The most efficient tilt for photovoltaic panels in Tacoma, Washington at a latitude of 47.24°:
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 39°.
If you're planning to change the angle of your photovoltaic panels twice per year, the most efficient angle is 22.9° in summer months and 60.5° in winter months.
If you're planning to change the angle of your photovoltaic panels each season, the most efficient angle is 19.2° in summer months and 66° in winter months, and 44° in autumn and spring months.