Realistic days of autonomy for a family of four off-grid?

Battery Bank Sizing for Realistic Autonomy

When sizing a battery bank for a family of four, we need to consider their energy usage patterns. A general rule of thumb is to allocate 2-3 kWh per day per person. For a family of four, this translates to 8-12 kWh per day. To achieve 7-10 days of autonomy, we need to calculate the total battery capacity required.

Calculating Total Battery Capacity

To calculate the total battery capacity, we need to multiply the daily energy requirement by the number of autonomy days. For a 7-day autonomy, the total battery capacity would be 8-12 kWh/day * 7 days = 56-84 kWh. For a 10-day autonomy, the total battery capacity would be 8-12 kWh/day * 10 days = 80-120 kWh.

Real-World Battery Bank Sizing Example

Let’s consider a real-world example of a family of four with a moderate energy usage of 2.5 kWh per day per person. To achieve 7 days of autonomy, we would need a battery bank with a total capacity of 18.5 kWh (2.5 kWh/day * 7 days). To account for depth of discharge (DOD) and other inefficiencies, we would typically oversize the battery bank by 20-30%. In this case, we would need a battery bank with a capacity of 22-24 kWh.