I've heard some claims that the zero export feature on inverters, like the Enphase system, isn't actually perfect and can allow for some minor power leakage. Does anyone know if this is the case for Enphase, which is quite popular in the U.S.?
2 Answers
Most zero export systems don't actually optimize that well across both phases. For instance, if your home is using 2000W, the solar system might just spread that output evenly across the phases. So even if you're using 1200W on one phase and 800W on another, it will produce 1000W on each phase. This results in a bit of export on one phase while importing from the grid on the other. In the example given, you could see about 200W being imported on one phase and 200W exported on the other.
What if I used two single-phase inverters instead? Would that allow for better control of the zero export?
Yeah, there is usually a small amount of leakage. When you set it up, you can choose a tolerance for how long the system can go above the limit before adjusting to stay below it.
We do have three-phase systems that can manage asymmetric loads, but there's still a bit of lag time. Anytime your energy use changes, there might be a brief moment when power flows incorrectly.