In recent weeks we have seen an increased interest among our customers in micro-inverters. Micro-inverters are similar to conventional inverters in that they turn the DC solar power produced by the solar module into AC power which can be used in the home and fed into the utility grid. However, micro inverters are different than conventional inverters in that one micro-inverter is attached to each solar module at the back of the module whereas conventional inverters, a.k.a. string inverters, are mounted at ground level, typically in the garage of a home and a single inverter will convert power for about 30 solar modules. So for a typical home that uses micro-inverters, 30 micro-inverters would be mounted at roof level under the solar array.
Many people believe micro-inverters are new, cutting-edge technology. They are not. Micro-inverter technology goes as far back as the 1980s. The manufacturers of micro-inverters consistently have gone into business and then after several years they are out of business or bought out by larger firms.
The promise of micro-inverters is that since there is a single inverter per solar module, the system, as a whole will perform better. The proponents of micro-inverters argue that conditions which reduce system performance such as shading, soiling and differences in electrical characteristics amongst solar modules are mitigated or minimized because only the solar module with such a condition will be impacted and all the other modules will operate at their optimal efficiency resulting in an increase in overall energy production. Mind you, I said the "promise" of micro-inverters...
Here is the reality; micro-inverters do not, based on actual real world data compiled across dozens of systems, offer a calculable increase in energy harvest over conventional string inverters. However, in rare instances, micro-inverters are a preferred option over a string-inverter such as when the roof space of the home has multiple different orientations and a single inverter's MPPT tracker will not work, or when a system is subjected to substantial shading. Otherwise, it is the opinion of this author that micro-inverters are to be avoided.
Of the several dozen systems we have installed with micro-inverters, at the request of the customer, ALL have had inverter failures. This makes sense and why we were reluctant to adopt the technology for all customers. Think about it, micro-inverters are electronic devices and they are mounted on the back of a solar module where temperatures exceed 150 degrees. Electronics and heat are not friends. Now, when a micro-inverter fails, it is not an easy fix. Technicians have to get on the roof, rip out the entire array to get to the failed inverter under the array, install the new micro-inverter (God help them) and re-install the system. Does this sound like a good idea?
It is disconcerting to see that several of our competitors have gone to offering micro-inverters standard. In about 2 years they will spend the majority of their time doing service calls to failed systems. This will likely result in their demise as businesses and we will then have to service these orphaned systems. Fine by me, but definitely not good for the local industry as a whole.
If you are a homeowner looking to go solar do not get micro-inverters. You will regret it.