Electricity Usage Monitor

This is the place for any magazine-related discussions that don't fit in any of the column discussion boards below.
Post Reply
Bigglez
Posts: 1282
Joined: Mon Oct 15, 2007 7:39 pm
Contact:

Electricity Usage Monitor

Post by Bigglez »

I'm curious to know how utility electricity is consumed in
our home. I found these products on Amazon:
P3 International P4400 Kill A Watt Electricity Usage Monitor
P3 International P4460 Kill A Watt EZ Electricity Usage Monitor

Has anyone used one of these? Or, is there another tool
available to do the same task?
User avatar
haklesup
Posts: 3136
Joined: Thu Aug 01, 2002 1:01 am
Location: San Jose CA
Contact:

Re: Electricity Usage Monitor

Post by haklesup »

I've used the P4400, not sure what the difference is to the p4460 except the obvious new case.

It's useful for one appliance at a time. It will tell you what that applicance consumes depending on how long you leave it connected but beyond that, the calcualtions are all manual. For example if you want to know how efficient a new refridgerator will be, you really need to buy it and run it for a few weeks and compare that to your old fridge before you unplugged it for good. It's useful to compare like appliances you own (like which TV is more power hungry) and to learn exactly how much power is wasted by standby modes and wall warts etc but its learned one thing at a time. BTW, it resets to 0 when unplugged. Over time, you can build up a decent profile of your usage.

If your power company has a smart power meter which you can see stats online then you should ask to get one of those as it will give you a bigger picture. Unfortunately, these are available in only limited areas but it's growing fast.
User avatar
dacflyer
Posts: 4748
Joined: Fri Feb 08, 2002 1:01 am
Location: USA / North Carolina / Fayetteville
Contact:

Re: Electricity Usage Monitor

Post by dacflyer »

i have the 4400 also..but it holds no memory. the 4460 does. plus it has a few other features.
but the 4400 has a minor flaw, the display only shows 59.9Hz..even tho it does monitor 60HZ
the 4460 has this flaw corrected. all in all they are both good meters, but the 4400 is hard to read, depending on where it is plugged in.. the 4460 can be removed, and relocated to a easier place to read the info,, not sure if it can be read while it is unplugged.. i think it has battery back up for memory.
Bigglez
Posts: 1282
Joined: Mon Oct 15, 2007 7:39 pm
Contact:

Re: Electricity Usage Monitor

Post by Bigglez »

haklesup wrote: I've used the P4400, not sure what the difference is to the p4460 except the obvious new case.
Thanks for the quick reply. I guess I'll know more after
buying and using one for a while.
haklesup wrote:BTW, it resets to 0 when unplugged.
manual for the P4460 wrote:1. When power to the Kill A Watt™ EZ is interrupted, the display will go blank and the unit will stop measuring consumption and elapsed time. However all accumulated measurements including KWH, Elapsed Time, and actual total cost will be retained.
haklesup wrote: If your power company has a smart power meter which you can see stats online then you should ask to get one of those as it will give you a bigger picture. Unfortunately, these are available in only limited areas but it's growing fast.
I borrowed one from the local PG&E office some years ago.
It was a regular Kw-hr meter with 120V one phase wiring
and an outlet.

Perhaps my biggest electrical energy hogs are the 240V
motors on the pool pumps (two of them).

I strongly suspect our home entertainment costs are much
higher than in years gone by. The 46inch HDTV is rated at
285Watts, and we use the AVR and Sub-woofer, too. So I'd
estimate 500W for this function within our home.

Neither of the two refrigerators are less than about eight
years old, and the zoned gas-fired HVAC probably has
an 800W blower motor. (Not to mention the three tons of
AC that we run in the summer...)

The local rates are high by national standards, and higher
consumption begets higher rates - the opposite of "volume
discount"!

Stay tuned!
User avatar
Bob Scott
Posts: 1192
Joined: Wed Nov 20, 2002 1:01 am
Location: Vancouver, BC
Contact:

Re: Electricity Usage Monitor

Post by Bob Scott »

Bigglez wrote:Neither of the two refrigerators are less than about eight years old, and the zoned gas-fired HVAC probably has an 800W blower motor. (Not to mention the three tons of
AC that we run in the summer...)
The fridges? They're like using electric heat in the wintertime. After you've calculated the electric power consumption of the refrigerators, you should calculate how much money you are saving in gas by using the fridges to help heat the house. Of course, if you use AC in the summertime, you'll have to pay extra on the AC bill to get rid of that fridge heat.

