Power for Z-wave thermostat

I have a GoControl GC-TBZ48 thermostat.
I would like to power it via a wall transformer due to the fact that I don’t have a C wire coming from my HVAC unit. I know that I need a 24VAC transformer. I need to know what the amperage range the transformer needs to be. I called 2Gig tech support and was told that the unit has to be powered by either a battery or a C wire. A customer service rep acted as a go-between with tech support so I was unable to have a discussion with a person that had the actual technical knowledge that I required.
Any help will be appreciated.

I would imagine a 24VAC 40VA transformer is enough since it is pretty common for Thermostats. You could get one on Amazon for around $20.

Thanks for the info. I need some clarification though. I am unfamiliar with the VA designation. I looked it up and see that it stands for volt amps. in determining the required current for a load I am familiar with amperage. So, I would think that 500 mah give or take might be the required current for my thermostat. I just don’t want to burn anything out so would appreciate some more guidance.
Thanks much

In DC circuit 1VA = 1W
It’s a little more complex due to the inductance and capacitance in an AC circuit so to be safe. Have it a little less than half. 1VA = 0.5 W.
That should be way more than enough for your thermostat.

mAh is refer to milliampere hour. It’s very common used for capacity of of a battery.

" Have it a little less than half. 1VA = 0.5 W. "

Less than half of what?