| People who glance at a roof with solar panels in place | | | | The systems that return the best performance are |
| don't realize the multiple factors behind their design | | | | pole mounted and actively track the sun. |
| and placement. Incorrectly calculating one element of | | | | Computer-controlled motors move the PV panels. |
| a solar power system can dramatically reduce the | | | | The goal is to keep the surface precisely |
| equipment's power-generating capacity. | | | | perpendicular to the sun, thus maximizing light capture |
| One of the most important factors to consider | | | | and energy production. Tracking technology will |
| before roof or pole-mounting photovoltaic cells is the | | | | increase energy production in a given system by |
| degree of shading present. Individual cells are | | | | 25% over stationary units. |
| arranged in arrays or series on single photovoltaic or | | | | Magnetic declination is also a factor, a detail of which |
| "PV" panels. Shade falling on just one cell can shut | | | | most solar power neophytes are completely |
| down the whole series, including cells that are in full | | | | unaware. To achieve the proper angle for the panels, |
| sun, and can create a current drain throughout the | | | | the difference between the magnetic poles of south |
| system. | | | | and truth south must be added or subtracted. |
| The degree of light the panels will receive is also a | | | | Minneapolis, for instance, has an almost zero |
| major concern. Latitude and cloudiness are the | | | | adjustment for declination, while Seattle's is |
| greatest factors in determining luminosity. Two | | | | approximately 19 degrees. Declination maps must be |
| identical power arrays installed at the same latitude, | | | | consulted for correct orientation of the array. |
| for instance one in Seattle and another in Spokane, | | | | Finally, the relative performance of PV panels will |
| WA, will provide radically different amounts of | | | | vary by manufacturer and model. It's best to read |
| electricity. The panel in Spokane, which receives | | | | independent reviews in addition to consulting the |
| semi-desert levels of sun will outperform the panel in | | | | product specification sheets to make a good |
| perpetually cloudy Seattle. | | | | evaluation. The highest performing residential solar |
| The panels should be tilted at approximately the | | | | power systems will likely be so expensive that full |
| same angle as the site's latitude and, in the northern | | | | amortization in net electricity savings will be |
| hemisphere, they cannot face more than 15 degrees | | | | impossible. With good choices and a careful |
| off due south. Optimal tilt during the summer months | | | | consideration of all relevant factors, however, |
| would be 15 degrees less than the area's latitude, and | | | | substantial electrical savings are possible, which is why |
| in winter 15 degrees more. Many residential roofs | | | | residential solar power generation continues to grow |
| have neither the angle nor the correct orientation to | | | | in popularity. |
| capture the best sun in all seasons. | | | | |