Micro-Inverters Vs String Inverters
Pros and Cons of Rooftop Solar Inverter Types
For Rooftop Solar, homeowners have to make a choice between the conventional string inverters and the latest technology micro-inverters. Inverters convert direct current produced by the solar panels to alternate current used by most of the electrical appliances, machines, and lighting. A solar inverter is considered the brain of the solar system. We will first present the pros and cons of these two types of solar inverters.
A micro inverter is an inverter that works at the solar module level. It is connected to the output of every single module and the output from several such micro-inverters are fed to the grid. Whereas a string inverter is connected to a series of solar modules and the combined output of these modules is then processed by the inverter from DCÂ to AC and fed to the grid. Because a number of solar modules are connected in series to a single inverter, if just of the panels is obstructed by shadow or malfunctions for any reason, it affects the output of the whole series of the panels. Whereas, because each micro-inverter is connected to individual solar modules, any malfunction of the micro-inverter or shadow faced by any solar panel affects only the output of that panel.
Rooftop solar Installations using string inverters require more technical skills and safety precautions because of the high DC voltage involved compared to installation using micro-inverters. As far as ease of installations is concerned, it would require less time and effort to install string inverters compared to micro-inverters because of the large number of micro-inverters compared to the string inverters.
As far as the performance of these inverters in rooftop solar installations as regards outside temperature is concerned, there are some misconceptions we would like to clear. So the misconception that micro-inverters don’t perform as well as string inverters in hot climates is generally propagated by rooftop solar PV installers out of ignorance or lack of experience using micro-inverters such as the ENPHASE M215, M250, or S280, and it really can’t be further from the truth. In fact, there are numerous studies out there to prove this.
First of all, Enphase micro-inverters operate at a standard 120/240 volt rate and only produce up to 1.13 Amps per each unit, which actually keeps them cooler than string inverters. On rooftop solar installations, the micro-inverters are either attached to the solar modules or mounted on the roof alongside the solar modules. However, they are installed in the shade of each module and typically operate at 20ËšF cooler than the surface of the modules. There is also significant airflow around each micro, which help them to maintain cooler operating temperatures. String inverters operate at higher amperages and voltages (up to 1000 Volts DC) and therefore create a lot more internal heat than a micro-inverter because they process a lot more power. They also typically do not have any internal cooling fans, some manufacturer’s models do, and they rely on the heat sinks to dissipate heat and by way of cutting back on their production output – meaning cutting back on the amount of electricity they produce to stay within their set operating temperatures.
Enphase micro-inverters record their internal temperatures, along with other data, and store the information on the Enphase Enlighten monitoring platform. The internal temperature is measured inside the sealed micro-inverter. According to reports of this data, Enphase micro-inverters installed in rooftop solar installations even in the hottest locations in the United States have never exceeded the maximum allowable internal temperature within their lifetimes and contrary to popular belief, do not have higher failure rates than micro-inverters in more temperate environments. A recent study of internal temperature data from 75,000 Enphase Microinverters in five of the hottest locations in the US found that, where some microinverters were operating near the upper-temperature limit, others in similar heat in nearby installations were reporting 50% cooler readings. This difference in internal temperature readings for the same product indicates that installation practices may have had an effect. Inadequate or incorrect installation procedures were used by those installers that may have seen failures of the Enphase product due to heat.
Ultimately, the use of Enphase Microinverters on solar arrays in hot climates (or really any climate!) will provide homeowners and solar installers with better performance and longer life. Not only is the failure rate minimal, but if an Enphase Microinverter does go down, you and your Rooftop Solar installer are immediately notified of any problem by the included Enphase MyEnlighten monitoring system, and troubleshooting can begin immediately. This ensures that you are not without solar PV power production for months or more while you sift through your electricity bills to see inconsistencies. The other advantage is that if a Micro-Inverter does go down, then only a portion of your PV system loses productivity, whereas if your string inverter goes down, the entire rooftop solar PV system produces no power until the inverter is repaired or replaced. It’s no wonder why Enphase Microinverters come standard with a 25-year warranty, as opposed to a standard 10-year warranty on typical string inverters.
Are you considering making the switch to rooftop solar at your home? Get a free quote here, and we’ll provide you a custom rooftop solar proposal to best suit your family’s needs.