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Backup System Calculation:
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A solar panel battery backup system stores excess energy generated by solar panels for use when the panels aren't producing enough electricity (like at night or during power outages). The system's capacity determines how long your essential loads can run on stored energy.
The calculator uses the simple formula:
Where:
Explanation: This calculation gives you the minimum battery storage capacity (in kWh) needed to support your solar system for the desired backup duration.
Details: Proper sizing of your battery backup system ensures you have enough stored energy to meet your needs during power outages or when solar production is low, while avoiding overspending on unnecessarily large battery systems.
Tips: Enter your solar panel system size in kW and the number of backup hours you desire. For more accurate results, consider your actual energy usage patterns and efficiency losses (typically 10-15%).
Q1: Is this calculation exact?
A: This provides a basic estimate. Real-world factors like battery efficiency (typically 85-95%), depth of discharge limits, and temperature effects should be considered for precise sizing.
Q2: How many batteries do I need?
A: Divide the total kWh by your battery's capacity. For example, 10 kWh backup with 5 kWh batteries would require 2 batteries (plus any needed for efficiency losses).
Q3: What's a typical backup duration?
A: Most residential systems are designed for 8-24 hours of backup for essential loads. Critical systems may need longer durations.
Q4: Can I expand my system later?
A: Many battery systems are modular, allowing you to add capacity later. Check with your installer about expansion options.
Q5: How long do solar batteries last?
A: Most modern lithium-ion batteries last 10-15 years or 5,000-10,000 cycles, depending on usage patterns and depth of discharge.