Home Solar Arrays

Crystalline Silicon Arrays

• In a crystalline silicon panel, solar photovoltaic cells are typically enclosed behind glass in a metal frame that is then mounted in racks to form an array -- at either ground level or on the roof. The entire array can be positioned at an angle that maximizes exposure to the sun to help this technology produce more electricity per square foot. In recent years silicon panels have commonly used one of four types of photovoltaic cells: monocrystalline, multicrystalline, polycrystalline and amorphous silicon, listed in the order of their electrical output. The terminology describes the silicon's crystalline matrix as seen under a high-magnification microscope.

Thin-Film Arrays

• Thin-film arrays are a lighter-weight alternative to crystalline silicone panels, and can usually be mounted flush to the roof without the need for structural reinforcement. Thin-film systems provide a little less electricity per square foot than crystalline silicon modules, but they are available at lower cost and are less expensive to install. Because they don't protrude above the roof deck, thin-film arrays are also less vulnerable to wind shear, and that makes them a good choice for homeowners in tornado or hurricane-prone regions. Thin-film cells are most often based on amorphous silicon, cadmium telluride, or copper indium gallium selenium (CIGS) cells.

The Best Location for a Home Solar Array

• For best performance, a solar array should face south in a portion of your lot that is exposed to constant sunlight 12 months of the year. Neighborhood zoning rules may prohibit homeowners from installing rack-mounted solar arrays where they are visible from the street for aesthetic reasons. If that's the case, you need to choose between a less obtrusive thin-film array on the roof or a ground-mounted array in the backyard. Some thin-film systems are designed to blend with black shingles so they appear to be part of an ordinary roof.

Solar's Bottom Line

• Using today's technology, a south-facing rooftop solar array can provide 40 to 50 percent of your home's electrical needs and even allow you to sell excess energy back to your utility provider. Depending upon the system you choose, you can expect to recoup the cost of an installed home solar array in 10 to 20 years. Although the electrical output of your solar array diminishes over time due to weathering, it's not uncommon for photovoltaic systems to be productive for over 30 years. Both federal and state governments offer financial incentives that bring down the cost of installing solar energy. The U.S. Department of Energy offers an online database of state incentives for renewable energy and energy efficiency initiatives. The database, DSIRE, shows which money-saving opportunities are available in each community for individuals wishing to add solar to their home.