With most of the United States now requiring module-level power electronics (MLPEs) to comply with rapid shutdown requirements, solar installers have a choice between DC optimizers or microinverters. While these two options are distinct, the difference between purchasing and installing microinverters separately or installing AC panels is not as well known.
AC panels are considered premium panels. They come with a microinverter integrated into the back of the panel and are sold as a single unit. They also have a set warranty for both the panel and the microinverter -- typically matching that of the microinverter at 25 years. The warranty is usually serviced by each manufacturer separately, but often there is a single point of contact for the warranty claim process.
What makes an AC panel better than a traditional solar panel in combination with a standalone microinverter?
Having the microinverter already attached to the solar panel can simplify design, permitting, and, most importantly, installation.
AC modules essentially remove the DC portion of a solar PV system -- this means there are no DC cables, connectors, junction boxes, or combiner boxes to deal with. Both the PV designer and the plan checker do not need to worry about checking for high DC voltage, appropriate DC wire sizing with temperature safety factors, or unsafe inverter overdriving. The manufacturer has already ensured the panel plus microinverter combination is compatible, code-compliant, and safe.
When it comes to installation, AC panels can save significant labor time in the field. Because the microinverter is already integrated with the panel, installers don’t have to spend time independently bolting microinverters to the rail or the frame lip of the panel, or managing and securing the DC cable leads of the panels with wire clips. If the installer lays out the AC trunk cable beforehand, it becomes an easy plug and go solution.
Working with AC panels is also safer. When a solar panel is exposed to sunlight, it is energized, which means it is not good practice or safe to connect or disconnect the DC connectors from a microinverter or DC optimizer, as this can damage the connector and can also be a shock hazard for the installer. Often installers work-around this by covering the panels during installation, which is a hassle and time-consuming. With the microinverter already connected on the DC side of the panels, AC panels will not output any current or voltage unless they detect a utility grid signal. It is perfectly safe to disconnect and reconnect them from the AC trunk cable during the day, as long as they are not connected to the grid and are not operating.
What are the downsides of AC panels?
AC panels do have some downsides, and one of them is their cost. AC panels tend to be more expensive than the solar panel in combination with a standalone microinverter. In buying AC panels, consumers are paying a premium for the convenience of having an integrated unit that is easier and safer to install.
In addition, troubleshooting and replacing the microinverter from an AC module is a bit more involved. Typically, when a solar panel is not producing as it should, it isn’t always easy to determine whether the panel is malfunctioning or the microinverter. A workaround is to move the microinverter in question to another panel or use a different microinverter with the panel in question, and observe if the new panel and microinverter combination works properly. Doing this maneuver with an AC panel is more involved.
The choice between an AC panel or a DC panel plus standalone microinverter comes down to paying a little extra for added safety and ease of design and installation.