soft-26-solar-battery-sizing-guide-2026.md

Why Sizing a Solar Battery Correctly Matters More Than Anything Else

A solar battery system that is undersized will leave you without power. One that is oversized costs significantly more than necessary. Getting the sizing right — based on real data, not rules of thumb — is the single most important step in any solar project specification.

Step 1: Define Your Daily Energy Requirement

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List every load in the system. For each load, multiply power draw (watts) by hours of use per day.

Example — small commercial solar system (resort in the Philippines):

• Lighting (LED, 20 fixtures × 10W × 8 hours): 1,600Wh/day
• Air conditioning (1,500W × 6 hours): 9,000Wh/day
• Refrigeration (200W × 24 hours): 4,800Wh/day
• Wi-Fi and security (100W × 24 hours): 2,400Wh/day
• Total: 17,800Wh/day ≈ 18kWh/day

This is the minimum energy the battery must supply during periods without solar generation.

Step 2: Determine Required Days of Autonomy

Autonomy = number of cloudy days the battery must bridge without solar input.

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