Installers have plenty of options when it comes to choosing an inverter for a solar carport project since they aren’t required to comply with rapid shutdown codes. Still, string inverters are the favorite choice for these installations for a number of reasons.
Los Angeles-based installer American Solar Power (ASP) prefers to install string inverters in carport arrays because they’re compact and simple. The company tries to stay away from string inverters that must be paired with optimizers to operate, because then the installation and O&M plan become more complicated.
“The wire management is challenging on the optimizers,” said Edwin Baranian, owner of ASP. “It just has a lot of tedious extra work to polish up the project.”
Steven Roseborough, director of commercial operations at ASP, said optimizers are also usually the first piece of a solar project to fail. Since they’re mounted underneath the modules, swapping these out on carport installations typically requires renting a scissor lift to reach them.
String inverter maintenance usually only requires a ladder for ASP unless the inverter is broken and needs to be replaced. In most cases, maintenance workers can climb a ladder to the inverter, hook up a laptop to troubleshoot, then swap out faulty fuses or terminals.
Replacing a whole, heavy unit takes more time and money, so Baranian suggests that system owners install reliable, well-reviewed inverters to try to ensure longevity.
“If I have any advice, it would be to use equipment that has a track record of operation,” Baranian said.
In addition to maintenance and mounting considerations, installers should choose inverter brands that are proven to perform well in outdoor conditions.
“The products that can handle really low temperatures as well as very high temperatures without effectively exceeding their ability to operate, those are the ones you want to install,” said Michael Mills-Price, head of inverter and energy storage business at PV Evolution Labs (PVEL). PVEL published its first PV Inverter Scorecard in 2019.
Most inverters installed in carport arrays will be shaded by the structure, unlike some roof-mounted inverters, but will still be exposed to weather and higher daily operational temperatures than those sheltered in a garage.
Along with natural wear and tear on the inverter, installers must take precautions to make sure people don’t damage them, accidentally or intentionally.
“When they’re out in the open like that and you’ve got anything that can be flipped, switched or turned or anything like that, it’s nice to get it up out of the way,” said Don Peek, director of commercial design for California installation company Sunworks. “I mean, anybody determined can go up and still mess with things, but most people don’t.”
Mills-Price said the ideal mounting solution for string inverters would be at the ground level in a locked cabinet, but usually there isn’t space for that in the parking lot layout. Most installers instead mount string inverters high enough on the steel beams that people can’t touch them.
Peek said the majority of inverter manufacturers are conscious of vandalism risks and design secure mounts and hidden bolts so inverters can’t be ripped off poles.
“If you make it too easy to steal, it’ll disappear,” Peek said.
Manufactured mounting points
Although installers can use the same bracket as in a garage installation to mount string inverters on poles, mounting on steel is much different than wood.
“I’ve seen our guys installing these inverters and trying to drill through I-beam steel and just burning through bits,” said Darren Kelly, manager of business development and marketing at Baja Carports. “It’s something they’re not used to. They’re used to drilling into wood, mount that thing and get out of there. Now they’re drilling into steel.”
Baja Carports offers a way to avoid that onsite hassle. The company consults with installers during the carport manufacturing process, plots exactly where inverters will go on the poles, and pre-drills mounting holes at the factory.
“On steel, everything’s harder,” Kelly said. “Anyone could drill into wood no problem. But on steel, we have to consider where everything goes so that it can be done in the shop versus in the field.”
Nontraditional carport inverter choices
If the installation is big enough for central inverters to make financial sense, Mills-Price said this inverter type can be a great option for carport installs.
“You can put a single inverter to cover the three or four carports depending on how they’re laid out, tie them all into one location. Central inverters are ground-mounted by nature, and you’d have one service location,” he said.
Central inverters would need to be protected by some type of gate or fencing for safety, but maintenance could be performed at ground-level.
Mills-Price said even microinverters can be a good choice for carport installations. Since they’re usually mounted to the back of the panel or to the racking itself, there’s no need to find a place for them on the poles.
“If your carport’s a little complicated, a little spread out or something like that, a microinverter might be a good choice,” Sunworks’ Peek said. “It separates the strings a little bit more.”
Microinverters also offer superior monitoring since they’re module-level power electronics. Peek said O&M is not much more difficult with micros than strings. Since most of Sunworks’ carport installations are 12 ft high or less, a 10-ft ladder is all his team needs to swap out microinverters or string inverters.
Still, Peek prefers string inverters on carport installations since they’re simple but still give installers the reliability of multiple inverters on a larger system.
“It’s kind of the good medium between the two extremes, and it’s cost effective too,” Peek said.
No matter what type of inverter installers choose for carport installations, picking one that’s proven to work best outside and taking steps to prevent vandalism will ensure the longest lifespan possible.