It sounds like the instantaneous hot water is the problem. They require high power for a short period of time. If a larger tank can be accommodated somewhere, the water can be heated more slowly at lower power – same energy over a longer time. Ideally, a heat pump hot water system with a decent sized tank would store hot water and it would require lower power still due to its intrinsic efficiency.
You might need to put two compressors outside on common property, one for the reverse cycle aircon (efficient electric heating) and one for the hot water system.