How many solar panels needed for a small off-grid cabin?

Load Calculation

To determine the required solar panel capacity, we need to calculate the cabin’s energy load. This involves identifying the daily energy needs of appliances such as lights, refrigerators, water pumps, and computers. A typical off-grid cabin may consume 20-50 kWh per day, depending on the usage. For this example, let’s assume a daily energy load of 30 kWh.

Panel and Battery Sizing

To size the solar panel system, we’ll use the daily energy load and the hours of sunlight the cabin receives. Assuming 5 hours of direct sunlight per day, we can calculate the required solar panel capacity. A 2-4 kW solar panel system would provide enough energy to cover the daily load. To choose the right panels, we’ll consider their wattage and efficiency. For this example, let’s select 320-watt panels with an efficiency of 19%. The required number of panels can be calculated by dividing the system capacity (2-4 kW) by the panel wattage (320 W). This yields 6-12 panels, but we’ll round up to 8-16 panels to account for system losses and future expansion.

Worksheet Example

To simplify the calculation process, we can use a solar panel sizing worksheet or a spreadsheet template. Here’s a simplified example:

• Daily energy load: 30 kWh
• System capacity: 2-4 kW
• Hours of sunlight: 5 hours
• Panel wattage: 320 W
• Panel efficiency: 19%
• Required number of panels: 8-16
• System losses: 10-20%
• Battery bank capacity: 12-24 kWh (deep cycle batteries, 12V)

We’ll use this worksheet to size the solar panel system, battery bank, and inverter. For this example, let’s assume a system capacity of 2.5 kW, 10 hours of battery backup, and a 12V battery bank with 192 Ah batteries. The required inverter capacity would be 2.5 kW, and the charge controller capacity would be 2.5 kW. This system design would provide a reliable and efficient energy supply for the off-grid cabin.