Solar Panels on a
Shipping Container Home

Load calculation is the foundation of system sizing — get this wrong and you'll either build an undersized system that leaves you in the dark or an oversized one that wastes money. Start by listing every device you'll run and its wattage, then estimate daily hours of use.

This table represents a modest single-person container home — similar to Ryan's setup. No air conditioning (the primary load that changes everything), no electric water heater, no electric cooking. Add any of those and your daily consumption can double or triple, requiring a much larger and more expensive system.

To find how many panels you need, divide your daily consumption by your location's average peak sun hours, then add a 25% buffer for inefficiency losses (wiring resistance, inverter conversion, temperature derating).

Formula: (Daily Wh ÷ peak sun hours) × 1.25 = minimum array wattage

For Ryan's build at ~2,000 Wh/day in the Ouachitas (5 peak sun hours): (2,000 ÷ 5) × 1.25 = 500W minimum array. In practice you'd size up — a 1,200–2,000W array gives headroom for cloudy days and future load additions.

Panel type: Monocrystalline panels are the right choice for container roofs — higher efficiency per square foot means you can fit more wattage in the limited roof area, and they perform better in the partial shade that edge objects and roof penetrations can create. Avoid polycrystalline for a space-constrained roof.

Your battery bank needs to cover your loads through the night and through cloudy periods — typically 1–3 days of autonomy for a well-designed off-grid system. The formula: (Daily Wh × autonomy days) ÷ depth of discharge = usable battery capacity needed.

For Ryan's 2,000 Wh/day with 2 days autonomy and 80% DoD on LiFePO4: (2,000 × 2) ÷ 0.80 = 5,000 Wh (5 kWh) usable capacity. A common configuration to achieve this is two 100Ah 48V LiFePO4 batteries (9.6 kWh total, 7.7 kWh usable at 80% DoD — giving comfortable headroom).

These two components sit between your panels/batteries and your loads. The charge controller manages power from the panels into the batteries. The inverter converts DC battery power to 120V AC for your outlets and appliances.

The corrugated steel container roof is strong enough to walk on and handle the panel load (typically 2–4 lbs/sq ft) without reinforcement. The main decisions are tilt angle, mounting method, and how to run conduit to the interior.

• Flat mount vs tilted: Flat mounting (0–5°) is simpler and lower-profile but loses some annual production. A tilt angle equal to your latitude (roughly 35° for Arkansas) maximizes annual output but adds wind load and height. For a container home, a low-tilt mount at 10–15° is a practical compromise — better production than flat, lower wind profile than optimal tilt.
• Mounting rails: Z-brackets or tilt-mount rail systems bolt through the roof with stainless steel hardware. Use EPDM washers under every penetration and seal with self-leveling silicone to prevent leaks. Run a bead of Dicor or similar on every roof penetration annually.
• Conduit run: Route DC wiring down the exterior wall in liquid-tight flexible conduit (LFMC) before entering the container through a weatherproof gland fitting. Keep DC runs as short as possible — longer runs mean voltage drop and thicker (more expensive) wire requirements.

Solar system wiring follows a standard sequence: panels → charge controller → battery bank → inverter → AC loads. DC wiring between components must be sized for the current at the system voltage — undersized wire is a fire hazard and a common DIY mistake.

The inverter output connects to a standard AC subpanel inside the container, which distributes power to outlets, lights, and fixed appliances exactly like a conventional residential electrical system. This is the part that most closely resembles conventional wiring.

• Subpanel: A small 60A or 100A subpanel inside the container receives 120V AC from the inverter and distributes it via standard breakers. Size the breakers to match each circuit's expected load.
• Wire before you insulate: All interior wiring should be roughed in before spray foam insulation is applied — conduit runs, outlet boxes, and light fixture boxes should all be in place first. You cannot add wiring after spray foam without cutting through it. See our complete container wiring guide for the full inside electrical walkthrough.
• Use NM-B (Romex) or conduit: Inside a spray-foam-insulated container, standard NM-B cable in a code-compliant installation is acceptable. In an uninsulated container or one with exposed steel, conduit (EMT or liquid-tight) is required.
• USB and 12V outlets: Consider wiring some outlets as direct 12V DC rather than routing through the inverter — this is more efficient for device charging and eliminates the conversion loss. USB-A/USB-C outlet panels mount in standard electrical boxes and run directly from the battery bank.