Home energy use

I did some calculations on the energy use in my house which I share with two other people. Our energy expenditure is a bit too high to my taste. Partly it has to do with the old house whose insulation may be lacking. The outdoor AC unit is probably operating inefficiently because of old age. The service person said its coils and fins are clogged with dust and dirt. The landlord does not seem too enthusiastic about cleaning or replacing it as it technically works. But in peak summer it kind of works all the time and still struggles to bring the inside temperature around 75F. I did my best to seal any leakage through the door and window edges.

Our utilities charges from 2009 Sep to 2010 Sep are respectively as follows:

$ 153, 153, 339, 333, 288, 381, 171, 150, 330, 375, 366, 450 .
That would make average cost $290. Per head $97 .

You see we are not the greenest people around. I really wish we didn't use this much energy.

I couldn't do much about the AC . The housemate upstairs is very sensitive about heat.
I am trying to employ a space heater for my room in the winter to see if I can save on the gas for heating. I am more sensitive to cold in the winter than heat in the summer.

I find that the highest gas bill in the winter was $239 and the lowest gas bill in the summer was $35. So the difference I assume is roughly from the centralised heating in the winter and that is roughly $200.

The highest electricity bill in the summer cost $339 and the lowest electricity bill in the winter cost $89 . I assume the difference roughly came from the AC in the summer and that is $250.

The electricity costs more than the gas in our house, though the costs are comparable. By using a space heater I am trying to trade electricity for gas, though hopefully more efficiently.

The electricity costs roughly 18 cents/KWh in a month in which the electricity bill is $178 which is kind of our average bill.
That mean if I can get by with the space heater which is rated 1.5KW on for 5hrs / day it would cost $40 . If it leads to only 50% usage of the centralised gas heating its cost will be down by 50% that is $100. The overall saving in that case will be $60. Not bad. Also, it may be warmer in my room this winter.

By the way the heater I purchased is Honeywell Electronic Ceramic Heater from target. There was only a store model left which I purchased for a 15% discount at a price of $23 .
http://www.amazon.com/Honeywell-Electronic-Ceramic-Heater/dp/B000TGX58E
I am happy with this heater. It is not the quietest thing. I wouldn't be making any audio recording with this thing on. It has a little more sound than the a fan. It doesn't bother me much.

Clear iSpot experiment

I ordered the Clear iSpot taking advantage of their promo offer. I wanted to check out the wimax/4G. Since the iSpot offer is affordable and contract-free I could not resist.

I received it the next day after I ordered. That was shipped to DC by UPS next day air from Las Vegas. After opening the box it took only a few minutes to put the battery in and see that I only have a week signal (signal indicator red) in my room.

Getting online was a bit more involved as I do not own any apple devices and iSpot is restricted by Clear to work only with apple devices. It was reported that they use mac address to identify and filter out non-apple devices. It is supposed to be easy to spoof a mac address with linux.
I tried the command to set the MAC address where x's are replaced by some hex digits (0-9 or A-F) and eth1 is my wifi interface. (I use ubuntu linux which has the command macchanger available from apt-get)

sudo ifconfig eth1 down
sudo macchanger -m 00:1D:4F:xx:xx:xx eth1
sudo ifconfig eth1 up

Unfortunately my computer and laptop have broadcom wifi and apparently their driver has some problem. After I changed the MAC address they will no longer associate with any wifi including mine. Upon searching the web I saw other people complaining the same.
Luckily I had a usb wifi adapter (Alfa awus036h) which uses realtek 8187L wifi.
Even that was having some difficulty associating after the MAC address was changed.
Finally I added the command to /etc/rc.local and restarted the machine and then it worked.

I was online soon after I entered the wpa password given on the label underneath the iSpot.
The configuration page located at 192.168.1.1 showed that my wimax signal strength was -80 to -82 dBm . A speed test using speedtest.net showed that I get around 2Mb/s download and 0.5 Mb/s upload . There was significant delay for the websites to start loading which I narrowed down to the delay in dns resolution. It was later fixed by removing their dns servers from the dhcp and statically assigning 192.168.1.1 as the dns server in the network-manager. After this the delay was absent. May be I could have used some other free dns server.

Now I tried to see if there was stronger signal available elsewhere in the house. I saw that in the living room near the window I get moderate strength signal (indicator yellow) and the signal strength is -72dBm and SNR around 21 ( RSSI:-72 , CINR:21 ). The speed test was showing consistently above 5Mb/s and, above 0.5 Mb/s upload. Speed was on the average 6Mb/s download and 0.75 Mb/s upload. Sometimes I saw download as high as 7Mb/s. So their claim of 6Mb/s download and 1Mb/s upload is reasonable.

Further tests to see the signal strength outside was hampered by the wifi signal getting weak and causing the wifi connection break. I later saw that the configuration page allows three different power levels for the wifi (short, medium and long) and the default is short.
I am yet to test outside with the highest wifi power level.

I also saw that when I put the iSpot inside the metal can of Pirouette (Pepperidge farm) with the side closer to the indicator lights facing the opening at a distance about 2 inches from it, and oriented the can towards a window the wimax signal strength improved by as much as 5 dB. One thing I later verified was that the wimax antenna on the iSpot is near the end closer to the indicator lights.

I am overall happy with the device. I have to find a way to change the MAC address of the broadcom wifi to be able to use with the laptop without using the external wifi adapter.


Inside the unit


Having seen that the device is working as expected, I decided to open it up and see the internals.
It uses the IC Atheros AR2317-AC1A may be for the wifi. The half elliptical shape antenna around the side close to the indicators. By touching it and seeing that the wimax signal strength goes down (I can't resist a hello to iphone 4 which has the antenna exposed and prone to touch) I presume that it is the wimax antenna.

I can see a miniature rf cable and connector which I guess is for the wifi antenna which I am not able to locate. Touching the connector causes decrease of the wifi signal strength reported by the wifi adapter. The wifi antenna may be on the underside of the pcb which I didn't remove to be able to see.

One can technically use the iSpot to serve any number of devices without spoofing the MAC address of each individual device. This can be done by using a wireless router like asus rt-n12 loaded with DD-WRT, configured as a client bridge whose wireless MAC address is suitably assigned to pass the check of the iSpot. Now the internet connection will be available at each of the ethernet ports of the client bridge. To one of those ports, if one so wishes, can a regular wifi router be attached to serve any wireless device without worrying about the MAC address restriction. iSpot sees only the MAC address of the DD-WRT client bridge.
But I want to mention that it may be against the terms and conditions of the service.

I believe that the iSpot is a rebranded imw-c600w manufactured by the company infomark ( http://www.infomark.co.kr/ ) .



A NOTE: The intent of this experiment is purely educational. I do not suggest anybody do this, nor do I imply the propriety or legality of it. If you use the iSpot service with unauthorized devices it may constitute a breach of the service agreement.


Also see:
http://www.zatznotfunny.com/2010-08/more-ispot-speeds-mac-spoofing/

Sometime back I sold the ispot on ebay.