Solar Panel Sizing Calculator
Solar Panel System Sizing
Calculate panels needed based on daily energy consumption
Battery Bank Sizing
Calculate battery bank size for off-grid solar
Formula
Panels = Daily kWh / (Sun Hours × Panel W × Loss Factor) | Battery Ah = (Daily kWh × Days) / (DoD × Voltage)
Frequently Asked Questions
How many solar panels do I need for my home?
Divide your daily kWh usage by the peak sun hours in your location, then account for system losses (typically 20%). Divide the required wattage by the panel wattage to get the number of panels. An average US home using 30 kWh/day with 5 peak sun hours needs about 7.5 kW, or 19 panels at 400W each.
What are peak sun hours?
Peak sun hours represent the equivalent number of hours per day when solar irradiance averages 1,000 W/m². This varies by location: 3-4 hours in northern states, 5-6 in the sunbelt, and 6-7 in desert areas. Check the NREL solar resource map for your location.
What system losses should I account for?
Typical system losses of 15-25% include: inverter efficiency (3-5%), wiring losses (2-3%), soiling/dirt (2-5%), temperature derating (5-10%), shading (0-10%), and panel degradation (0.5%/year). A 20% loss factor is a reasonable default.
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