Inverters are an essential and critical component in any PV system. Without them, the DC produced in the panels would not be used to power AC appliances rendering the PV system ineffective. On the other hand, optimizers will create a more efficient DC output than one without it.
Micro-inverters and optimizers are both classed as Module-Level Power Electronics, and while they have similar characteristics, they perform different roles. The optimizers condition DC and send it to a central inverter while micro-inverters convert the DC to AC at the panel.
Let’s analyze the differences and similarities between these two in more detail and how they increase the efficiency of the production and conversion of DC to AC in the PV system.
What Are Inverters And Why You Need Them
Inverters convert the DC produced in the solar panels to AC to power appliances in the home. Unless the system is driven directly from DC, which often doesn’t happen, inverters are the PV system’s essential ‘middle-men.’
The Three Types Of Inverters
The oldest and most installed inverter system is the string inverter, as these are proven and reliable technology and are cost-effective. Microinverters and optimizers are relatively new, but they prove their worth in applications.
String inverters are fed by all the linked solar panels and operate at the level of the weakest panel since the panels are all connected.
Microinverters convert the DC to AC at the panel and send that directly to the fuse-box and grid, making your solar system more efficient.
Optimizers’ optimize’ the central inverter’s AC energy for AC conversion.
The Similarities Between Optimizers and Micro-Inverters
These two components have some similarities in that they are each fitted to the individual solar panel. They help improve generation efficiency on roofs that experience shade during the day or have complex configurations.
Moreover, they both can monitor the individual panel output in kWh in the solar array. This assists with balancing the power outputs through the system and seeing which panels are more efficiently positioned than others.
Installers will place one of either on each panel of the array, so regardless of the size of the array and number of panels, you will have either a micro-inverter or optimizer on every panel.
Optimizers And Micro-Inverters Have Similar Lifespans
All reputable manufacturers of solar PV components will back their products with warranties, and these components often have good warranties of around 25 years, which speaks volumes about their longevity.
Whether you have microinverters or optimizers, they will last as long as your solar panels will, and that’s peace of mind for the homeowner and purchasing high-quality micro-inverters and components is critical for performance and longevity.
While these components have good longevity, the central inverter on the system often has a lesser warranty, and many installers will extend the warranty on the main inverter as part of the package or at an extra cost.
In most cases, your main inverter is more likely to fail as it only has a 12-year warranty. This means that you may end up replacing your main inverter halfway through the system lifetime rather than the microinverter or optimizer.
It will be cheaper to replace a string inverter at ground level than replacing roof-mounted inverters or optimizers, as they will require more time and labor to access the roof.
Now, let’s look at the differences between them.
Where The Conversion Of DC To AC Happens
This is one of the main differences between the two components as they convert the DC to AC at different points in the system.
Optimizers are designed to ‘optimize’ or ‘condition’ the DC produced in the PV panels, allowing the central inverter to operate more efficiently when converting DC to AC.
By fixing the DC voltage before it gets to the central inverter, the optimizer allows the main inverter to provide optimum AC production and current to the system.
Microinverters convert DC to AC at the panel and distribute the power back to the grid and fuse-box. These are best suited for grid-tie systems as you also won’t need a central inverter, while off-grid would be better suited to optimizers or string inverters.
Compatibility With Storage Batteries
Another big drawback is that microinverters aren’t well suited to systems using DC battery banks as storage. They supply AC direct rather than DC, so the electricity produced cannot be stored the same way with DC batteries.
However, microinverters can work with an AC-coupled battery solution so that you can have that discussion with your installer. Remember that microinverters are designed to work where roofs may experience shade or have difficult angles involved.
Be sure that you need microinverters as they will cost more than either the string inverter or optimizer, and if you don’t need them, don’t install them.
Micro-Inverters VS Optimizers And System Performance
Here is where micro-inverters have a distinct advantage. Central inverters will only produce as much power as the lowest-performing solar panel. So if there is one panel in the shade or is covered by dirt and that panel’s efficiency is lower than the rest, that is the output that the system will operate on.
With microinverters, the system will not lose generation capacity if one panel is not operating at maximum, and they provide constant updates on voltage output and cell temperature. Hence, the homeowner knows which panel is struggling and which are not.
Microinverter Disadvantages
The biggest disadvantage of micro-inverters is that they are more expensive than other inverters and would cost more to replace or repair if they fail. Since each panel must have an inverter, installing one on each panel vs. a central inverter is more costly.
The downside of microinverters is that they are often grid-dependent, and if your grid goes down, your system can, too, unless you have your system optimized for AC coupling.
With most microinverters, the individual panel monitoring may only be available with an upgrade which would add to the cost.
Conclusion
As the technology of these components evolves, the onus rests on the homeowner to have open discussions about realistic power requirements for their home and not get ‘sucked’ into a system that isn’t the best option.
But one thing is for sure that the use of optimizers or micro-inverters is changing the landscape of domestic PV systems for the better.