Off-Grid & Solar Sizing
Off-Grid & Solar Sizing calculators — each with the formula, a worked example and a reference table. Results are estimates for planning and education; verify all sizing with a licensed electrician and your AHJ.
Off-Grid System Size
Enter your daily energy use in watt-hours, your peak sun hours, system voltage, days of au…Solar Panel Size
Enter your daily energy in watt-hours, your peak sun hours, a system derate factor and the…Battery Bank
Enter your daily energy in watt-hours, the days of autonomy you want, your system voltage …Inverter Size
Enter the total running watts of everything you would power at once and the largest single…Charge Controller
Enter your solar array watts, the battery voltage and the controller type to find the char…Watt-Hours
Enter a battery voltage and its amp-hour rating to convert to watt-hours and kilowatt-hour…Series / Parallel
Enter one cell or battery voltage and amp-hours, plus how many you wire in series and in p…Panel Output
Enter your solar array size in kilowatts, your peak sun hours and a system derate to estim…Off-grid sizing starts from one number: daily watt-hours
Designing an off-grid or solar system is a chain of calculations that all begin with your daily energy use in watt-hours — the sum of every load's wattage times the hours it runs. Get that number with the Watt-Hours calculator, then the rest follows. The Off-Grid System Size calculator turns daily watt-hours into the array and battery targets; the Solar Panel Size calculator divides the energy you need by the peak sun hours for your location to give the array wattage, because a panel only makes its rated power under full sun for a limited part of the day.
Storage is sized by the Battery Bank calculator from three inputs: how much energy you use, how many days of autonomy you want for cloudy stretches, and the usable depth of discharge of your chemistry (lithium tolerates far deeper cycling than lead-acid). The Inverter Size calculator matches the inverter to your largest simultaneous AC load plus motor surge, and the Charge Controller calculator sizes the controller and helps you choose between MPPT and PWM. Wiring the array itself is a trade-off the Series / Parallel calculator makes explicit: series strings add voltage, parallel strings add current, and the combination sets the controller's input window. Verify a panel's real-world yield with the Panel Output calculator.
For the reasoning behind the numbers, see how to size an off-grid solar system, battery-bank sizing explained and MPPT vs PWM charge controllers. For year-round off-grid reliability, size against the worst solar month, not the annual average. These are planning estimates; confirm final component and wire sizing against the NEC and a qualified installer.