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Home Backup Battery Size Equation:
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The Home Backup Battery Size calculation determines the required battery capacity (in amp-hours) needed to power your home for a specified duration during an outage, based on your power consumption and system voltage.
The calculator uses the following equation:
Where:
Explanation: The equation converts your power requirements into battery capacity by accounting for both the total energy needed (watt-hours) and the system voltage.
Details: Correct battery sizing ensures your backup system can meet your power needs without over-discharging batteries (which reduces lifespan) or being unnecessarily large and expensive.
Tips: Enter your total home power consumption in watts, desired backup time in hours, and system voltage. For accurate results, measure actual power consumption rather than estimating.
Q1: How do I determine my home's power consumption?
A: Use an energy monitor or check your electricity bill for average daily usage, then divide by 24 for hourly average. For critical loads only, sum the wattage of all devices you want to power.
Q2: What's the typical voltage for home battery systems?
A: Common voltages are 12V (small systems), 24V (medium), and 48V (large systems). Higher voltages reduce current and allow smaller wiring.
Q3: Should I add a safety margin to the calculated size?
A: Yes, it's recommended to add 20-30% to account for battery aging, inefficiencies, and unexpected load increases.
Q4: How does battery type affect the calculation?
A: Lead-acid batteries should only be discharged to 50% capacity, while lithium can often go to 80-90%. Multiply the result by 2 for lead-acid or 1.2 for lithium.
Q5: Can I use this for solar systems?
A: This calculates storage needs only. For solar, you'll also need to calculate how much solar input is required to recharge the batteries.