Solar System Sizing Calculator

Calculate the optimal size for your solar power system

Key Formulas:
Daily Energy Requirement = Monthly Consumption (kWh) × 12 ÷ 365
Array Size (kW) = Daily Energy Requirement ÷ Average Sun Hours ÷ System Efficiency
Inverter Size (kW) = Array Size × 1.2 (20% oversizing)
Battery Capacity (Ah) = Daily Energy Requirement × Days of Autonomy ÷ Battery Voltage ÷ Depth of Discharge

Average Monthly Electricity Consumption (kWh):

Your Location: Select your location Southwest (6.5 sun hours/day) Southeast (5.0 sun hours/day) Northeast (4.0 sun hours/day) Midwest (4.5 sun hours/day) Northwest (3.8 sun hours/day) Custom (enter below)

Average Daily Sun Hours:

System Efficiency (%):

System Type: Grid-Tied (No Battery) Off-Grid (With Battery) Hybrid (Grid-Tied with Battery)

Battery Voltage (V): 12V 24V 48V

Days of Autonomy:

Depth of Discharge (%):

System Sizing Results

Daily Energy Requirement: 0 kWh

Array Size: 0 kW

Number of Panels (400W): 0 panels

Inverter Size: 0 kW

Battery Capacity: 0 Ah

Number of Batteries (100Ah): 0 batteries

Example Calculation

For a household with 900 kWh monthly consumption in the Southwest (6.5 sun hours/day), 80% system efficiency, grid-tied system:

Daily Energy Requirement = 900 kWh × 12 ÷ 365 = 29.6 kWh/day

Array Size = 29.6 kWh/day ÷ 6.5 hours/day ÷ 0.80 = 5.7 kW

Number of Panels (400W) = 5.7 kW ÷ 0.4 kW = 14.25 → 15 panels

Inverter Size = 5.7 kW × 1.2 = 6.8 kW → 7 kW

Recommended System: 6 kW array with 15 panels and 7 kW inverter

This calculator is part of "The Ultimate DIY Solar Power System: The Complete A-Z Guide"