Am I really being Net Metered?

Perhaps I'm just being paranoid, but how do I know that the power I am sending back through my utility meter is actually offsetting my usage?  I have a Wind/Solar hybrid system and quite often the usage indicator on my utility meter (read Speedometer) will run backwards as I produce more power than I use.  However, this condition never lasts long enough for me to see the actual "Billing" dials (read odometer)go in reverse. I know I could add another meter so I can track this net usage myself, but in the interest of simplicity does someone know enough about utility meters that they can assure me that if the wheel goes backward than so too will the Kwh dials.