they called but said nothing & then hung up

"Welmy" identified himself from Bright Energy Network and said he would provide a free energy analysis of my home.  He said they get paid by the government and are not selling anything. "Louis" came on the line to confirm my appointment and gave me a confirmation number. They gave me this phone number as a call back number, but when I called this number it goes directly to voicemail. What kind of scam are they running? I am now frightened about how I am going to be manipulated.

You're so right.  It is a scam.  They "pretend" to give you an energy audit which is really just a way to get people to your home to try and sell you this absurd solar unit that will "run your grill" and cook your food.  I answered the call today because I  had my call blocker turned off as I was expecting a call from a company that might use a different number than the 1-800 that I called them from.  Some guy (heavy Indian accent) said "I need to speak to the home owner because you qualify for a free government sponsored energy audit."  I said, "yeah right, so you can sell me some piece of solar crap that doesn't do anything that a hot rock won't do."  He said, "no mam our units will cook all of your food and you will save money."  I told him he could save money by not calling me anymore.