Solar Panel & Battery Storage Sizing Calculator
Size solar photovoltaic array (kW DC), 400W panel counts, roof area, and LiFePO4 battery storage capacity based on daily kWh consumption and sun hours.
Solar Insolation & Load Parameters
NREL PVWatts • NEC 690/706Net metering interconnection, structural roof engineering & permits.
About This Calculator & Field Methodology
Engineering sizing engine for grid-tied, hybrid, and off-grid solar energy systems. Formulated using NREL PVWatts solar insolation methodologies and NEC Article 690 & 706 standards. Calculates necessary DC array wattage, required Tier-1 solar panel quantities, estimated roof area, and battery storage capacity (usable kWh vs nameplate kWh) with selectable days of autonomy.
Standard formulas derived from international trade engineering standards (NEC Table 310.16, ACCA Manual J 8th Ed, ACI Concrete Mix Manual). Actual physical installations may require local authority having jurisdiction (AHJ) approval.
ToolHub Renewable Energy Group
Solar PV Systems Designer & NABCEP Professional · NABCEP PV Installation Professional & IEEE Member
Strict compliance with NEC, ACCA, and ACI code standards.
Frequently Asked Questions
Q:How do Peak Sun Hours differ from total daylight hours?
Peak Sun Hours (PSH) represent the equivalent number of hours per day when solar irradiance averages 1,000 Watts per square meter (1 kW/m²). While a summer day may have 14 hours of daylight, the solar intensity morning and evening is low; typical regions in the US receive between 3.8 and 6.2 Peak Sun Hours daily.
Q:What Depth of Discharge (DoD) should I calculate for home batteries?
Modern Lithium Iron Phosphate (LiFePO4) solar batteries typically have a safe Depth of Discharge (DoD) of 90% to 100%, allowing almost all stored energy to be used without shortening cell lifespan. Older Lead-Acid or AGM batteries should only be discharged to 50% DoD to prevent rapid degradation, requiring double the nameplate capacity.
Q:How many solar panels are needed to power an average American home?
The average US single-family home consumes roughly 890 to 950 kWh per month (~30 kWh/day). In a region with 4.5 Peak Sun Hours, this requires an 8.0 to 8.5 kW DC solar system, which equates to approximately 20 to 22 standard 400-Watt solar panels occupying roughly 430 to 470 square feet of unshaded roof.
Q:How large of a battery is needed to run a refrigerator and essentials during a blackout?
A modern Energy Star refrigerator consumes roughly 1.2 to 1.8 kWh per 24 hours. For critical loads including a refrigerator, LED lighting, Wi-Fi router, and phones (approx. 5 to 7 kWh/day), a single 10 kWh to 13.5 kWh home battery (such as an Enphase 10T or Tesla Powerwall) comfortably provides 24 to 36 hours of continuous backup.
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