[NathanKP]

It's not just the HVAC system itself, it is the supply chain to operate the HVAC as well. There is waste heat from the power transmission system to get power to the HVAC unit, waste heat from the power plant that produced the power, waste heat from the transport of raw materials to the power plant, increased global warming heat from the CO2 that the power plant produces while burning those raw materials, etc.

Obviously this can be mitigated if you are able to get renewable power from a nearby source like a geothermal plant, hydroelectric, or solar. But if you are using fossil fuel power from a long distance away, that means any unit of heat moved by an HVAC involved many units of heat production to ultimately move that unit of heat.