Solar Panel Sizing Calculator

The standard photovoltaic sizing formula is: System Capacity (kW) = Daily Electricity Usage (kWh) / [Daily Peak Sun Hours * Solar System Derate Factor (typically 0.8)].

The derating factor accounts for real-world inefficiencies such as DC-to-AC conversion losses, inverter clipping, soil build-up, shading, and temperature degradation. A value of 0.8 is standard.

GCC cities like Riyadh and Dubai receive high daily averages of 5.8 to 6.2 peak sun hours, whereas US cities range from 3.5 peak sun hours in Northern states to 5.8 in Southern desert states like Arizona.

Battery Capacity (kWh) = [Daily Energy Usage (kWh) * Days of Autonomy] / Depth of Discharge (DoD). DoD is 0.8 for lithium-ion and 0.5 for lead-acid.

If utilizing standard 400-Watt solar panels, you will need 13 panels (5000 Watts / 400 Watts = 12.5, rounded up to 13).

Yes. Solar panels are rated at a Standard Test Condition (STC) of 25°C (77°F). Temperatures above this degrade the solar cells' voltage output, reducing efficiency by 0.3% to 0.5% per degree Celsius.

Daylight hours represent the entire duration from sunrise to sunset. Peak sun hours refer to the equivalent time during which solar irradiance reaches a constant 1,000 W/m².

An inverter is typically sized between 75% and 120% of the DC capacity of the solar array. For a 6 kW DC array, a 5 kW to 6 kW AC inverter is appropriate.

Size your battery capacity (in Amp-hours or kWh) to store enough energy to cover your critical daily household loads for a chosen number of buffer (autonomy) days, adjusting for chemical efficiency.

Depth of Discharge (DoD) is the percentage of a battery's capacity that has been discharged relative to its total capacity. Keeping batteries within recommended DoD levels prevents premature degradation.

Peak sun hours (1,000 W/m² solar intensity equivalent) range from 3.5 hours per day in northern regions to over 6.0 hours per day in sunny desert climates.

Daily kWh Output = Total Array Wattage (kW) × Peak Sun Hours × System Efficiency Factor (approx. 0.75 to 0.82).

Factor in a 15% to 25% combined system loss accounting for inverter conversion efficiency, wiring resistance, panel temperature derating, and dust/soiling.

Using standard 400-watt residential panels, a 10 kW system requires 25 panels (10,000W / 400W = 25).

Solar panels lose output efficiency as temperatures rise above 25°C (77°F), typically dropping by 0.35% to 0.45% per °C of temperature rise.

Off-grid arrays must be sized to generate 100% of daily energy needs plus extra power to recharge batteries, incorporating 2 to 3 days of autonomy reserve.

Modern 400W panels measure approx. 20 sq ft each. A 6 kW system (15 panels) requires approximately 300 sq ft of unshaded roof space.

Solar designs commonly use a 1.15 to 1.30 DC-to-AC ratio (oversizing panel capacity over inverter rating) to maximize morning and late afternoon energy harvesting.