Sun Sizer

Sun Sizer Pro is a solar design toolkit for installers, DIY builders and off-grid homesteaders. Size the array, check the wiring, measure the site and hand the client a clean PDF — all on your phone, even with no signal on the roof.

Everything runs on the device. No account, no cloud, no ads, and nothing you enter ever leaves your phone.

DESIGN THE ARRAY • String Sizing — minimum and maximum panels per string from your coldest and hottest site temperatures, checked against the inverter's voltage window. • Inverter Match — DC:AC ratio, current per MPPT input and combiner checks. • Area → Panels — enter roof length, width and fire setbacks and see a to-scale layout of how many panels fit, in portrait or landscape. • Row Spacing — shade-free row pitch for a 9 am–3 pm window on the shortest day, now including sloped ground.

WIRE IT SAFELY • Voltage Drop — AWG or mm², copper or aluminum, AC or DC. • Ampacity & OCPD — NEC-style conductor sizing with temperature and conduit-fill derating, and the breaker to match. • Battery Cables & Fuses — DC cable size, fuse rating and interrupt rating for battery banks.

READ THE SITE • Sun Path & Tilt — a watch-face dial of the sun's path for any day, sunrise and sunset, and the best tilt for year-round, summer or winter production. • Measure Tilt & Azimuth — lay the phone on a panel to read its angle and the direction it faces, with roof pitch in twelfths. • Shade & Obstructions — mark a tree or chimney with the camera to get its height and see exactly when it shades the array. • Roof & Ground Plane — capture a roof's tilt, facing and size with the camera. • Built-in NASA climate data for most of the world, so production estimates use real monthly sunlight and temperatures for the site.

ESTIMATE THE PAYBACK • Production & ROI — monthly and annual kWh, savings and payback, shown as an honest range rather than a single hopeful number. • Over the system's life — panel degradation, rising electricity prices and an optional inverter replacement, with lifetime output and cost per kWh. • Off-Grid Sizing — appliance loads, days of autonomy, battery bank, worst-month array size and inverter surge. • Charge Controller — MPPT or PWM sizing with cold-weather voltage checks.

ON THE JOB • Conduit & Cable Run — walk the route with the camera and send the length straight to Voltage Drop. • Working Space — check the clearance in front of an inverter or panelboard against NEC 110.26. • Projects — enter the site and equipment once and every calculator uses them. Duplicate a project to compare two designs. • PDF reports — share a clear report with code checks, estimates and assumptions. • Equipment library — save your panels, inverters and batteries, and share whole projects with a colleague by AirDrop.

BUILT FOR THE FIELD • Works completely offline. • Imperial or metric units. • A high-contrast sunlight mode for bright days on the roof. • Designed for iPhone and iPad.

Camera measuring is sharpest on iPhone Pro and iPad Pro models with LiDAR, and every camera tool also accepts typed measurements.

FREE AND PREMIUM String Sizing and Sun Path & Tilt are free. A one-time Premium purchase unlocks every other tool — no subscription.

Sun Sizer Pro is a design aid. Always confirm your results against the equipment manufacturer's specifications and your local electrical code before installing.

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