How do you know WHEN your business actually needs another technician? (heavy emphasis on "actually")

When your HVAC company is slammed and customers are waiting longer than they should, the obvious answer seems to be "we need more technicians".

But I wonder how often that's actually the right answer. A company can be busy because it genuinely doesn't have enough capacity. But it can also be busy because of scheduling, geography, callbacks, uneven demand throughout the day, certain techs being overloaded while others aren't, jobs taking longer than expected, etc.

Adding another technician obviously isn't free. You're adding wages, truck costs, insurance, training, tools, management overhead, etc. So if the underlying problem is utilization rather than capacity, one may just be adding another expensive person to the same system.

I'm curious how experienced owners/operators actually make this decision. What numbers or signals do you look at before deciding "we need another tech"?

Is it something like revenue per truck hour, utilization, booked hours vs available hours, callback rates, lead times, overtime, geographic spread or is it mostly gut feel from being in the business?

I'm not an HVAC operator, so I may be looking at this completely wrong. That's actually what I'm trying to figure out.

Would be interested to hear how you guys think about it