A Portable Power Station is an Off Grid System. When there is a power outage you have to disconnect your devices, e.g. computer or water pump from the grid and connect them to the Portable Power Station. This can be done manually or automatically by a separate switch.
More comfortable is using a Hybrid On and Off Grid Inverter which switches automatically within 20 ms or less. There are very flexible inverters which can be used off grid or on grid, with or without solar panel, with or without battery, with or without a generator or all together.
To cover power outages you can start with an inverter and a battery. The battery is charged from the grid. More batteries, solar panels or generator can be added later. Even more inverters can be added later.
See e.g.
Hybrid Solar On and Off Grid Inverter
POWMR