How Many Solar Panels Do I Need for a Cabin? A Practical Off‑Grid Guide
Going off‑grid is one of the most rewarding decisions you can make — but figuring out how many solar panels your cabin actually needs can feel overwhelming. The good news: once you break it down into the right variables, the math becomes straightforward. This guide walks through the essentials and shows what real‑world setups look like for small, medium, and large cabins.
What Determines Your Solar Panel Count?
No two cabins are the same, so there's no universal number. Four factors drive your system size:
1. Your Daily Energy Consumption
Start by listing the appliances you use and how long they run each day. A few common examples:
- LED lighting (10 bulbs, 5 hrs): ~0.5 kWh/day
- Refrigerator: ~1.5 kWh/day
- Laptop: ~0.1 kWh/day
- Water pump: ~0.3 kWh/day
- Electric tankless water heater: ~2–4 kWh/day
Add it up — that total is your daily kWh target.
2. Peak Sun Hours
Solar panels only produce full output during "peak sun hours," typically 4–6 hours per day depending on your region and season.
- Southwest: 5–6 hours
- Pacific Northwest: 3–4 hours in winter
Use a solar map or NREL's PVWatts tool to find your local average.
3. Panel Wattage
Modern high‑efficiency panels — like 590W N‑Type bifacial modules — produce far more power per panel than older 250W–300W models. Higher wattage means fewer panels for the same output, which is critical when roof or ground space is limited.
4. System Losses
Real‑world systems lose 15–25% of generated power to heat, wiring, inverter conversion, and battery charging. A 20% buffer is the standard for accurate sizing.
The Simple Solar Sizing Formula
Number of panels = Daily kWh ÷ Peak sun hours ÷ Panel wattage (kW) × 1.25
Example:
Daily use: 5 kWh
Peak sun: 5 hours
Panel: 590W (0.59 kW)
5 ÷ 5 ÷ 0.59 × 1.25 ≈ 2.1 panels
Round up to 3 panels for a comfortable margin.
Recommended Setups by Cabin Size
Small Cabin (weekend retreat, minimal loads)
- Daily usage: 2–4 kWh
- Recommended: 2–4 × 590W panels
- Battery storage: 5–10 kWh
- Supports: lighting, phone charging, small fridge, water pump
Medium Cabin (part‑time or seasonal living)
- Daily usage: 5–10 kWh
- Recommended: 4–8 × 590W panels
- Battery storage: 10–20 kWh
- Supports: full kitchen appliances, entertainment, low‑demand tankless water heater
Large Cabin (full‑time off‑grid living)
- Daily usage: 10–20+ kWh
- Recommended: 10–20 × 590W panels
- Battery storage: 20–40 kWh
- Supports: HVAC, full kitchen, multiple occupants, home office
Don't Forget Battery Storage
Solar panels generate power during the day — batteries carry you through nights and cloudy weather. A common rule of thumb is 1–2 days of storage.
Example: A medium cabin using 8 kWh/day should have 16–24 kWh of battery capacity.
LiFePO₄ batteries are the standard for off‑grid systems:
- Safer
- Longer lifespan (3,000–5,000 cycles)
- Better deep‑discharge performance
A Note on Water Heating
Hot water is one of the biggest energy loads in any cabin. Electric tankless heaters can dramatically increase your daily kWh requirement. Switching to a propane or natural gas tankless water heater removes that load from your solar system entirely — reducing panel count and protecting your battery bank from heavy spikes.
It's a combination many off‑grid homeowners rely on.
Ready to Size Your System?
The best off‑grid solar setups are built around your actual lifestyle — not a generic estimate. Track your energy use for a week, identify your biggest loads, and size your system from there.
At Miles Off Grid, we carry high‑efficiency solar panels, power systems, and off‑grid essentials to help you build a setup that works for your cabin — not just on paper.
