Solar System Sizer

Our free Solar System Sizer helps off-grid homeowners, RV solar installers, and remote cabin builders accurately size their complete solar power system — from battery bank to panel array to charge controller. The intuitive appliance load builder lets you add any device with its wattage and daily usage hours. Total daily watt-hours are automatically summed to determine your energy budget. Battery bank sizing accounts for autonomy days (cloudy day backup) and depth of discharge limits for your chosen chemistry, giving results in both watt-hours and amp-hours at 12V for easy component selection. Panel array sizing adds a 1.25 safety factor over your daily load divided by peak sun hours, ensuring reliable recharging under real conditions. The charge controller recommendation includes a further 25% current headroom over the calculated panel array amps, matching NEC 690 wiring standards for solar installations. This browser-based off-grid solar calculator requires no registration and processes all data locally for complete privacy. It is used by DIY solar enthusiasts, professional installers, and engineering students worldwide. Start with the five pre-loaded default appliances — fridge, lights, TV, phone charging, and a water pump — or clear the list and build your own. The tool covers all common system voltages from 12V small systems to 24V and 48V larger installations. Understanding the relationship between your load, battery bank, panel array, and charge controller is fundamental to building a reliable off-grid solar system that won't leave you in the dark during extended cloudy periods. This free sizing tool provides a solid engineering starting point for any off-grid solar project, large or small.

This tool is part of our collection of 100+ free online utilities designed to help developers, designers, and professionals work more efficiently. All tools are completely free, require no registration, and process data locally in your browser for maximum privacy and security. We continuously update and improve our tools based on user feedback to ensure they meet the evolving needs of our global community. Whether you're working on personal projects, professional tasks, or educational assignments, our tools provide reliable solutions that respect your privacy and deliver instant results. The intuitive interface makes it easy for beginners to get started while providing advanced features for experienced users. All tools include comprehensive documentation, example data, and helpful tips to ensure you get the most out of every utility. We believe in making powerful tools accessible to everyone, regardless of technical expertise or budget constraints.