The early horror days for inverters, when a 20 percent failure rate was said to be common, now seem to be safely behind the PV industry. Inverters were once responsible for 80 percent of PV system failures, when lifetimes projected by manufacturers were under five years.
Now more long-term focused owners are far more interested in the quality of Tier 1 suppliers and in the stronger warranties and warranty extensions they offer, says Laks Sampath, the U.S. and Latin America manager for Alectris, a solar asset management company.
While a few installers or EPCs may still make purchase decisions on lowest cost, those cases likely mean that they carry no or little responsibility for the warranty on the inverters they select. But PV system owners, operators and maintenance companies with a longer outlook now stick with manufacturers that stand behind their systems, says Sampath. HIs company manages dozens of central inverters and dozens of string inverters used in 200 plants under management worldwide.
“The high quality of some inverters is surprising. At one plant, an overheated transformer was gutted but the inverters shut down like they were supposed to. When we opened the cabinet, charred from the heat, it still looked brand new, like someone had just polished it,” Sampath said.
One key reason the initial high failure rate of inexpensive inverters took place was a lack of a hermetic seal against dust and moisture; the adoption of this feature is virtually industry-wide now.
The advent of microinverters and power optimizers also has reduced operating temperatures from those that string inverters must withstand, at times leading to premature failure. Better, longer warranties are another reason failure rates have declined.
Central inverters typically come with five-year limited warranties, string inverters come with warranties of about 10 years and microinverters come with 25-year warranties. But many manufacturers and EPCs offer warranty extensions for all types of inverters for the 25-year life expectancy of the PV system. “Most of the main manufacturers have re-insurance for their warranties, so third-party warranties are less important now,” Sampath said.
Inverter warranty offers also are moving downstream from manufacturers and EPCs to installers. “Inverters just do not have a 25 year lifetime, and we want the system we sell you to continue to produce for 25 years, not 10 or 15 years. So Palomar Solar goes ahead does a pre-buy of the warranty for up to 25 years, guaranteeing coverage of the cost of the second inverter that you will need to have installed during the lifetime of your solar system,” Adam Rizzo, the co-founder of the Escondido, CA-based company states on his website.
Interested in quality issues? Be sure to register for our Quality Roundtable at the Solar Power International trade show in Las Vegas on September 12.