Inverters, Microinverters, & Power Optimizers - Guide for Homeowners

To create and use solar power at home, rooftop PV systems are made up of much more than just solar panels.


Although homeowners do not necessarily need to understand the inner workings of all of the components of a solar energy system, there are a few key technologies to know when considering a new residential installation.


Below, we’ll take a look at the differences between inverters, microinverters, and power optimizers to help you install the best possible solar energy system for your home and budget.

back of solar panels gound mounted
An array of solar panels without any MLPEs

String Inverters vs. Microinverters


When sunlight hits a solar panel, the electricity is initially generated as a direct current (DC). However, to be used safely within a home (or sent to the power grid), DC electricity must be converted into alternating current (AC).


To accomplish this, most modern solar energy systems use either string inverters or microinverters, depending on the unique variables of the installation.


String inverters: Connected to multiple solar panels at once, string inverters are the most common and cost-effective technology for converting residential solar power generation into usable electricity.


Also known as “central inverters,” traditional string inverters work well with “strings” of solar panels that are all producing approximately the same amount of electricity. For example, a set of 8 solar panels all facing the same direction without any shade-causing obstructions would likely utilize a string inverter.


Microinverters: An alternative to string inverters, microinverters are “Module-Level Power Electronics” (MLPEs), that convert DC electricity into AC electricity, one panel at a time. Microinverters are often affixed to the undersides of individual solar panels and are most suitable for installations in which the panels are generating various amounts of solar power at once.


Like how a “chain is only as strong as its weakest link,” the power produced by a set of solar panels connected to a string inverter is typically limited by its lowest-producing module. Here, microinverters mitigate this inefficiency by converting the energy produced by each panel individually and then sending it to a home, battery, or grid.


What are Power Optimizers?


Like microinverters, power optimizers are designed to make up for the shortcomings of string inverters. As another MLPE, power optimizers are connected to individual solar panels so that the DC energy generated at various capacities can be more efficiently converted into AC power.


Added to a string inverter system, power optimizers help each “string” of solar panels avoid lower overall production levels when one panel within the chain is underperforming.


Microinverters vs. Power Optimizers


With similar functionality, both power optimizers and microinverters are designed to help solar energy systems continuously produce as much electricity as possible. With either technology, homeowners can monitor the performance of individual solar panels and maximize electricity production when singular parts become exposed to shade, malfunction, or shut down.


Here, the key difference to know between the two technologies is the moment in time when the electricity is actually “inverted.” While microinverters immediately convert DC power into AC electricity, power optimizers merely “condition” the DC electricity before it is sent to a central, string inverter.


This step is crucial if you are considering adding solar storage. With power optimizers, solar can travel as conditioned DC electricity to a DC battery before it reaches the string inverter. In a microinverter system, power modified into alternative current (AC) must be then re-modified so that it can be stored as direct current (DC) in a solar battery.

A typical wiring arrangement for a power optimizer + string inverter system

Knowing this, off-grid and hybrid microinverter systems typically require a critical load panel (or subpanel) to be installed, which can be extremely expensive. Using power optimizers, there is typically less electrical work upfront, so to keep installation costs as low as possible, we typically recommend our customers install a traditional string inverter with added power optimizers when necessary.


Conclusion


In the end, both microinverters and power optimizers are designed to maximize solar energy production. For those going solar at home, familiarity with these technologies will make it easier to talk to solar companies about options and whether or not they make sense for your installation.


Want to talk about going solar in Colorado? Contact Apollo Energy today for more information.


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