Sol Ark 15 != Deye 16K, you got your facts wrong. Check the specs. The Sol-Ark 15K will only output 12KW on the LOAD output (UPS/Battery), while the Deye is 16KW.
This my 16K OFF-GRID, the LOAD in this stress test were generated by the following.
1. L1 + L2 Level 2 EV charging on 240V
2. L1...