How Many Solar Panels Do You Need to Power a Cabin

"How many panels?" is one of the most-asked cabin solar questions, and the honest answer requires understanding what you actually use. This guide walks through the sizing calculation without oversimplifying to a fixed number.

The three inputs that determine panel count

1. Daily energy use (Wh/day). How much electricity your cabin actually consumes across a typical day. This is the driver of everything else.

2. Sun hours at your location. "Peak sun hours" is a standardized measure of how much sunlight a panel receives on a typical day. Northern locations get fewer hours; southern locations get more. Winter values are much lower than summer.

3. Battery capacity and desired autonomy. How many cloudy days should the system ride through before running out. Larger battery bank plus larger panel array = more autonomy.

Estimating daily energy use

Start with your specific loads:

Total these for your specific use case. A typical weekend cabin might land at 500-1,500Wh/day. A full-time cabin with well pump and fridge might land at 2,000-4,000Wh/day.

Sun hours by location

Peak sun hours vary dramatically by location and season:

• Southern US in summer: 5-6 peak sun hours/day
• Southern US in winter: 3-4 peak sun hours/day
• Northern US in summer: 4-5 peak sun hours/day
• Northern US in winter: 2-3 peak sun hours/day

Cabin design should size for the worst month you actually plan to use the cabin. If you never visit in December, don't size for December sun. If the cabin runs year-round, worst-month sizing matters a lot.

The sizing calculation

Panel wattage needed ≈ (Daily energy use in Wh) ÷ (Peak sun hours per day) × (System loss factor)

System loss factor is typically 1.3-1.5 (accounts for battery charge inefficiency, wiring losses, weather variability). For quick estimates, use 1.4.

Example: Weekend cabin, 1,000Wh/day, northern US summer (4.5 sun hours):
1,000 ÷ 4.5 × 1.4 = 311W of panels. Round up to 400W (two 200W panels).

Example: Full-time cabin, 2,500Wh/day, mid-latitude winter (3 sun hours):
2,500 ÷ 3 × 1.4 = 1,167W of panels. Round up to 1,200-1,600W depending on cloudy-day margin desired.

The autonomy factor

Cabin systems should be sized for more than just average daily production. Multi-day cloudy stretches drain the battery bank; larger panel arrays recover faster once sun returns.

Rule of thumb: for cabins with generator backup, moderate margin (10-20% over calculated) is enough. For cabins without generator, generous margin (50-100% over calculated) plus a large battery bank prevents multi-day cloudy outages.

Panel selection: fewer larger vs. more smaller

Modern 400W monocrystalline panels are the mainstream cabin choice. Three 400W panels total 1,200W in less space than four or five 300W panels totaling the same wattage. Larger panels:

• Fewer connections (fewer failure points)
• Less mounting hardware
• Better cost per watt at wattage class
• Bigger, harder to move and install alone

Smaller panels (100-200W):

• Easier to install alone
• More flexible mounting options
• Redundancy if one panel fails
• Higher cost per watt at low wattage class

For most cabin builds, 200-400W panels hit the sweet spot.

Growing the array over time

Cabin solar systems often grow over years as loads and expectations increase. Design the initial charge controller and wiring to support the future array size, not just the current array size. It's much easier to add panels than to swap out an undersized controller.

Typical growth path:

1. Start with 400-800W for basic loads (lights, phones, small fridge).
2. Add a second string (400-800W more) when adding well pump or larger fridge.
3. Add more panels for high-consumption loads (Starlink, larger appliances, EV charging).

Panel orientation and tilt

Panels should face south (in the northern hemisphere) at a tilt roughly equal to your latitude. For cabin-optimized winter performance, tilt to latitude + 15° (steeper); for summer optimization, latitude - 15° (flatter). For year-round balance, use latitude.

Ground mount is more flexible for cabin installations than roof mount — you can optimize angle for the season and the panels are accessible for cleaning and snow removal.

Reality-check the math with real cabin data

The above math gives a starting point. Verify with cabin owners in similar climates and use profiles. Real experience data — "I have a 1,000W array and a 400Ah LiFePO4 bank, and it just barely handles my full-time cabin with well pump in winter" — is more valuable than pure calculation.

Solar sizing calculators online can produce more sophisticated estimates but shouldn't substitute for either the math or the community wisdom.

Bottom line

For a typical weekend cabin, 400-800W of panels usually works. For a full-time cabin with well pump and fridge, 1,200-2,400W is realistic. Calculate your actual daily energy use, adjust for your worst-month sun hours and desired autonomy, and add margin for cloudy days. Design controller and wiring for future growth. This is one of those sizing questions that reward careful thinking upfront — cabin solar systems that get sized right work for decades with minimal issues.