PV modules perform better when directly facing the sun. In many cases the slope and orientation of your roof may be suitable for use as a mounting structure for the PV modules. A south-facing roof with a pitch of approximately 35° would be ideal in much of the US. Minor deviations to the southwest/southeast or roof pitches ranging between 25° and 60° may also be acceptable.

However, shade caused by trees, neighboring buildings or chimneys should be avoided. Another factor to consider when evaluating the roof as a mounting option is the amount of area available. A good rule of thumb is for 1000 Watts (1 kW) of power, allow 10 square meters of area. This means that if you would like to mount enough PV modules to produce 2 kW of power, the roof needs to be able to accommodate a PV array approximately 20 square meters in size. Your local solar power installer can perform a site evaluation to determine if the roof is a good option. Many solar installers offer this service free of charge.