Sun Sizer Pro app icon WORKS 100% OFFLINE

Survey the site.
Size the system.

A complete solar design toolkit for iPhone and iPad: string sizing, wiring and code checks, sun path, production and off-grid sizing. Everything works right on the roof, with no signal needed.

Coming soon to the App Store See what's inside
14-day free trialiPhone & iPadiCloud syncNo sign-upNASA climate data built in
Site & Sun tools: sun path, measure tilt, shade, roof plane, row spacing, area to panels Sun path arc with the best fixed tilt for the site Estimated annual production of about 13,000 kWh

Every calculation, one app

Five toolsets that share one project, so you enter the numbers once.

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Array

  • String sizing: min & max panels per string from cold Voc and hot Vmp
  • Inverter match: DC:AC ratio, MPPT and combiner checks
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Wiring

  • Voltage drop over the run
  • Ampacity & OCPD (NEC 690.8)
  • Battery cables & fuses
  • Conduit run and working-space clearance
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Site & Sun

  • Sun path & best seasonal tilt
  • Measure tilt & azimuth with the device's sensors
  • Shade, row spacing and area → panel count
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Energy

  • Production & ROI with 25-year payback
  • Off-grid sizing: loads, battery, array and inverter surge
  • MPPT / PWM charge controller checks
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Workflow

  • Projects with a live code-check summary
  • Reusable panel, inverter and battery library
  • iCloud sync across iPhone & iPad
  • Client-ready PDF reports
Sun Sizer Pro on iPad showing a panel layout mockup

Built for iPad, too.

With the tools in a sidebar and your results side by side, the big screen is great for design reviews at the kitchen table or on the tailgate.

  • Live layout mockups: portrait vs landscape
  • Code checks flagged the moment an input changes
  • Every calculator reads from and writes to the active project

Made for the field

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No signal? No problem.

Climate data and every calculation are on the device, so it works on rural sites, rooftops and in basements. Changes sync to your other devices when you’re back online.

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Private by design

No sign-up, no ads, no tracking. Projects sync only through your own private iCloud, and we never see them.

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Shows its work

Results cite the check behind them, such as cold-weather Voc per NEC 690.7, so you can verify every number.

Try every tool free for 14 days

No charge and nothing renews. After the trial, String Sizing and Sun Path & Tilt stay free and your projects stay viewable. Unlock everything for good with a one-time Premium purchase. It’s not a subscription.

Results are design estimates. Always verify against equipment datasheets, the NEC edition your area has adopted, and your local AHJ before installation.