Updated: Jan 16
Every power system has a peak power rating which cannot be exceeded without risking damage to either the appliances that use the system or the batteries and the inverter. Since overloading is a major concern for the health of a power system and since most if not all users, use their systems as UPS, that is, on auto-mode, all inverters come with circuits that protect them from overload. Most inverters are built to either ring out an alarm or automatically shut down if they are overloaded otherwise the inverter will be permanently damaged and major financial strains will be placed on the user.
When a new appliance is to be added to a solar and/or inverter-battery power system, it will most definitely raise concerns about expanding or upgrading the system to accommodate the new appliance.
There are no 'upgradable inverters' as it were. The reason is because most systems have to be tailor-made for the power peculiar needs of each user and also for flexibility in costs. In most cases, the standard installation practice is to have the different components of a solar power system acquired separately and then installed together.
Expanding a power system may require either of the two:
The purchase and installation of entirely new components,
Or the upgrade of some parts of the system.
Battery power can be expanded with the addition of a new cell. Solar output can also be expanded with the addition of new solar panels.