Off-grid by project · Cabins
Off-grid cabin solar: how to size panels, batteries and an inverter
A cabin can run on solar for a weekend or all year. The difference is how much you use, when you use it, and how dark your winters get.
At a glance
Two example cabins
These use typical values from the appliance wattage chart, 400 W panels, and the same sizing math as the off-grid planner.
Weekend cabin: 2.86 kWh a day
Fridge, lights, phones, a laptop and a well pump; propane for heat, cooking and hot water.
| Season | 400 W panels | Battery (2 days) | Battery (3 days) |
|---|---|---|---|
| 5 sun hours (summer) | 3 (1.2 kW) | 8.57 kWh | 12.88 kWh |
| 2.5 sun hours (winter) | 5 (2.0 kW) | 8.57 kWh | 12.88 kWh |
Inverter: the loads likely to run at the same time total 1,275 W, so plan about 1,594 W continuous and 3,275 W surge so the well pump can start while everything else runs. The washer and coffee maker are left out because you can run them at other times.
Full-time cabin: 5.75 kWh a day
Adds a chest freezer, internet, TV, washer, microwave and coffee maker.
| Season | 400 W panels | Battery (2 days) | Battery (3 days) |
|---|---|---|---|
| 5 sun hours (summer) | 5 (2.0 kW) | 17.25 kWh | 25.87 kWh |
| 2.5 sun hours (winter) | 9 (3.6 kW) | 17.25 kWh | 25.87 kWh |
Inverter: the loads likely to run at the same time total 3,000 W, so plan about 3,750 W continuous and 5,000 W surge so the well pump can start while everything else runs. The washer and coffee maker are left out because you can run them at other times.
Size your own cabin system
- Daily use
- 2.86 kWh
- Battery (2 days)
- 8.57 kWh
- Inverter
- 1,594 W
- Startup surge
- 3,275 W
Uses the same math as the off-grid planner at 4 peak sun hours. A planning estimate, not a design.
The calculator's inverter figure assumes every selected load runs at once. Size the real inverter from what runs together, as in the examples above.
How a cabin system fits together
- Ground-mount arrayTilted for winter, clear of shade
- Charge controllerOften built into the inverter
- 24V or 48V batteryIndoors, above freezing
- Inverter/chargerGenerator plugs in here
- Cabin panel and loadsWired by an electrician
A generator connects to the inverter/charger as a backup input. Fuses or breakers sit between the array and controller and between the battery and inverter.
Ground mount or roof?
- Ground mounts are easier to tilt steeply for winter, clear of snow, and reach for cleaning. They're the usual choice for cabins with open land.
- Roof mounts save space but need a structural check, proper flashing, and safe access. Shade from trees is the most common problem at cabins.
- Distance matters. A long run from the array to the cabin wastes power in the wire. Wiring panels in series raises the voltage and cuts loss, but strings above about 50V DC need proper isolation and a review. See what's safe to DIY.
Use the right energy for each job
- Heat: wood stove or propane heater. A propane furnace's blower still uses electricity; it's in the calculator.
- Cooking and hot water: propane range and tankless or tank water heater.
- Refrigeration: an efficient electric fridge or chest freezer on solar is usually simpler than propane fridges.
- Water: a well pump has a big startup surge, so the inverter must handle it. See inverter sizing.
Plan for winter and time away
- Size for your darkest month. A cabin used in December needs far more panels than a summer-only one. See off-grid solar in winter.
- Protect the battery when you leave. Lithium batteries shouldn't be charged below about 32°F (0°C). Use low-temperature charge protection or self-heating, and switch off loads you don't need while you're away.
- Keep a generator. It covers long storms for far less than extra panels and batteries.
- Consider remote monitoring. Many charge controllers and battery monitors report over Wi-Fi or cellular, so you can check the system before you drive up.
Permits and professional help
Plug-in systems and power stations rarely need a permit. Once solar is wired into the cabin's panel, most counties require a permit and inspection, and that wiring is a job for a licensed electrician. Plan the system yourself, then have a professional review it before you buy. The DIY vs. professional guide breaks down who does what.
FAQ
How many solar panels does an off-grid cabin need?
A weekend cabin with a fridge, lights and a well pump uses about 2.86 kWh a day, which is roughly 3 × 400 W panels in summer. A full-time cabin can need 9 or more in winter. Size for the darkest month you plan to use it.
What size battery does a cabin need?
Plan two to three days of storage for cloudy weather. That's often 8–13 kWh for a weekend cabin and 17–26 kWh for full-time use, with a generator covering longer storms.
Should my cabin system be 12V, 24V or 48V?
Most cabins do best at 24V or 48V. Higher voltage keeps battery current and cable size down, and many all-in-one inverter/chargers for cabins are 48V.
Can I run heat on solar at a cabin?
Electric resistance heat is rarely practical off-grid. Use wood or propane for heat, cooking and hot water, and save solar for the fridge, lights, pump and electronics.
Do I need a permit for an off-grid cabin solar system?
Usually, if it's wired into the cabin. Most jurisdictions require a permit for a fixed electrical installation even when it isn't grid-connected. Check with your county building department.