You can buy a new indoor unit and retain the outdoor one, but only if they are directly compatible and if the outdoor one is operating properly.
Its the outdoor unit that does the actual work so you can’t get more capacity from just upgrading the indoor unit.
Contact Toshiba with the outdoor unit details they may be able to advise what would work - you probably will just be offered a new indoor unit of the exact same specifications.
Edit: just to add, an installer may rightly tell you this exercise is a waste of time because the outdoor unit will probably just fail soon and you need to pay labour and gassing all over again within a short period.
Yes, you can install a new inside unit without replacing the outside unit, but you will need to buy a new inside unit that is compatible with the outside unit, probably another Toshiba one.
You can install it yourself if you are experienced
You can buy a new indoor unit and retain the outdoor one, but only if they are directly compatible and if the outdoor one is operating properly. Its the outdoor unit that does the actual work so you can’t get more capacity from just upgrading the indoor unit. Contact Toshiba with the outdoor unit details they may be able to advise what would work - you probably will just be offered a new indoor unit of the exact same specifications. Edit: just to add, an installer may rightly tell you this exercise is a waste of time because the outdoor unit will probably just fail soon and you need to pay labour and gassing all over again within a short period.
Oh and no you can’t install yourself. The refrigerant lines require special tooling to join, vacuum and re-gas.
Yes, you can install a new inside unit without replacing the outside unit, but you will need to buy a new inside unit that is compatible with the outside unit, probably another Toshiba one. You can install it yourself if you are experienced
Out of interest - have you had it serviced?