HVAC scam almost got me

I’m new to my neighborhood and still trying to figure out the local culture. So far I’ve only briefly met a few neighbors and they seem nice enough, but I don’t really know who they are or what to expect from them. I’m also not familiar with the dangers that reside in this area, for instance, if there are door to door scammers who drop by or not; I’m starting to suspect that yes, there are plenty of them. Just last week I had three different individuals stop by to inquire about my HVAC usage. I thought it was strange when the first person knocked on my door and asked to see my latest energy bill. I told her no, I wasn’t interested, and she then asked to see my furnace instead. She insisted that there were new energy efficient models out there and she could do a simple inspection to tell me what my other heating options were. I asked to see her credentials as an HVAC dealer or heating and cooling specialist, but she wasn’t able to provide me with any answers, so I turned her away. Over the next three days I had two additional salesmen stop by, also inquiring about my heating and cooling system. I denied every one of them from accessing my home, and it turns out that I did the right thing because there were a string of robberies all around the neighborhood the very next week. The victims all reported talking to some mysterious HVAC professionals shortly before the break ins.

HVAC unit