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Difference between conventional central inverters and micro inverter?

A solar system consists of an array of panels connected in series of 'strings'. These are then connected to a single solar inverter which takes the direct current (DC) voltage and converts into alternative current (AC) voltage usable by your home or fed back to the electricity grid. The number of panels in a string will vary depending of the output capacity of the individual panels. Most panels will be connected in string lengths ranging between 5 and 13 panels. Inverters with one MPPT input will need the strings to be of equal panel lengths/output capacity.

Micro inverter

Micro-inverters are installed differently to conventional central inverters. Micro-inverters are attached to the underside of each and every panel in the solar panel system directly on the roof (sometimes there is one micro-inverter connected to two panels). Rather than aggregating DC power and sending down to a single inverter to convert to AC power, micro inverters convert the DC current from each panel to AC current. AC power from several micro-inverters is then combined and fed into an existing electrical grid via your switchboard.

Micro-inverters can have several advantages over conventional central inverters. The main advantage of a micro-inverter is that if there is partial shading on your roof from nearby trees, leaves, chimneys,  the output of an entire string of panels is not reduced, only the affected panel. with a string of panels shadowing issue will cause a loss of output from the complete system string. Each micro-inverter obtains optimum power by performing maximum power point tracking for its connected panel.

The primary disadvantage of micro-inverters is that they currently have a higher initial cost than the equivalent power in a central inverter. As well, the panel output capacity is limited, potential restricting the amount of power a roof can produce. This is becoming more critical as household solar demands increases to feed battery storage units. With multiple inverters, you also multiply the chances of a fault which is then harder to get to and hence more expensive to service. This is particularly important because as micro-inverters are located in a potentially very hot environment on the roof, their longevity is still to be seen in years to come.