Electric meter techniques are strategies we deploy to extract electrical usage data from each and every device or appliance in the home. Starting with the simple power measurement of a 120 volt lamp, we move on and explore the various ways you can capture usage data for larger 240 volt appliances such as the air conditioner, clothes dryer or range using your electricity monitor.
To keep your electric meter data organized, we encourage you to use our home audit tool called the Power Panel Profiler. It is a comprehensive MS Excel spreadsheet that keeps track of every load in a 40-circuit, 200 amp panel and is FREE when you sign up for our bi-monthly newsletter called the Meter Messenger.
The simplest, lowest cost method of capturing power usage for 120 plug loads is to use a plug-in meter. To measure the power used by a lamp, for example, simply plug the lamp into the meter and plug the meter into the nearest outlet. Power will be shown in watts and, over time, energy will be displayed as kilowatt-hours. Most units allow a rate per kilowatt-hour to be entered so you can see the actual cost of electricity. This type of measurement is referred to as single point metering.
Net metering is a technique to use with a whole house electricity monitor or energy meter reader. It simply means to take the before and after power readings when a device is turned on or off and net out the difference. The benefit is that you do not have to install dedicated current transformers (CT's) to measure specific loads. However, isolating those specific loads can be challenging when various other loads are cycling on and off.
Load profiling is a method of tracking energy usage with software that recognizes the on/off signature of a particular load. When the device turns on, electric meter software recognizes the the size of the load and begins to log data. Likewise, when the device turns off, the specific decrease in load signals the software to stop logging. It works well for large loads that simply turn on and off like a hot water heater.
Sub-metering refers to measuring electric usage of an appliance, circuit, or sub-panel while the total electrical load of home is also being measured. This technique provides an accurate measurement of the power consumed by the appliance or sub-panel and represents it as percent of total load.
When all else fails, read the placard. Placards contain electrical consumption data and are found on most all appliances. These labels denote the voltage and current ratings for the device along with other electrical data. If your electric meter budget is rather limited, this is a way to make a reasonable estimate of the amount of power used. Apply a run time estimate to this power reading to obtain kilowatt-hours.
If you have a circuit level energy monitor, most of these techniques, excluding placard reading, will already be built into the software. If you do not have a circuit level monitor, consider putting these techniques to work to get the best possible information out of the electric meter system that you do have.