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In Chapter 2 we described the difference in DC:AC ratios between microinverters and string inverters, even when batteries aren’t used. This bonus chapter goes into the details of why and how string inverters outperform microinverters.
The DC:AC ratio is a key metric in solar design. It compares the total power capacity of your solar modules (DC) to the maximum output capacity of your inverter (AC). For example, a 15kW system with an 11.4kW inverter (or sum of microinverter capacity) has a DC:AC ratio of 1.3:1.
According to Aurora Solar, a leading solar design and performance simulation software, “It often makes sense to oversize a solar array, such that the DC-to-AC ratio is greater than 1. This allows for a greater energy harvest when production is below the inverter’s rating, which it typically is for most of the day.”
However, Aurora Solar continues, “this approach is not without costs. Either spend money on an additional inverter or lose energy harvest to inverter clipping.”
But not all DC:AC ratios behave the same, especially when comparing string inverters and microinverters.
While both string inverters and microinverters clip energy when module output exceeds inverter capacity, string inverters will clip less on average because:
1. Aggregate Power Smoothing in String Inverters
String inverters manage power at the array level, combining the output of all modules into a single DC input. This means:
2. Per-Module Clipping in Microinverters
Microinverters operate independently for each module, converting DC to AC at the module level, creating inefficiencies:
Let’s see the difference by comparing the performance of microinverters vs. string inverters with the same DC:AC ratio on the same house (see Figure 16) with the following features:
Below we can see the performance comparison between these two configurations. The microinverters in Option 2 clip 13% of the production because they clip at the module level. The string inverter in Option 1 doesn’t clip because the lower output in the East array balances out the higher output of the West array.
The power production curves in Figure 16 illustrate the difference in performance between the two technologies over the course of a single day.
DC Architecture: Will only clip if TOTAL POWER OUTPUT (EAST + WEST arrays) exceeds inverter capacity. With different orientations. Clipping is less likely.
AC Architecture: Clips at each module – so first the EAST then the WEST arrays are clipped, reducing TOTAL POWER OUTPUT. Clipping is more likely.
Modules are frequently installed across multiple orientations (e.g., east- and west-facing roofs) because:
Not all DC:AC ratios are created equal. While both string inverters and microinverters clip energy when DC power exceeds AC capacity, string inverters significantly reduce clipping losses by aggregating power across the entire array.
For homeowners looking to maximize their energy production and savings, a DC-optimized string inverter system is the clear choice—capturing more energy, minimizing losses, and preparing for the future of solar + storage.
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Séminaire en ligne : Le 15 avril (jour de l'impôt aux États-Unis), nous organisons un séminaire en ligne qui abordera les détails de la série de taxes sur les micro-onduleurs. Inscrivez-vous au webinaire ici.
Vous trouverez ci-dessous la liste complète des chapitres inclus dans cette série (des liens seront ajoutés au fur et à mesure de la publication des chapitres) :
Vous trouverez ci-dessous la liste complète des chapitres inclus dans cette série (des liens seront ajoutés au fur et à mesure de la publication des chapitres) :
