For cabins, RVs and full off-grid homes with no utility backup. Sized for worst-case sun, not the annual average.
This sizes energy, not appliance surge — run the exact figure through the Inverter Size Calculator once you know your equipment.
Further reading: Off-Grid Solar 101: What It Actually Takes to Leave the Grid
A grid-tied system can undersize slightly, because the grid fills any gap. Off-grid can't — so it's sized against your worst realistic sun day, not the annual average, and paired with enough battery to coast through a multi-day cloudy stretch without a generator. Whether you search for a solar off grid calculator or an off grid solar calculator, this is the same worst-case-sun-hours approach behind both.
Whether you call it an off-grid solar power system design calculator, an off-grid solar system sizing calculator, or simply an off-grid solar system simulator, the underlying design process is the same four-step sequence this tool runs through: (1) total your daily load in kWh across every appliance and circuit that has to run without the grid; (2) divide that by your worst-case sun hours to get the array size; (3) multiply daily usage by your target autonomy days for usable battery kWh, then divide by depth-of-discharge for the battery's rated capacity; (4) size the inverter and charge controller to the array and battery, not just the load. Simulating a few different autonomy-day and DoD combinations here is exactly how you'd stress-test an off-grid design before buying hardware.
Most off-grid systems keep a small generator for the rare multi-day low-sun stretch beyond their autonomy design — it's cheaper than oversizing the battery bank for a once-a-year event.
Yes, if you choose an inverter/charge controller rated for your eventual array size upfront — expanding panels later is easy, replacing the inverter is not.
The battery-sizing math shown here (usage × autonomy ÷ depth-of-discharge) is the core of any off-grid battery calculator — for a dedicated battery-only view with chemistry-specific depth-of-discharge presets, see the Battery Size Calculator.
Both — an off-grid solar panel calculator on its own would only size the array, but going fully off grid means the panel count, battery bank, inverter and charge controller all have to be sized together as one off grid solar system calculator, which is what this tool does in a single pass.
They're the same thing in practice — "simulator" just emphasizes running multiple what-if scenarios (different autonomy days, panel counts, or usage levels) rather than a single one-shot calculation, which is exactly what changing the inputs above lets you do.