They hang up every time I answer.

Same here!

If you call back, it says to leave a message.

Just got a call a couple of minutes ago. They call all day and night and never say anything.

They call all day every day and never say anything WTF!

Scam call from USA Energy Group, they claim to be a non-for profit organization that is looking to help save the environment and natural resources one household at a time.  Just let a complete STRANGER into your house and see if you qualify for a government cash grant of $4,000.00.  Give me a break.  They couldn't address where this money was coming from, what their inspection entailed or give me any details about their company: location, website, etc.  SCAM, BEWARE!!!!