My biggest problem with any kind of consultant is their unwillingness to put their money where their mouth is...
They're quick to tell you you're going to save 10% on your electricity bill every month, for a small capital outlay of $10000 or $100000...
OK, sounds good, guarantee that. If we don't save 10% per month you refund us the capital outlay.
And they disappear like... I dunno... stuff that disappears ;-P