Considering a Small Solar Electric System

To help evaluate whether a small solar electric system will work for you, you should consider the following:

-Your available solar resource—do you have clear and unobstructed access to sunlight for most or all of the day, throughout the year?

-The system size—do you have a roof or area large enough to accommodate it?

-The economics—is it worth the investment?

-Local permits and covenants—are there any issues with installing a system?

Evaluating Your Site's Solar Resource for Solar Electricity

The solar resource across the U.S. is ample for solar electric systems because they can use both direct and scattered sunlight. However, the amount of electricity generated at a particular site depends on how much of the sun's energy reaches it. Thus, PV systems function most efficiently in the southwestern United States, which receives the greatest amount of solar energy.

Before you buy a PV system, you'll want to be sure your site has enough solar energy to meet your electricity needs efficiently and economically.


When evaluating your site, you'll also need to consider both the geographic orientation and the tilt of your solar panels as both can affect your system's performance.

Orientation

PV modules should be oriented geographically to maximize the amount of daily and seasonal solar energy that they receive. In general, the optimum orientation for a PV module in the northern hemisphere is true south. However, your modules can face up to 45º east or west of true south without significantly decreasing its performance.

If you plan to mount the modules on your roof, you'll also want to consider these factors:

-Roof orientation and condition

-Local landscape features that shade the collector daily or seasonally

-Local weather conditions (foggy mornings or cloudy afternoons) that may affect the optimal orientation and subsequent electricity production of the PV modules.

To be eligible for some rebates, your system must be unshaded between certain hours during certain times of the year. Some states also have laws that establish your right to protect your solar access through the creation of a solar easement.

If a rooftop can't be used, your solar modules can also be placed on the ground, either on a fixed mount or a "tracking" mount that follows the sun to orient the PV modules.

Tilt

Most PV modules are mounted flat on the roof, and so have the same tilt as the roof. Although the optimal tilt angle for your modules is an angle equal to your latitude, fixing the PV modules flat on an angled roof is generally not a problem. However, because most roofs are pitched at an angle less than the latitude, you and your contractor will need to factor your roof angle into the performance calculations when sizing your system.