The tolerance is wider than you think
Many homeowners fret over being 10-15° off south. Don't — the yield loss is under 2%. The real disasters are panels facing north (unusable in India), facing directly east-west (22% loss), or split across badly-oriented sections of a hip roof. Focus your worry there, not on getting exactly 180°.
When east-west split makes sense
On flat roofs, a ballasted east-west system (panels tilted back-to-back in rows) is increasingly common: higher packing density, smoother production curve, better for net-metering under time-of-day tariffs. Total yield is 85-90% of optimal south — but you fit 25-30% more kW on the same roof. Net result: similar or higher total output.
India\'s magnetic declination is tiny
Unlike North America (where magnetic and true south can differ by 15°), India has magnetic declination in the -1° to +3° range. Your smartphone compass reading is essentially true south. Still, for precision, calibrate the compass first (walk in a figure-8) and verify against the noon sun position.
Azimuth pairs with tilt and irradiance — fine-tune the full orientation with our Tilt Angle Calculator, check Peak Sun Hours for your city, and confirm the panel count with the Roof Area Calculator.