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Solar Sizer support
Off-grid solar planning calculator
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Common questions
Where do I get peak sun hours?
Look up your location in NREL PVWatts or the NSRDB viewer (links are in the app), then type the number in. A lower winter figure gives a safer off-grid size.
A result looks too big or too small.
Check three things first: hours per day for each appliance, peak sun hours, and battery depth of discharge. Most surprises come from one of those.
Why does the charge controller use 125%?
The National Electrical Code treats solar current as continuous, so equipment is sized at 125% of it. It is a starting point; your installer and local code have the final say.
Where is my data?
Only on this phone. More → Export backup saves a JSON file of your plan and saved systems; Import backup brings it back. You can also export saved systems as CSV.
Does it cost anything?
Version 1.0 is free, with no ads and no purchases.
Before you email
- Tell us your phone model and whether it’s iPhone or Android.
- Tell us what you tapped and what you expected to happen.
- Please don’t send backup files unless we ask. They can contain your records.
Results are planning estimates only, not engineering or electrical advice. Have a licensed electrician review any installation.