The lifetime cost issue of solar -- and one that many people never consider -- is that rooftop PV systems may have to be removed and reinstalled if the roof needs replacement or repairs, which is almost a certainty with asphalt/shingle roofs. While PV systems typically lose a small portion of their potential output (less than 1 percent each year), the systems can operate for decades longer than the typical residential or commercial roof (10-12 years in Georgia). In other words, roofs are likely to be replaced at least once during the typical life of a PV system.  According to a report from GRIST.ORG, reinstalling a residential rooftop PV system could cost $6,250 or 25 percent of the installed cost of the system. In our investigation, we found that moving residential PV systems to accommodate a roof replacement could cost as much as 25 percent of the initial system cost (and over 35 percent of the net cost after the application of the 30 percent federal tax credit). Moving systems on a commercial roof was less expensive, on the order of 15 percent of initial installed cost (around 25 percent of the system cost after the tax credit). Source text.