Replies

1. 
   BillHartmann | Jan 07, 2009 06:08pm | #1

   Not really.

   But you can make some guess. Which in some cases might be reaonsable, but way off in others.

   Voltage x current x POWER FACTOR gives the POWER USED in watts.

   You could use 1 for the power factor for heating load, .85 for motors, and .95 for other loads and get a reasonable results.

   But that is the POWER (or rate at which working being done) at that instant.

   But energy is the integral of the power over time. For something like a light bulb it is easy to see when it is on and the amount of power that is uses is constant.

   But something like a refrigerator would be impossible to figure. For example mine is an energy saver model. There is an internal fan and valve that will move cold air from the freezer to the refigerator section when needed. And I believe the evaporator and condensor fans run independently, as needed, and not just when the compressor is running. Then you have the defrost coils, ice maker, and light.

   The amount of power used at any one time is all over the map. And it is very hard to monitor the compressor and see how long it is running.

   .
   William the Geezer, the sequel to Billy the Kid - Shoe
2. 
   DanH | Jan 07, 2009 06:10pm | #2

   The best approach is to buy a clamp-on ammeter. They are available starting at about $75. You clamp plier-like jaws around a single wire in the breaker panel and measure the current in the wire.

   The mark of the immature man is that he wants to die nobly for a cause, while the mark of a mature man is that he wants to live humbly for one. --Wilhelm Stekel
3. 
   gfretwell | Jan 07, 2009 10:15pm | #3

   I am doing a little of this at my house as we speak. I figured out a side by side fridge pulls about .48a all the time and a tad over 2a when the compressor is running. The 1hp pool pump is 5.3a @240v. My pc, router, 12 port switch. DSL modem, display and all the other stuff is about 2a.

4. 
   Riversong | Jan 08, 2009 01:19am | #4

   Don't waste $75 on an ammeter, which will only show you what the appliance is using at the moment.

   For $25, you can get the Kill A Watt device you referred to, which monitors voltage, wattage, power factor, frequency, and total consumption over time.

   http://www.energyfederation.org/consumer/default.php/cPath/388_254

   http://www.p3international.com/brochures/P4400.pdf

    

   Riversong HouseWright

   Design *  * Build *  * Renovate *  * Consult
   Solar & Super-Insulated Healthy Homes
1. 
   DanH | Jan 08, 2009 01:28am | #5

   Of course, the Kill A Watt can't be used to measure a hard-wired circuit.
   The mark of the immature man is that he wants to die nobly for a cause, while the mark of a mature man is that he wants to live humbly for one. --Wilhelm Stekel

1. 
   Riversong | Jan 08, 2009 01:49am | #6

   No, it's only for 5-15P 120v corded appliances. 

   Riversong HouseWright

   Design *  * Build *  * Renovate *  * ConsultSolar & Super-Insulated Healthy Homes

2. 
   GaryGary | Jan 09, 2009 08:10pm | #7

   http://www.newegg.com has the Kill A Watts for $18 -- sometimes less.----
   As another option, the TED allows you to measure total house power use, or to measure power on any single circuit:
   http://www.theenergydetective.com/index.html
   They also sell software to log to your PC.I have had one for a couple months, and it works very well, but kind of pricey.Gary

1. 
   homedesign | Jan 09, 2009 08:51pm | #8

   There is always the low tech way

   kill a watt for the plug in stuff then...

   turn off all breakers and then switch on one at a time

   count the revolutions of the meter wheel over time

5. 
   arcflash | Jan 10, 2009 03:20am | #9

   You can check your electric bill and see how much energy all of the appliances use per month!

   An ammeter is a great buy for anyone wanting to troubleshoot electrical systems. Just be really careful in that panel. 200A would not feel good at all! Fluke and Ideal make the ammeters that I see the most often out in the field.

6. 
   Clewless1 | Jan 12, 2009 03:36pm | #10

   Use a clamp on amp meter ... make a pigtail out of a plug/outlet repair ends for extension cords ... use two separate wires or separate a length of corded/sheathed wire. It only has to be 6-12" long. Plug your device into it and plug it into the wall. Take an amp reading and do the math ... badda boom ... you have energy draw. Now multiply by hours of use over a period of time and you have KWH.

1. 
   DanH | Jan 12, 2009 03:52pm | #11

   Most clamp-on meters come with a plug-in adapter.
   God is REAL, unless explicitly declared INTEGER

1. 
   Clewless1 | Jan 12, 2009 05:12pm | #12

   I've bought a few and never seen that.

1. 
   DanH | Jan 12, 2009 05:50pm | #13

   The one I've got has two holes for the meter clamp, one 1x and one 10x.
   God is REAL, unless explicitly declared INTEGER