The first serious step in a solar project is the site assessment — a careful look at the property to determine where panels can go and how well they will perform there. Assessments examine several factors together.
Roof orientation and tilt
In the northern hemisphere, south-facing surfaces capture the most direct sunlight across the day; in the southern hemisphere, north-facing surfaces do. The roof's pitch matters too: a tilt near the site's latitude generally intercepts sunlight well, though panels can be mounted at other angles or on flat roofs with support structures. Orientation and tilt are inputs to a generation model, not pass-or-fail tests.
Shading
Trees, chimneys, dormers, and neighboring buildings cast shadows that reduce output — and a shadowed corner can hold back more than just its own share of the array. A good assessment looks at shading through the year, including how winter shadows, when the sun rides lower, differ from summer ones. Sometimes trimming or removing a tree is an option; sometimes the array is simply placed away from the shade.
Roof age and condition
Modules carry real weight, and they typically stay in place for decades. The roof must be able to bear the array, and its covering should have enough life left that panels will not need to be removed and reinstalled for a re-roofing soon after. An older or weak roof may need repairs or replacement first — a cost and a decision worth surfacing early.
Available unshaded area
In the end, the assessment produces a map of usable, unshaded area — the space that can actually hold modules productively. That area, combined with your electricity use, sets the realistic upper bound on system size.