Usage depleted overnight. All updates set during free time.

I posted the above comment and immediately used another 1%

Sat down to check data usage at 1:30, meter said 85%.  I turned wifi off on my phone ( I'm testing everything) it had been on all day.  Within 30 seconds my meter dropped to 52%.  and within the next few minutes to 47%.  I walked away for about 10 minutes, came back to 45%.  I know that I did not use that much data!

and another 1% for that comment!!

Left the computer and came back at 3:05 pm data dropped another 1%. Checked email 4 times and got error messages that it could not connect to hughsnet server. Data dropped from 42% to 39% and I didn't even get my mail.  Ok, Hughesnet, whats next? Frustration is setting in!

In the last 2 minutes I dropped to 38% by signing into Facebook and no the videos do not automatically play.  Was on just for a quick check and signed out.  Now data is 38%

I dont think it should drop that fast either based on what little you were doing, you mentioned that you have a Iphone, what model? the reason I ask is because the IOS 8.0.0 - 8.0.1 had issues with wifi connections and can cause data lose due to retrying to connect, keep in mind im just guessing here. what I would suggest next is to only connect 1 computer to your router and do some browsing and see if your data seems to be dropping at what you would call a normal level, if 1 computer does ok then add the other one and see, if its ok with the 2nd computer then add your other computers or devices 1 at a time until you start seeing the data dropping at that point remove the devices 1 at a time in reverse order to see if the drop stops. another option is to download a program Net Guard here is a link to it and its free. you will need to install it on all computers you connect to your router and it will tell you what programs are using data and how much. unfortunately Im not familiar with this software but there are a couple of other customers on here that know it very well, they are Gwalk900 and sgoshe they can help you understand how to read it.
 http://www.cucusoft.com/netguard.aspx

it really sounds like you have some one else on your network you dont know about. Im not familiar with netgear routers, does it have the ability to log data usage by ip address? and can you log in to the router and see all wireless connected devices?

Unplugged the router at about 3:30 and plugged it back up at about 6:30.  Usage started dropping by 1% while browsing the web.  I think it was probably a little fast, but nothing I can say for sure.  It just seems that there was a time that I could look at every page I wanted to and use 5% maybe.  Of course I think the internet was to slow, but thats a whole different story.  We have not updated our phones to the 8.  My husbands phone has no apps other than the ones that came with the phone.  He has been on wi fi from day one for 10 months. It is a work phone and has to stay connected.  We have never had a problem with it draining our data.  When I turn the wifi off on my phone and watch my cell data it does not use that much.  It has used 176 MB in 3 weeks and that is using extra apps that I have downloaded.  They are not set to update anything without permission.  I'll try to check the log data on the router today.  

Lea what web browser do you use? if it Chrome install ad blocker pro its free and will block a lot of unwanted data drain

recall apple updates are not "controlled" (at least from what I can tell), they just happen.  If there is a way to control when the apps/ ios is updated, would be nice to know about.  Good luck. Also: if you have Amazon pads, they are even worse about uncontrolled downloads and worse, if you watch a video on them from prime, it sets the HIGHEST download possible, and cannot be controlled like in Netflix.