whats the experience pay for HVAC

Depends on the local area market and the state. Is the local area market flooded with large HVAC companies? Do you want to own your own business? Do you want to work for a larger facility management firm and work in one of their publicly leased buildings? Do you want to work for the Federal government with GSA?

In Virginia around the Tidewater region, there are quite a few HVAC large and small companies. That said, they (a certified HVAC employee) can earn anywhere from $17-32 an hour. Depends on their experience, availability, and supervisory level. I was the operational director of a state managed museum and we paid our HVAC employees anywhere between $32-52k for our full-time staff (benefits included). However, when I worked in DC, the facility management group I worked with (their building housed the theater I worked for) paid their HVAC staff anywhere between $55-100k. This was due to the senior supervisor managing multiple buildings and overseeing the HVAC staff in each of those facilities. I'm not sure what the Federal government would pay, but I'm sure a quick search on usajobs.gov would solve that mystery.

I used to hire inspectors nationwide to take pictures and complete reports on residential and business properties and some of those inspectors would be HVAC certified. So clearly, some HVAC folks find it easy to get a side hustle when business is slow. My friend's son who is in his late 30's recently was certified in HVAC; I think he started out at $15 per hour while he was working towards his certification. This also meant he got valuable on the job training.