I've heard a lot of back and forth on this topic, and it seems using ESS to feed back anything to the grid certainly does require a valid grid code selection, and is technically not legal in the US therefore.
What I am trying to find out now, is if the use of ESS for peak-shaving only is permitted, without any grid feed-in, and no PV connected on the AC-Out side of the MultiPlus. This forum here discuses the topic at length, and read some people claim that yes ESS can be used as long as there is no feed-in happening, but wanted to get some sort of official clarification from someone who is licensed here in the US maybe and has done such an install:
In the state I am looking at having this installed (Oahu), electricity can be billed based on the time of day, costing as much as $0.52/kwh at night, and as little as $0.25 or so during the daytime, due to the excess of clean solar, and high cost of importing fuel to burn in power plants. Furthermore, I am living in an apartment-style condo where I do not own the roof above me, and cannot install any solar of my own.
In my scenario, ESS would be used to power the loads on the AC-Out side during the night time, and recharge from the grid connected to the AC-Input side during daytime. The batteries would never be discharged back to the grid, as I would not be credited for this anyhow. However, I have read that when the MultiPlus is inverting, powering a heavy load like an electric water heater - the load which would shut off abruptly at times, causing a small amount of energy to possibly be sent back out the AC-Input side, if even for a few milliseconds. Would this not then cause the installation to be illegal due to the lack of grid code compliance in the US?
