Insolation is a measure of solar radiation energy received on a given surface area in a given time. The  electrical output of your array is largely a factor of its insolation, which is based on its Azimuth, Pitch, and Shading.

Insolation is a measure of solar radiation energy received on a given surface area in a given time. The  electrical output of your array is largely a factor of its insolation, which is based on its Azimuth, Pitch, and Shading.

The earth's rotation and revolution around the sun create a rectangular section through which your home receives direct sun all year, i.e. The Solar Window. This diagram shows how the rectangle of  E-W and N-S movement is described on our sphere.

Azimuth is the direct your roof faces. (This diagram oddly shows South as upward.) With the sun always to our south, roofs with southern facings are optimal, although East and West can be good as well.

This Compass shows the directions with their angles in degrees. A compass does not account for magnetic declination, however. Magnetic declination is the angular difference between Magnetic North and True North. Currently, San Francisco has a magnetic declination of about 14.6 degrees west of True North. A roof with an azimuth of 194.6 degrees is optimal for our region.

Pitch is the angle of your roof. The azimuth and the pitch combine to determine the amount of direct sunlight your roof will receive. A 20 degree pitch on a south facing roof is perfect, but special racking allows panels to be tilted to the desired degree, even on flat roofs.

Solar Sweet Spot - This chart indicates the percentage of direct sunlight that will fall on a roof at a range of azimuths and pitches. The closer to the sweet spot, the higher the output of your array.

Shading - When the sun goes away, so does your power. This Sun Path Finder shows where shadows will fall all year round. You can see the reflection of a tree in the top, which will shade the array from 11-Noon in the winter months.

Efficiencies - When you put all these factors together, along with the charge losses from the movement of electricity through the system components and wiring, you come out with a total efficiency rating. The CSI website has a calculator to estimate the total output and your rebate from that.

The earth's rotation and revolution around the sun create a rectangular section through which your home receives direct sun all year, i.e. The Solar Window. This diagram shows how the rectangle of  E-W and N-S movement is described on our sphere.

Azimuth is the direct your roof faces. (This diagram oddly shows South as upward.) With the sun always to our south, roofs with southern facings are optimal, although East and West can be good as well.

This Compass shows the directions with their angles in degrees. A compass does not account for magnetic declination, however. Magnetic declination is the angular difference between Magnetic North and True North. Currently, San Francisco has a magnetic declination of about 14.6 degrees west of True North. A roof with an azimuth of 194.6 degrees is optimal for our region.

Pitch is the angle of your roof. The azimuth and the pitch combine to determine the amount of direct sunlight your roof will receive. A 20 degree pitch on a south facing roof is perfect, but special racking allows panels to be tilted to the desired degree, even on flat roofs.

Solar Sweet Spot - This chart indicates the percentage of direct sunlight that will fall on a roof at a range of azimuths and pitches. The closer to the sweet spot, the higher the output of your array.

Shading - When the sun goes away, so does your power. This Sun Path Finder shows where shadows will fall all year round. You can see the reflection of a tree in the top, which will shade the array from 11-Noon in the winter months.

Efficiencies - When you put all these factors together, along with the charge losses from the movement of electricity through the system components and wiring, you come out with a total efficiency rating. The CSI website has a calculator to estimate the total output and your rebate from that.