Daily kWh needs for a remote cabin — how to calculate?

Calculating Appliance Power Consumption

To accurately estimate daily kWh needs, list all appliances and devices that will be used in the cabin. Then, determine their power consumption in watts (W). For example, a small LED light bulb uses about 9 W, while a 12V refrigerator uses around 20-40 W. Multiply the power consumption by the number of hours the device is used per day to find the daily kWh needs. For instance, a 9 W light bulb used 8 hours a day would consume 0.072 kWh (9 W x 8 h).

Estimating Peak Demand

Peak demand occurs when multiple devices are used simultaneously, requiring a larger amount of power. To estimate peak demand, consider the appliances that will be used simultaneously during the evening hours when power is typically needed the most. For example, if a cabin has a refrigerator, lights, and laptop, and they are all used at the same time, calculate the combined power consumption: 20 W (refrigerator) + 9 W (light) + 65 W (laptop) = 94 W. Convert the combined power consumption to kWh by multiplying by the number of hours they are used per day, then add a 10-20% buffer to account for the inefficiencies in the solar panel system.

Sizing Solar Panel Systems

When sizing solar panel systems, consider the total daily kWh needs, peak demand, and the cabin’s available roof space. A general rule of thumb is to oversize the system by 10-20% to account for any inefficiencies or unexpected power usage. For example, if the cabin needs 2.5 kWh per day, calculate the required solar panel system size: 2.5 kWh / 0.5 (peak sun hours per day in the region) = 5 kW. Then, oversize the system by 10-20% to ensure adequate power generation.