The most efficient tilt for photovoltaic panels in Manchester, New Hampshire at a latitude of 42.98°:
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 35.8°.
If you're planning to change the angle of your photovoltaic panels twice per year, the most efficient angle is 19° in summer months and 56.8° in winter months.
If you're planning to change the angle of your photovoltaic panels each season, the most efficient angle is 15.2° in summer months and 62.3° in winter months, and 39.8° in autumn and spring months.