Off-Grid Calculator Suite — Solar ROI, Wire Gauge & Battery
Size off-grid power systems with three linked calculators: solar ROI, wire gauge for voltage drop, and battery runtime. All math runs in your browser. This free online tool runs entirely in your browser — no data is ever uploaded to a server. How to Use 1. Solar ROI — enter panel specs, sun hours, battery bank and cost to see payback math. 2. Wire Gauge — pick amp draw and run length to get the right gauge for low voltage drop. 3. Battery Runtime — size your load against the battery bank to get hours of autonomy. 4. Copy the numbers you need and plan your build — everything recalculates instantly. Example Enter 400 W of panels, 24 V / 100 Ah lithium bank and a 150 W average draw — the suite reports your energy margin, recommended wire gauge and roughly how long the battery lasts per day. Also check out the live tool at freeq.one/tools/offgrid — part of the FreeQ.One suite of free online tools.