Knowledge graph
Google's store of things and the relationships between them. Being in it is checkable; getting into it is not a purchase.
Checkable · the test is below
What it means
A structured record of entities and how they connect. A business in it has an identity a machine can reference rather than infer from scratch each time.
Why it matters for an HVAC company
It is the difference between a system knowing your company exists and working it out from scattered mentions. Local trades are under-represented, which is both the problem and the opportunity.
What would settle it
Search your business name. A knowledge panel appearing is the visible sign. For a definitive answer, query the Knowledge Graph API for your name and see whether an entity comes back.
A worked example
A contractor with 340 reviews and eleven years of trading returns no panel. Their competitor with 90 reviews does, because that competitor's name, address and category agree across their site, their profile, two trade bodies and a supplier listing. Nothing was bought.
The limit on that
No agency can add you to it directly and any offer to do so should be read carefully. What they can do is make the underlying records consistent.