Off-Grid System Sizer

Block inspector

Click a block to edit its parameters, or drag from a port to wire it into the system.

Sizing & equipment spec

About the method

Solar resource is estimated per‑site from latitude and day‑of‑year sun geometry, scaled by a clearness index for the chosen climate class (with a wet/dry‑season swing for tropical sites). Wind resource is a rough estimate from a chosen exposure class — it varies far more with local terrain than solar does, so replace it with measured data whenever you have it. Both are fully editable per month on the Location block. This runs entirely in your browser: nothing is sent anywhere, and it doesn't call live weather APIs.

Panel, battery, inverter and charge‑controller sizing follow the standard off‑grid method (peak‑sun‑hours for the array; nameplate = Wh/day × autonomy ÷ (DoD × efficiency) for the battery, sized against the worst month's load, not the annual average; inverter matched to peak simultaneous demand with surge headroom; controller current oversized for safety). Battery capacity is also reported in Ah at the bus's DC system voltage for procurement specs.

The performance banner runs a full 8760‑hour simulation: the array's monthly daily total is spread across each day by the sun's actual path, the load by the chosen 24‑hour shape, and the battery is charged and discharged hour by hour between 100% and its discharge floor. Charge and discharge each lose the battery's efficiency factor (so round‑trip is that factor squared). Simplifications worth knowing: wind is held steady at each month's mean speed, there is no battery charge‑rate (C‑rate) limit, the generator simply follows the load up to its rating rather than bulk‑charging the bank, and sky variability is synthetic rather than a real weather year — so treat "battery empty" as a design indicator, not a guarantee.

System performance 8760‑hour simulation