Solar Equipment: Inverters, Solar Panels, and Sunlight. What else do you need?
The solar inverter is the second most important (and second most expensive) component of a solar PV system. It’s important because it converts the raw Direct Current (“DC”) solar power that is produced by your solar panels into the “plug-the-toaster-in” Alternating Current (AC) power that comes out of your wall sockets. Inverters also have technology that maximizes the power output of that DC energy. There are two basic types of inverters.
Central inverters are well-tested and reliable systems that have been around for decades. These are the most common types of inverters. With central inverters, every solar panel is wired in a “string” to the inverter box. The conversion from DC to AC occurs at one central location, such as your garage. Because the solar panels are wired in “series,” each panel’s power output depends on all of the panels working. Think of a string of Christmas tree lights. If one bulb goes out, the whole string of lights go out until the bad bulb is replaced. So, if shade from a tree hits one panel, it can seriously diminish the power produced by the whole solar system until the shade clears. This is why an accurate shade analysis is so important.
Micro inverters are relatively new to solar. Instead of converting the DC to AC power at a central location, micro inverters are installed right under each solar panel. The main advantage to micro inverters is the ability for each solar panel to transmit power into your home. In other words, each panel is its own solar powered island and keeps churning out solar watts regardless of what happening to the panel beside it. The down side of micro inverters is that they can be more expensive and take more labor cost to replace each inverter. Also, because they’re so new, micro inverter reliability is unproven outside of lab testing.
Central inverters typically carry a 10 year warranty and often go for 12 to 15 years or longer. The leading micro inverter company has a 15 year warranty, but the inverter(s) could last years longer too. In either case, if you stay in the same house for 20+ years with your same solar panels, (which last 20 to 25 years or longer) expect to pay to replace your inverter(s) at some point. How much? Due to manufacturing advances in 15 years, probably less than the current cost of about $1200-$2000. But who knows? Could be about the same price. Time will tell.
The BOS (Balance of System)
There are many other less well known and less expensive parts to a solar system. Installers typically wrap these up into “The BOS” or “Balance of System.”
The balance of system includes components such as wiring, emergency DC disconnects, system monitoring hardware, the frames or “racking” that holds your panels to the roof and at the right angle, nuts, bolts, roof “flashing” to prevent leaks, and more.
The balance of system components required to attach solar panels to your roof is covered in the Nitty-Gritty on Solar Roofing.