My furnace uses a standard big squirrel cage motor driven by a 1/4 HP motor. That's only ~190W whan fully loaded. However, it sucks 5 amps of inductive current when unloaded. It's a good thing the residential power meters are smart enough to ignore reactive current. I added a 36,000 BTU central air AC to the furnace in my previous house and had to bump up the motor to 1/2 HP (with a larger pulley) or the evaporator coils would freeze. I think your estimate of 800W for your blower motor is a bit high.
Bigglez wrote:The local rates are high by national standards, and higher
consumption begets higher rates - the opposite of "volume discount"
We have a volume penalty too. Any extra power is billed at C$ 0.07/KWH (~US$ 0.056/KWH). Our gas is cheaper in energy content than electricity, ~US$ 9.33/million BTU.

What are your rates like?
-=VA7KOR=- My solar system includes Pluto.
Bigglez
Posts: 1282
Joined: Mon Oct 15, 2007 7:39 pm
Contact:

Re: Electricity Usage Monitor

Post by Bigglez »

Bob Scott wrote:
Bigglez wrote:The local rates are high by national standards, and higher
consumption begets higher rates - the opposite of "volume discount"
We have a volume penalty too. Any extra power is billed at C$ 0.07/KWH (~US$ 0.056/KWH). Our gas is cheaper in energy content than electricity, ~US$ 9.33/million BTU.
What are your rates like?
Tier 1 (Baseline)
$0.11531
Tier 2 (101-130% of baseline)
$0.13109
Tier 3 (131-200% of baseline)
$0.25974
Tier 4 (201-300% of baseline)
$0.37866
Tier 4 (201-300% of baseline)
$0.37866
Tier 5 (Over 300% of baseline)
$0.44098
Tier 5 (Over 300% of baseline)
$0.44098
"Average" (per kWh)
$0.17643

The baseline tariff varies by a complex formula, for
practical purposes assume it's 30 - 40 Kw-hr per
day in the winter. So, 900 - 1200 kW-hr per month.

Okay, given the time crunch before my work day, that's
the raw data from PGE.com for residential metered
electricity, effective March 2009. Should be self-explanatory.
User avatar
haklesup
Posts: 3136
Joined: Thu Aug 01, 2002 1:01 am
Location: San Jose CA
Contact:

Re: Electricity Usage Monitor

Post by haklesup »

The fridges? They're like using electric heat in the wintertime. After you've calculated the electric power consumption of the refrigerators, you should calculate how much money you are saving in gas by using the fridges to help heat the house. Of course, if you use AC in the summertime, you'll have to pay extra on the AC bill to get rid of that fridge heat.
That's a really interesting point you bring up. It should be possible to build some sort of ventilation behind the fridge to either remove the heat outside or inside (depending on the season). While I don't have A/C (for the 7-14 days a year when its needed) it might make a difference in comfort and maybe even improve the efficiency of the fridge at times. I think it would need to be passive ventilation. I suspect the benefit would be small enough to be negated by a fan.

Bigglez, for the larger 240V loads, your simpler method would be to use a current clamp and a DMM with datalogging capability. Kill-A watt does have 240V versions you should be able to find it on eBay from a European seller.

Sounds like what you borrowed from PG&E wasn't a smart meter but an early mechanical version of the P4400.

I've occasionally considered a video based approach to watching a standard watt meter. Maybe a web cam and machine vision software to read the dials and clock the spinning wheel. Hardware is simple but software could be a challenge. Anyone know of a software package that can do this?
bodgy
Posts: 1044
Joined: Tue Dec 04, 2001 1:01 am
Location: Australia
Contact:

Re: Electricity Usage Monitor

Post by bodgy »

I am saddened Bigglez that you are not considering building either of the consumption meters in the app notes on the Microchip or Texas Instruments website or the note from the Allegro power interface chip! :mrgreen:

There was a simple meter project in EPE magazine back around 1999 which I built - worked fine until a spider versus electron situation occurred and wiped out a transformer - used an expensive LEM hall effect module for current sensing.

Colin
On a clear disk you can seek forever.
Bigglez
Posts: 1282
Joined: Mon Oct 15, 2007 7:39 pm
Contact:

Re: Electricity Usage Monitor

Post by Bigglez »

bodgy wrote:I am saddened Bigglez that you are not considering building either of the consumption meters in the app notes on the Microchip or Texas Instruments website or the note from the Allegro power interface chip!
Actually, I've been over those app notes several times,
and considered rolling my own energy logger. I think it
would be a fun project! However, I'm just getting around
to building other stuff I thought of five years ago...

So for this project I plan to buy two of the 120V meters,
satisfy myself that they really work, and deploy them
in our home for various data logging tasks.

A 240V two-phase meter would be needed for the pool pumps,
AC compressor, and any other large loads, so that will have
to wait.

One tricky area is incandescent lighting. Or any wired-in
branch circuitry that we use frequently and don't know the
energy cost structure.
Post Reply

Who is online

Users browsing this forum: No registered users and 41 guests