Micro inverter vs String inverter

The real world is a far different animal. In the real-world environment, modules are partially shaded, facing in different directions, they soil at slightly different rates and by different means, leaves fall on them, etc. All these elements affect a string inverter system much greater than they do a micro inverter system. The argument for micro inverters is that the mitigation of these effects will result in them out performing the string inverter. This argument is furthered by the AC Module which now makes the installation of micro inverters more competitive than the field installed version. As far as the wattage and cost issue is concerned, micro inverters are now in the 250 watt range and they are used with solar modules in the 250-280 watt range so the more accurate comparison is 40 micro inverters compared to a 10 kW inverter (roughly). The answer is that the micro inverters are about $1500 more expensive in this example but take about $500 less to install when in AC Modules (NOT field installed) and offer better value in energy produced to the customer for the reasons stated above, and provide better monitoring. Additionally, if any one component fails, you only loose that one module.

The AC Module does not have a field installed micro inverter. The AC Module contains a FACTORY INSTALLED micro inverter which eliminates the need to install a micro inverter in the field. This is a significant savings. These AC Modules do NOT require a separate trunk cable. They also are not subject to the grounding requirements of NEC 690.47 which is a significant time and material savings. If any one component fails, you only loose that one module, but, if the string inverter fails, you lose everything. Nothing's perfect. The market has spoken and the trend is to choose the micro inverter. That trend is only going to be accelerated with AC Modules.

I've been in the solar business for almost 30 years. I've installed countless systems with my own two hands so I understand being "in the field." The warranty issue has been carefully thought out. The AC Module is warranted as one product and will be replaced as one product by the panel manufacturer. The other warranty issues you raise apply equally to a string inverter. The answer, as with any product, is to buy from a reputable manufacturer.