Emergency Backup Power for Off-Grid Homes — How to Prepare?

Assessing Critical Loads

To ensure emergency backup power, it’s essential to identify and calculate the wattage requirements of critical loads in your off-grid home, such as lights, refrigeration, and medical equipment. Use a worksheet to estimate the total load, considering both AC and DC devices. A general rule of thumb is to prioritize essential loads, such as refrigeration and lighting, which consume around 50-100 watts each. For a typical off-grid home, the total load might range from 500 to 2,000 watts.

Sizing the Battery Bank

The battery bank should be sized to cover a minimum of 1-2 days of autonomy for critical loads, taking into account factors like load reduction, solar charging, and battery depth of discharge. A common approach is to use a 50% depth of discharge (DOD) for lead-acid batteries and a 30% DOD for lithium-ion batteries. For example, a 1,000 watt load might require a 4-8 kWh battery bank, depending on the DOD and charging profile.

Inverter/Charger Selection

Choose an inverter/charger with a high surge capacity to ensure it can handle the startup current of critical loads. A typical surge capacity range is 2-5 times the inverter’s continuous output power. For example, a 2,000 watt inverter with a 4,000 watt surge capacity can handle the startup current of a refrigerator or air conditioner. When selecting an inverter/charger, also consider its efficiency, charging algorithm, and remote monitoring capabilities to ensure optimal performance and monitoring.