The most efficient tilt for photovoltaic panels in Manhattan, New York at a latitude of 40.78°:
Your photovoltaic panels need to be angled facing south.
If you're mounting the photovoltaic panels at a stationary angle, such as on your roof, the most efficient angle is 34.1°.
If you're planning to change the angle of your photovoltaic panels twice per year, the most efficient angle is 16.9° in summer months and 54.9° in winter months.
If you're planning to change the angle of your photovoltaic panels each season, the most efficient angle is 13.2° in summer months and 60.3° in winter months, and 37.7° in autumn and spring months.