Featured snippet
The boxed answer Google has shown above results for years. It predates all of this and is constantly sold as part of it.
Checkable · the test is below
What it means
A snippet lifts text verbatim from a ranking page and shows it in a box. It is extractive: the words are yours, unchanged. That makes it a different thing from an AI Overview, which writes new text from several sources.
Why it matters for an HVAC company
Because agencies bundle snippet work into answer-engine proposals, and it is older, better understood work with a clearer mechanism. That is not a criticism, but you should know which part of the quote is 2016 practice.
What would settle it
Search the query and look. The box is either there or it is not, and if it is, the text is either yours or somebody else's. Stamp the query, device and location.
A worked example
"How long does a furnace last" returns a snippet quoting a manufacturer's page verbatim. The same query returns an AI Overview composed from five sources. Winning the first has no bearing on appearing in the second.
The limit on that
Holding a featured snippet does not make you more likely to be cited in an AI Overview. They are separate systems and the overlap is not established.