If you want to record your electricity use, display it in real-time on a computer, analyse each household appliance and loads, project your daily-weekly-monthly cost of energy, detect the onset of a peak demand situation, locate inefficient loads and reduce your electric bill, then you're at the right place.

Here's a brief overview of the different types of Energy/Electricity Monitors typically available, pointing out their strengths and weaknesses.

This overview is broken down into the following:

• Method of measuring Power (electricity)

• Transmission of the Data to the Display Unit.

• Capability of Recording Information to view on a Computer.

• Interface to a Computer

• Capability of detecting excess usage

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Method of Measuring Power (electricity):

As far as we a aware, there are four types of methods of obtaining the consumption of energy/electricity, commonly used by various manufacturers. The reason for the "/electricity" in the previous sentence is that for one of the described method, energy (power) is not what is metered. The measurement is that of current only, which can only make assumptions of KWh and possibly create extreme errors.

The four common methods of metering, as displayed below, are:

1.	Measurement of voltage and current at the service panel using sensors or transformers. These two values are processed to generate a "true power" which in turn is compiled in to kilowatt-hour as energy is consumed.
2.	Measurement of current only from the service panel using sensors or transformers.
3.	An electronic eye is placed on the "House Meter" to count the rotations of the meter's rotating wheel.
4.	Installation of a "smart meter" by the power company. This meter has the ability of tracking power usage and the time of use.

 

1. Two sensors are place on the two incoming "Line" wires feeding the panel. The voltage is monitored by connecting wires directly to a panel circuit or by plugging a step-down transformer into a nearby outlet.   PROS: Accurate Power value may be generated when using quality sensors and support electronics. CONS: Requires more expensive sensors with low "phase shift". More electronics and firmware required to calculate "True Power"	Larger View
2. Two sensors are place on the two incoming "Line" wires feeding the panel. PROS: Low Cost sensors and minimal electronics allow this product to be manufactured at a low cost. CONS: Falsely assumes KWh value The Voltage, the Power Factor and the voltage Wave Shape are all assumed values. Extremely poor KWh accuracy. Should not be used for appliance replacement program due to false readings. If the actual line voltage sways lower than the assumed, ever greater error is generated. For certain types of loads, "energy" reading errors of 100% (double the real amount) is possible. (see chart) Sometimes operates on batteries, which requires periodic replacement. Usually will make it seem as though you are using more energy than you actually are. (based on the principle of assuming unity PF and 120VAC)	Larger View
3. A photo-eye sensor is installed on the face of electro-mechanical meters. PROS: Much lower cost than using current sensors. Safe installations, may be performed by consumer. CONS: Improper alignment can cause errors undetectable by consumer. May be affected by climate. Requires batteries (for the wireless models) which may be a nuisance to replace during bad weather conditions. At low power levels typical of those when you leave home, it may take several minutes to update the display to indicate the power usage. Poor resolution and refresh time. Cannot display voltage or current. Unable to display energy for each individual panel phase.	Larger View
4. The electro-mechanical meter is replaced with a digital type with wireless communication capability for AMR (automatic meter reading) by the power company. PROS: Capable of highest accuracy More detailed billing information. CONS: Meter and communications infrastructure expensive to implement and maintain. Although provided by the Utility company, the consumer ultimately pays the cost. Consumer has no control or direct real-time data. Not conducive to analysis of home energy situations. Lack of available signal for load-shedding purposes. (This information is based on findings of typical "smart meter" researched from the internet. This does not signify that all makes or models of "smart meters" are incapable of the  functions described in the "CONS" column)	SMART METER

Transmission of the Data to the Display Unit:  ...  under construction

Do it Right!

If you're about to take up some of your valuable time to assess and reduce your Energy Use, get the right tool for the job!

When deciding on a Home Electricity Monitor, ask yourself the following:

• Is it reporting accurate data (KWh or $) based on "true power"? Don't be afraid to ask the company your buying from.
• Can it detect/record loads coming on when you're not home or sleeping? If so, can it tell you how much power it used and how long it was on for?
• If its only means of communication is RF wireless, what happens when communication becomes intermittent due to range or interference? Is it on a mesh network to overcome these issues by using router(s)?
• If its only means of communication is powerline carrier (data modulated on the electrical wiring), what happens when communication becomes intermittent due to loads shunting the signal or connection to opposite phase? Is there an alternate means of communication?
• Can you interface it with a PC? Is the monitor capable of sending "real time" data or recorded data?
• How often is the displayed power updated?
• Do you really need features like CO2 emissions, temperature, power factor?

Dear Potential Customer,

I recently had to purchase a piece of equipment in a field I didn't know much about. After browsing the internet, I noticed that there were many types, covering a wide price range. I was getting more and more confused until I came upon one vendor's site. This company presented a summary of the various types and makes, indicating their strengths and weaknesses. It also presented which features were important and not so important based on the customers' requirements.

This companies' web site saved me a lot of heartache and money. Prior to discovering this chart, a comparison of price and features from browsing the internet put my eyes on one particular machine. Ultimately, this machine would have performed poorly due to shortfalls pointed out in the summary.

As it turns out, the company presenting the summary clearly had the best machine and that is the one I bought. Although slightly more expensive, I would have lost the difference in cost in no time due to poor machine performance and capabilities from other models.

I was very grateful for the summary which was presented by this company. I then made the decision to provide our potential customers with a similar comparison.

P. Brule

President

  ©Brultech Research Inc 

 

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