The amount of open/unobstructed roof space, simply put, will determine how many solar panels you can attach to your roof. The greater the amount of solar panels, the greater the energy production one can achieve. Roofs that are relatively flat and do not have obstructions, such as dormer windows, chimneys or vents, are ideal.
The direction your roof faces is a significant factor to take into account when considering whether or not to purchase a solar system for your home or office. A south-facing roof is ideal, while a north-facing roof will not suffice for solar; however, one can do quite well with a southwest- or southeast-facing roof. If the roof is completely flat, which is the case for some modern residential homes and commercial buildings, it can be considered ideal for installing solar panels if there is also minimal roof obstructions and shading.
Shading is also another determinant factor for solar. Shading will obviously obstruct the sun’s rays and thus reduce the amount of energy that can be produced. If shading is caused by a moveable object, such as a tree, it can make an unviable situation viable again with tree work by an arborist. Other unmovable shading objects like neighboring buildings provide greater challenges. Sometimes a ground mount can be explored as a last resort. Shading is an issue in the Northeast United States, so moderate to light shading is sometimes a compromise a solar customer has to make.
This south-facing roof with absolutely no shading issues would be the perfect candidate for solar.
This roof faces southwest and has trees on the property with light shading by some trees. However, nothing surrounding this building would significantly obstruct the solar panels.
This roof on this building is nearly flat, which is good; however, it faces west which is satisfactory but not ideal. The principal problems stem from the shading from the tall trees and building next door.