48V instead of 12V, delivers the same power at lower current, which reduces wiring losses and the wire gauge needed throughout the system. The 12V vs 24V vs 48V comparison covers this trade-off for larger systems in more depth. Real household consumption patterns, the kind EIA tracks in its residential energy survey, are a useful cross-check against whatever daily load figure you've plugged into this tool. Even off-grid, the money side matters. The levelized cost of energy calculator in our Savings & Payback section can help you compare the system cost with the cost of extending the grid.
What to check once you have a system size
With a wattage target and a battery size in hand, run the northern latitude winter sizing tool if you're in a consistently cold, low-sun climate. If your household is a different size than what you sized here, the system size by household size tool in our system sizing tools scales the same underlying math to your specific headcount. Before buying, it's worth checking the federal ITC calculator in our rebates and incentives tools, since a full-time off-grid build often qualifies the same way a grid-tied system would; the Department of Energy's homeowner's guide to going solar covers the planning steps that come after the tax-credit math.