Every figure our solar calculator produces is derived from established engineering formulas and industry-standard data sources. Here's exactly how it works.
We sum this across all selected appliances to get your total daily load. This is the foundational figure every other calculation depends on.
We use 5.0 peak sun hours as the global default — this represents a median across most inhabited regions worldwide (ranges from 3.5 in Northern Europe to 6.5 in Middle East/Africa). System efficiency is set to 80% to account for real-world losses including heat, wiring, and inverter conversion.
Source: NREL (National Renewable Energy Laboratory) — Global Solar Resource Data
We round up to the nearest whole number since you cannot install fractional panels. The default panel wattage is 550W — the current industry-standard monocrystalline module size for residential and commercial installations.
A 20% safety headroom prevents inverter overloading during peak generation hours. We snap to commercial inverter sizes: 1.5, 2, 3, 3.6, 4, 5, 6, 8, 10, 12, 15, 20 kW.
Source: IEC 62109 — Safety for Power Converters Used in Photovoltaic Power Systems
Depth of Discharge (DoD) varies by chemistry: Lithium-Ion = 85% (industry standard for LFP batteries), Lead-Acid = 50% (manufacturer recommendation to preserve cycle life). For lead-acid in 48V systems, we enforce series multiples of 4 (each 12V battery × 4 = 48V). For 24V systems, multiples of 2.
Source: IEC 62619 — Safety Requirements for Secondary Lithium Cells and Batteries
Used for the 5.0 peak sun hours global default and regional validation.
Inverter sizing methodology and safety headroom guidelines.
Depth of discharge and safety parameters for lithium battery banks.