of the entire array. Each microinverter harvests optimum power by performing maximum power point tracking (MPPT) for its connected module. Simplicity in system design, lower amperage wires, simplified stock management, and added safety are other factors introduced with the microinverter solution. The primary disadvantages of a microinverter include a higher initial equipment cost per peak watt than the equivalent power of a central inverter since each inverter needs to be installed adjacent to a panel (usually on a roof). This also makes them harder to maintain and more costly to remove and replace. Some manufacturers have addressed these issues with panels with built-in microinverters. A microinverter has often a longer lifespan than a central inverter, which will need replacement during the lifespan of the solar panels. Therefore, the financial disadvantage at first may become an advantage in the long term. A power optimizer is a type of technology similar to a microinverter and also does panel-level maximum power point tracking, but does not convert to AC per module. Description String inverter Solar panels produce direct current at a voltage that depends on module design and lighting conditions. Modern modules using 6-inch cells typically contain 60 cells and produce a nominal 24-30 V. (so inverters are ready for 24-50 V). For conversion into AC, panels may be connected in series to produce an array that is effectively a single large panel with a nominal rating of 300 to 600 VDC. The power then runs to an inverter, which converts it into standard AC voltage, typically 230 VAC / 50 Hz or 240 VAC / 60 Hz. The main problem with the string inverter approach is the string of panels acts as if it were a single larger panel with a max current rating equivalent to the poorest performer in the string. For example, if one panel in a string has 5% higher resistance due to a minor manufacturing defect, the entire string suffers a 5% performance loss. This situation is dynamic. If a panel is shaded its output drops dramatically, affecting the output of the string, even if the other panels are not shaded. Even slight changes in orientation can cause output loss in this fashion. In the industry, this is known as the "Christmas-lights effect", referring to the way an entire string of series-strung Christmas tree lights will fail if a single bulb fails. However, this effect is not entirely