The short answer
JinkoSolar's manual says about 10–15% of power output at 30° off due south, and 20–30% at 60° off.
Plain explanation
The JinkoSolar installation manual gives a rule of thumb for orientation: modules facing 30 degrees away from due south (northern hemisphere) lose roughly 10% to 15% of their power output, and at 60 degrees away the loss is 20% to 30%. Real losses also depend on tilt and latitude, so use it as a first check and confirm with a yield simulation for the actual site.
Steps from the source
- Measure the roof azimuth
- Use the manual figure only as a quick estimate
- Run a site yield simulation with real tilt and location before quoting kWh
"Modules facing 30 degrees away from due South (or due North) will lose approximately 10% to 15% of their power output. If the module faces 60 degrees away from due South (or due North), the power loss will be 20% to 30%."
Word for word from the source.
Source
JinkoSolar Global Installation Manual 202605 A1.8-EN, Section 3.1 Climate/Environment conditions and site selection, PDF p. 10jinkosolarcdn.shwebspace.com ↗
Where installers ask this
- South vs southwest facing panels (r/solar)
- reddit.com/r/solar/comments/187evmv/does_my_roof_directions_make_sense_for_solar/
General guidance based on the manufacturer's manual or the named source. Always follow the current manual for your exact model and your national code. DC and AC electrical work is for qualified installers only. Not affiliated with or endorsed by any brand named; trademarks belong to their owners.