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Solar Panel Sizing Calculator

Calculate required solar panel array wattage and panel count based on daily energy consumption and peak sun hours.

1. Enter your numbers  →  2. Check the answer  →  3. Read the steps before you trust it

Wh

e.g. 3.6 kWh/day = 3600 Wh

hours/day

Typical US/Europe: 3.5 - 5.5 hours

%

Accounts for temp, dust, inverter loss (typically 75-82%)

Recommended Photovoltaic Array

Recommended Array Capacity
1,000 W (1 kW)

Consisting of approx 3 × 400W panels

Estimated Number of Panels
3 Panels
Daily Energy Target
3,600 Wh/day

Step-by-Step Engineering Calculation

  1. 1Daily Energy Requirement: Edaily=3600 Wh/dayE_{\text{daily}} = 3600\text{ Wh/day} (3.60 kWh/day3.60\text{ kWh/day})
  2. 2Solar Production Factor: 4.5 PSH×80% Efficiency=3.60 effective full-sun hours4.5\text{ PSH} \times 80\%\text{ Efficiency} = 3.60\text{ effective full-sun hours}
  3. 3Required Solar Array Capacity: Parray=3600 Wh3.60 hrs=1000.0 WP_{\text{array}} = \frac{3600\text{ Wh}}{3.60\text{ hrs}} = \mathbf{1000.0\text{ W}} (1.00 kW1.00\text{ kW})
  4. 4Estimated Panel Count (400W panels): ⌈1000.0 W400 W⌉=3 panels\lceil \frac{1000.0\text{ W}}{400\text{ W}} \rceil = \mathbf{3\text{ panels}} (Total nominal capacity: 1200 W)

Formula & Theory

Array Watts = Daily Energy (Wh) / (Peak Sun Hours × System Efficiency)

Determines photovoltaic array sizing needed to replenish daily kilowatt-hour consumption.

Variable Definitions
E_daily:
Daily Energy (Watt-hours (Wh)) – Daily electrical energy consumption
PSH:
Peak Sun Hours (Hours (h/day)) – Equivalent solar insolation at 1000 W/m²
η_sys:
System Efficiency (Percentage (%)) – Overall derate factor (typically 75-82%)

Worked Engineering Example

Off-Grid Cabin Solar Array

Consuming 3,600 Wh/day in a region with 4.5 Peak Sun Hours and 80% system efficiency.

Inputs:
  • Daily Energy: 3600 Wh
  • Peak Sun Hours: 4.5 h
  • Efficiency: 80%
  • Panel Rating: 400 W
Result: Required Array = 1,000 W (3 × 400W Panels, 1,200W total)

Key Assumptions

  • •Standard panel orientation, tilt angle, and unobstructed southern exposure.

Limitations & Safety Scope

  • •Winter insolation is substantially lower than summer; off-grid systems should size for worst-month solar averages.

Frequently Asked Questions

What are Peak Sun Hours?

A Peak Sun Hour represents one hour during which solar irradiance averages 1,000 Watts per square meter (1 kW/m²).

Related Calculators & Engineering Tools

Battery Capacity Calculator
Inverter Size Calculator
Energy Cost Calculator
Solar Battery Bank Sizing Guide
How to Size a Power Inverter

Educational & Reference Notice: This calculator provides technical estimates based on standard physical formulas. Actual electrical installation, protective device sizing, and conductor selection must be verified against the applicable electrical code (NEC, IEC, CEC) by a licensed electrician or qualified professional engineer.