After receiving an electric bill that claimed I used more than four times more KWH of electricity in a 60-day billing period than had ever been used during a similar period in the four year history of my house, I am preparing to do battle with CFE, the Mexican national power company.

Since CFE does the proper (IMHO) thing by increasing the cost per KWH as the usage increases, this caused a truly staggering electric bill.

I only have four things in the house that use more than a few watts of power: My computer, SWMBO's computer, the TV set, and the refrigerator. Everything else is just light bulbs and stuff like the cable modem and telephone answering machine. Before I go storming in there, I want to be sure that it truly isn't possible that I could have used an average of 20 KWH per day.

I figure the refrigerator to be the largest user, at about 3--4 KWH per day.

Next would be my computer, usually on for about 15 hours per day. It is probably pretty power hungry, with four hard drives, a 22" LCD monitor, AMD dual-core processor at 3GHz, 2 GB RAM (recently upgraded to 4 GB), and audio and video on their own cards (i.e., not on the motherboard). There is a color laser printer that sits in standby mode (i.e., fuser not heated) 99.9% of the time.

SWMBO's computer is an iMac, sits in sleep mode about 20 hours per day, gets used about 4 hours.

The TV set is a Sharp LCD, 32", and is on for maybe three hours per week and is probably not a significant factor in overall usage.

I have been taking my own meter readings every morning for the past 10 days, and daily usage (according to the meter) is 5--7 KWH per day. This makes it hard for me to believe that I used 1200 KWH in the preceding 60 days. Apparently I am not alone in my complaint. There have been news stories about others besides myself suddenly hit with impossible electric bills, so possibly they have some problem with their billing software.

Can anyone hazard a guess as to what my power usage might be for the two computers?

tanstaafl.

If it's an aluminum and glass built iMac (instead of white plastic), Apple has full reports of typical power usage of the 2009-2010 models here:

http://www.apple.com/environment/reports/

With your computer being custom built, it's hard to say. The best way to monitor it would be something attached to the electrical feed to measure it there. Or, depending on the power supply, monitoring software may work to show the realtime usage there. My Mac Pro for example breaks down power usage by component and I can see this via a program (mac only) called iStat.

I am suspicious though of a claim of 1200KHW over 60 days (20 per day average) if your only seeing 5-7 a day by monitoring it recently. Thats more then double, and I'd imagine you didn't just recently decide to turn off a bunch of things.

What they do around here is to read the meter only every few months, then adjust the usage in that month. I wonder if that's what they did to you? Were the previous months all the same KWH value?

No. See the attached. (Left-click it to expand it to a more readable size.)

In the area I highlighted in yellow, the first column shows each 2-month billing period, the third colum is the number of KWH, and the fourth number is the bill. Don't panic -- it's in pesos, not dollars!

You'll note that if you do the math, the rate per KWH varies considerably, based on consumption. They determine the KWH rate by adding up the total KWH consumed in the previous 12 months (including the current billing period) and if it is more than 3,000 KWH for the year, your rate per KWH just about doubles. This is a fine idea in my opinion to encourage conservation.

tanstaafl.

edit: Oops -- I attached the wrong file -- no yellow highlights edited in. I'm talking about the grid near the bottom of the page.

db

I know this isn't exactly the same issue, but I'm on a water meter here in the UK.

When I first moved in I had stupidly low water bills, and the predicted meter readings on my bill were way off. Each time I would ring up with the correct reading and get told that it would work itself out and not to worry about it. About 4 years later they actually got around to sending a man in a van to read the actual meter. Of course there was a huge difference, this had a massive impact on my bill not only because of the missing water being billed for all in one go but the computer system assumed I got a pool or something and I'd be using that amount of water every quarter. I think my bill went up over night from something like £10 a month to £150.

After very much messing around I resolved the issue by coming off their stupid computerised pricing structure and just paying for the water I actually use. Maybe your electric company are in fact having some computer problems, one thing I have noticed when the companies in the UK have problems it's always in their favour

Cheers

Cris.

Hi,

Purchase a Kill-A-Watt P4400 from P3 International or off of ebay. They are around $30.00 US plus shipping.

It is a box that you plug into the wall and you plug your appliance (up to 1875 Watts) into it. It reads Voltage, Current, VA, Frequency, and Power Factor. It will give you a better idea of what each appliance is drawing. Be sure to check the Power Factor as they really might be charging for KVA instead of KWH.

It will also read KWH over time and show that as well.

Ross