PV System Sizing & Design: Complete Step-by-Step Methodology

The Six-Step Design Process

Load Assessment: Audit all appliances, their wattage, and daily runtime. Calculate total daily energy (kWh/day).
Array Sizing: Array power (kWp) = Daily Energy ÷ (Peak Sun Hours × System Efficiency). Account for seasonal worst month.
Battery Sizing: Battery capacity (kWh) = Daily Energy × Autonomy Days ÷ (DoD × Efficiency).
Charge Controller Sizing: Controller current (A) = Array Power (W) × Safety Factor ÷ System Voltage (V).
Inverter Selection: Continuous rating ≥ peak load. Surge rating ≥ motor starting loads. Match DC input voltage.
Cabling & Protection: Size cables for ≤3% voltage drop. Select appropriate breakers, fuses, and disconnects.

Daily load: 8 kWh. Location: 5.2 PSH. System voltage: 48V. Autonomy: 3 days. LiFePO4 battery, 80% DoD.

Array = 8,000 ÷ (5.2 × 0.75) = 2,051 W → 2.5 kWp array. Battery = 8,000 × 3 ÷ (0.8 × 0.95) = 31,579 Wh → 32 kWh (≈ 660 Ah @ 48V).

Load Assessment: Audit all appliances, their wattage, and daily runtime. Calculate total daily energy (kWh/day).
Array Sizing: Array power (kWp) = Daily Energy ÷ (Peak Sun Hours × System Efficiency). Account for seasonal worst month.
Battery Sizing: Battery capacity (kWh) = Daily Energy × Autonomy Days ÷ (DoD × Efficiency).
Charge Controller Sizing: Controller current (A) = Array Power (W) × Safety Factor ÷ System Voltage (V).
Inverter Selection: Continuous rating ≥ peak load. Surge rating ≥ motor starting loads. Match DC input voltage.
Cabling & Protection: Size cables for ≤3% voltage drop. Select appropriate breakers, fuses, and disconnects.

Daily load: 8 kWh. Location: 5.2 PSH. System voltage: 48V. Autonomy: 3 days. LiFePO4 battery, 80% DoD.

Array = 8,000 ÷ (5.2 × 0.75) = 2,051 W → 2.5 kWp array. Battery = 8,000 × 3 ÷ (0.8 × 0.95) = 31,579 Wh → 32 kWh (≈ 660 Ah @ 48V).