How many wheels can you actually fill?
Studios usually buy another wheel when the real bottleneck is somewhere else entirely. Here is how to find out which constraint is binding.
Four constraints, and only one of them is binding
Wheels, kiln throughput, instructor hours and demand. Your capacity is whichever runs out first, and it is very often not the wheels.
Kiln throughput is the one people forget
Every student produces two to three pieces per class, and every piece needs a bisque firing and a glaze firing. A single kiln doing two firings a week has a hard ceiling on how many pieces can pass through it, whatever the wheel room can seat.
If pieces are waiting two weeks for a shelf, another wheel makes the queue longer, not the revenue larger.
Instructor hours are usually the real limit
One person can teach perhaps 20 to 25 contact hours a week before quality drops and admin stops getting done. At three-hour classes that is seven or eight classes — and if your room seats six, that is your ceiling regardless of how many wheels you own.
Measure before you buy
Track the fill rate of the classes you already run. If beginner wheel throwing is selling out in a day and handbuilding is running at 40%, the answer is more of one class, not more equipment.
Buy the wheel when your best-selling class is consistently full AND the kiln can absorb the extra pieces AND somebody is free to teach.