Sunday, October 3, 2010

Power consumption and Cost saving of Using Ooma

Devices measured:

  1. Ooma hub
  2. Linksys WRT54g wireless router
  3. Traditional wired phoneset connected to Ooma

Power-meter: Kill-A-Watt EZ


  • System idle: 27 watt
  • Phone is off hook (dial tone): 30 Watt
  • Phone is dialing: 30 Watt
  • During talk: 30 Watt
  • Check voice mail tru the hub: 28 Watt

How much the electricity cost we pay monthly?
For Northern California, PGE has a chart describing the rate.  The average KWH rate for residential seasonal schedule E-8 is $0.22832 (this is just an average, the actual calculation depends on the tier/how much we consume electricity above its baseline).  So, the maximum KWH for Oma in a day is: 30 Watt * 24 hours = 720 WH = 0.72 KWH.  In a month (30 days) = 21.6 KWH or it costs = $4.32

If we don't subscribe to Ooma premier service, there is no additional cost, so it is the actual monthly cost we pay.  If we subscribe to annual Ooma premier service which $119.99/year, we end up paying: $119.99/12 + $4.32 =  $14.32 (rounded up) per month.

As a comparison, when I subscribed to AT&T landline local service (local unlimited), I paid (total, including all the fees and taxes) $27.15.  This did not include caller-ID and all other features.  It was just bare minimum.  With Ooma premier, besides we get caller-ID, we also get two lines, call forwarding (or simultaneous ringing to another number), broadband voice mail (with MP3 file can be sent to email we specified), and other features.  AT&T could have charged those features for additional $15 or more.

Now, how much we save by using Ooma?  OK, first we need to take to the account the broadband portion used for Ooma.  For example, I pay AT&T U-Verse 10 Mbps/1 Mbps (downstream/upstream) $45 a month.  In average, Ooma uses a fractional bandwidth, which is about 256 Kbps.  The max fraction of cost (hypothetically) is then = 0.256/10 * $45/month = $1.152, or about $1.2/month.  Assume we use Ooma premier, the total monthly cost is then $14.32 + 1.2 = $15.52/month.  The saving is = $27.15 - $15.52 =  $11.63/month.

The price of Ooma hub (including one Ooma scout) is $219.99 (at +sales tax (which is 9.25% in my area) or $240.34.  The number of months to recover the cost using the amount of money we save above is then $240.34/$11.63 = 20.66 months, or say 21 months (1.75 years).  After that, the saving we collect is going to our pocket.  If you decide not to use Ooma more than 1.75 years, you won't save any.

Note: the calculation above does not include power consumption of Ooma scout, but I surely is smaller than the hub's.

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