Quick Answer
Prioritize battery backup for critical loads in your home, such as lighting, refrigerator, and medical equipment, to ensure a reliable power supply during outages. Consider loads that are essential for comfort and safety. Allocate capacity accordingly to meet your household's needs.
Selecting Critical Loads
When prioritizing critical loads for battery backup, consider the National Electric Code (NEC) definition of essential systems: “essential systems” include “medical equipment, refrigeration units, and lighting.” Allocate 2-3 kWh of battery capacity to support medical equipment, such as ventilators or dialysis machines, to ensure continuous operation during outages. For refrigeration units, allocate 1-2 kWh to maintain temperatures below 40°F (4°C) for perishable food and medication.
Load Calculations and Capacity Allocation
To determine capacity allocation for other loads, calculate the power consumption of each load in watts and multiply by the desired backup duration in hours. For example, a 100-watt refrigerator consuming power for 2 hours requires 200 Wh (100W x 2h) of battery capacity. Allocate 20-30% of total capacity to support lighting loads, which typically range from 100-500 watts. For comfort loads, such as air conditioning and heating, allocate 30-50% of total capacity, depending on your household’s needs and regional climate.
Automatic Transfer Switches and Load Control
To ensure seamless transition between grid and battery power, install an automatic transfer switch (ATS) and load control system. The ATS detects grid power loss and automatically switches to battery power, while the load control system manages load shedding during low battery levels. Configure load control to shed non-essential loads, such as air conditioning and water heaters, while preserving critical loads like medical equipment and refrigeration units.
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