Central Inverters and Microinverters
A solar inverter converts the variable DC output of the solar panels on your roof to a safe usable AC power that can be used in your home or fed into the utility grid (net metered). The inverter performs many electrical tasks simultaneously and acts as the “brain” of the PV system.
Traditional PV systems are designed around a central inverter. Solar Panels are arranged in “Series Strings”. The strings are connected “parallel” to the inverter. Because the solar panels are connected in series, problems can occur when individual models are shaded or when they have different directional orientations. In general, the worst performing module will tend to drag down the performance of the whole system.
This does not mean that central inverters are “bad” necessarily. For applications where the panels are all facing one direction, and where there are minimal shading issues, the central inverter is an economical, reliable and efficient solution. String inverter technology has come a long way in recent years: the introduction of ungrounded “transformerless” inverters has resulted in decreased size and cost. These “multi-channel” inverters allow for panels mounted in multiple directions with uneven numbers of modules in a “string”. They offer free web monitoring and even limited power supply when the grid is down. Central inverters are usually warranted for 10 years. Extended warranties are available at an additional cost.
A microinverter is a small PV inverter that is mounted beneath and connected to an individual solar panel on the roof. Microinverters are wired in parallel and connected directly or indirectly to the circuit breaker panel and ultimately to the grid (net metered). DC to AC conversion takes place on the roof. Because micro inverters are connected in parallel, rather than in series, they are a simple solution for applications where there are shading issues on multiple mounting places (Direction and Pitch). The use of microinverters allow solar panels to produce power independently as opposed to string (central) inverters which require panels to produce as a group. In some cases- not all, The use of microinverters will result in superior energy harvest. Micro inverter systems offer free web monitoring and a 25 year warranty.
In an optimized system, power optimizers are connected to and installed beneath the solar panels on the roof. The optimizers are connected in series and communicate with each other electronically, “conditioning” the DC power to compensate for shade and mounting place differences before sending the current to the inverter where it is converted to usable AC power.
In short, optimized systems incorporate some of the benefits of microinverters with some of the cost benefits of string inverters. Optimized systems come with free web monitoring at the module level and a 12 year warranty. Warranty extensions are available at extra cost.