The most efficient tilt for photovoltaic panels in Honolulu, Hawaii at a latitude of 21.33°:
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 18.56°.
If you're planning to change the angle of your photovoltaic panels twice per year, the most efficient angle is -1.2° in summer months and 37.9° in winter months.
If you're planning to change the angle of your photovoltaic panels each season, the most efficient angle is -4.7° in summer months and 43° in winter months, and 18.6° in autumn and spring months.