String Inverter or Micro Inverter: What to Choose?
by Fabien Prevost
The heart of each photovoltaic installation contains a photovoltaic inverter. It will transform the energy collected by the solar panels into usable electricity. However, there are two main categories of inverters whose differences are little known: string inverters and micro-inverters.
In order to help you understand and choose your equipment well, we are studying here the major differences, advantages and disadvantages of both types of equipment.
In the case of a solar system connected to the grid, the string inverter is connected at the end of series of solar panels. There is only one inverter for all the panels.
The advantage: the price. This type of system with a single inverter limits the overall investment cost compared to a system equipped with a micro-inverter for every panels.
This is the most suited system for most well exposed roofs.
The downside: It's production. The string inverter does not produce less, but in the event of a panel failure or shading event, the entire string of panels suffers in output. Indeed, the serial connection reflects the possible technical failure of a panel on the other panels of the same chain. So if any panel in the string is adversely impacted that no longer produces full capacity or zero, the whole string Is impacted. By example, the final consumption of the kit of 10 solar panels (in a string) may therefore be only 10% of its capacities here, i.e. a loss of 90% of production.
In the case of a solar system equipped with micro-inverters, each panel is connected to one micro-inverter. There are therefore several micro-inverters. The panels are no longer connected in series the micro-inverters are connected in parallel. Each panel being connected to its own micro-inverter.
The advantage: Guaranteed and optimised production. In fact, in the event of a panel failure, the other panels always produce optimally. Having electricity distributed between each panel or pair of panels ensures optimal production of the entire system. By example, the final consumption of the kit of 10 solar panels can therefore be ensured here at 90% of its capacity, e.g. a loss of 10% of production. Panel level monitoring on an individual basis also ensures early fault detection.
In addition, micro-inverters are recommended for small installations because the least powerful string inverters generally start from 1500 W (6 panels). Micro-inverters also allow an easy upgrade of your system, indeed, micro-inverters allow you to add panels to your installation at any time, without having to re-string the whole system.
The downside: the price, because there are more inverters compared to the string inverter system and micro-inverter technology is also more advanced, the price is felt.
It's up to you to choose your formula with these elements in mind. Price should not be the only factor. Think long term!