Daily power needs for an off-grid shed — how to calculate?

Identifying Essential Appliances

To accurately calculate daily power needs, start by listing the essential appliances and devices in the shed. Common items include LED lighting, refrigeration, power tools, and communication devices. For each item, determine the maximum daily energy consumption in watt-hours (Wh). For example, a 12V LED strip with 20 LEDs might consume 20-30 Wh per day, while a compact refrigeration unit could draw 30-50 Wh per hour, or 900-1500 Wh per day.

Calculating Daily Energy Consumption

Using the watt-hours per day for each appliance, add up the total daily energy consumption. A rough estimate for a basic off-grid shed might be: 10-20 Wh per day for lights, 30-50 Wh per day for a compact refrigeration unit, and 10-20 Wh per day for communication devices. With these values, the total daily energy consumption would be approximately 50-90 Wh per day. However, this amount only accounts for the appliances themselves and does not factor in system inefficiencies, such as battery charging losses and converter inefficiencies.

Buffering for System Inefficiencies

To account for system inefficiencies, add a 20-50% buffer to the total daily energy consumption. This ensures that the system can handle peak loads and still maintain a reserve of energy for emergencies. In the example above, the total daily energy consumption would be 60-135 Wh per day (50-90 Wh per day * 1.2 buffer). When selecting a battery and charging system for the off-grid shed, use this calculated daily energy consumption as a reference to ensure proper sizing and efficient operation.