A single rooftop PV panel sits east of a taller neighboring building. Instantaneous unshaded output follows the standard PV power equation:
P = η · I₀ · sin(alt) · A
η = panel efficiency (20%)
I₀ = 1000 W/m² (peak solar irradiance)
alt = solar elevation angle
A = panel area (10 m²)
Solar elevation and azimuth come from the standard hour-angle formula for a mid-latitude city (φ = 45°N), with a real seasonal declination computed from the day of year N:
δ = 23.44°·sin(360°/365·(N−81))
H = 15°·(hour−12)
sin(alt) = sinδ·sinφ + cosδ·cosφ·cosH
The neighboring building's shadow length on flat ground is the exact geometric relation for a vertical wall:
shadow length = height / tan(alt)
In the morning the sun sits in the east and the shadow falls west, away from the panel. In the afternoon the sun swings west and the shadow falls east, toward the panel. Whenever the sun is on the afternoon side and the shadow length reaches or exceeds the separation distance, the panel sits fully in shadow and contributes zero output for that instant — otherwise it runs at full unshaded output. The daily yield curve integrates this instantaneous power across the whole day, so a taller neighbor or a narrower gap widens the shadowed window and visibly deepens the afternoon dip, cutting total daily energy.
Neighboring building height and separation distance rebuild the street canyon. Time of day and Run day cycle sweep the sun from sunrise to sunset. Day of year moves the sun's seasonal declination, changing how high it climbs at noon.