I was looking at our PoE switches the other day and noticed that our PoE VOIP phones (Avaya one-X Deskphone 1616s) are using between 2.5 and 5.5 Watts of electricity with an average of 4.68 Watts for the 25 phone sample. This is the average with no one on the phones. Seems high but we are really not talking about a lot of money, here are my calculations:
4.68 X 25 = 117 / 1000 = .117 X 24 = 2.808 X 365 = 1,024.92 kWh per year
In Hawaii at 20.8 cents per kWh, the cost is $213.18 per year. In Massachusetts at 18.17 cents, the cost is $186.23 per year. In Utah at 7.07 cents, the cost is $72.46 per year. In the U.S. on average at 10.3 cents, the cost is $105.57 per year.
Also, you have to figure that even with a traditional PBX the phone draws some power. Here is where it gets difficult. I could find data for analog phones easy enough. Analog phones draw around 5 mA when on-hook and around 21 mA when off-hook with a maximum of around 120 mA at around 48 VDC. However, most PBX systems now use digital telephone sets, and finding out any electrical information on these types of phones proved extremely difficult.
I searched online and I called a couple of phone manufacturers, but I still could not get a definitive answer. I am guessing that the newer digital sets with larger LCD displays draw more power, but I am going to make a huge assumption here until I can actually test a digital phone and say that the older digital phones probably draw about the same amount of power as analog phones. I am hoping that since the phones probably do not draw much power while on-hook that I am not underestimating on these older digital phones with limited or no displays. As soon as I can get my hands on a digital telephone, I plan to test it out. Please comment if you have any information. So, here is the calculation:
Assuming 2 hour average talk time per phone per day
.005 X 48 = .24 X 25 = 6 / 1000 = .006 X 22 = .132 X 365 = 48.18 kWh per year
.021 X 48 = 1.008 X 25 = 25.2 / 1000 = .0252 X 2 = .0504 X 365 = 18.4 kWh per year
(There would be a difference for the ring cycle on analog lines and maybe on digital, but I don't think it would be significant in most environments)
Total = 66.58 kWh per year
So, in the U.S. on average you would be paying $6.86 per year to operate the 25 traditional phones. Therefore, the difference between VOIP and traditional for 25 phones is, on average, in the U.S., about $100 dollars a year. However, you can make it sound a lot more ominous by saying that by running VOIP phones you are emitting more than half a metric ton more Carbon Dioxide into the atmosphere every year.
Here are some other "Green" benefits of using traditional phones in place of VOIP that are harder to quantify:
Less networking equipment
Potentially less Air Conditioner usage
Ability to use older copper wiring and not have to replace it with Cat 5e (although you can argue that by placing the network switches closer to the edge you are reducing the amount of cable needed)
Traditional PBXs may end up in a dumpster if replaced
I realize that I have made many assumptions here. For example, a call center would have the phones off-hook at least 8 to 12 hours per day and possibly 24 hours per day. Also, for the most part, you can run more VOIP phones per physical PBX than analog/digital telephones. I am assuming you are running a PBX that supports at least 25 VOIP or traditional phones or that the PBXs have similar power requirements aside from the phones. In addition, I am assuming that most VOIP phones will have similar power requirements to the Avaya 1616. I am sure there are many more I have missed.
I have seen numbers floating around that say it is 30 to 40 percent less expensive to operate traditional phones than VOIP phones, but nobody had any data to back that up.
Hey, I am not saying don't buy a VOIP PBX. We have replaced our traditional PBXs. Who knows what the deal is with global warming anyway.