Dave needs to upgrade his 3kW home solar system, what are the options?
why not have two strings of panels . one for on-grid, your power retailer. the other string for off grid.
have one solar power system that is independent, uses off grid off grid deep cycle Lead-Acid batteries to store electricity for independent home use.
have two sets of power outlets in some rooms. so electricity demand is from two systems.
two inverters.
example 500w AC single-phase off grid power outlets. all other power outlets on-grid.
or sets of lights off grid. choose if electricity power outlet is on-grid or off grid.
one inverter can be switched off if no off grid AC is needed.
most if not all Hospitals have two independent systems on-grid or off grid uninterruptible.
you can have off grid to power star trek sliding doors or strip lights.
a family member of mine is building an earthship thing! star trek house.