Issue #105, September 2010
Visit Home Energy

Table of Contents

eGauge Energy Monitor

Sleeping for Kilowatt Hours

What is Sub-metering?

Ten Energy Saving Tips

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eGauge Energy Monitor
The eGauge energy monitor system we have featured on our multi-point monitor page is now available on our eGauge page. The eGauge system offers up to twelve channels of monitoring capability per unit and can even work with three phase power systems. Recent firmware upgrades allow it to interface with BACnet building automation systems and Google PowerMeter. These capabilities allow the eGauge to not only serve the residential market but small commercial, as well.

One of the most striking features of the eGauge monitor is its ability to track grid power consumption and alternative energy generation simultaneously. Its dashboard defaults to a 48 hour rolling window of of energy generation and consumption history along side a dynamic power meter. Time frame flexibility allows the window to adjust from a minimum of one hour to a maximum of 30 years.

The eGauge website hosts output from a myriad of units operating in the field. Click here to view examples of actual eGauge monitors at work. When a unit is installed it automatically shows up on the device list at This is helpful during installation and provides access to your egauge monitor from anywhere on the Web. One can always opt out if they do not want to use the service.

The unit comes standard with three current transformers (CT's). Two 100 amp CT's are used for tracking power incoming to a standard 200 amp panel. The third CT is used to sub-meter an appliance or capture alternative power generation from a solar panel or wind turbine. Up to 9 CT's of various sizes can be added to track appliances or generation sources. Special pricing is offered when additional CT's are ordered with the eGauge monitor kit.

Since the system is designed to accept up to 277 volts per channel, incoming three phase power can be monitored using three channels. The remaining nine channels can sub-meter three additional 3-phase loads or any combination of 3-phase, 2-phase (240 volt) or single phase (120 volt) loads. If additional monitoring is required, future enhancements will allow main modules to be linked together offering twelve additional channels per module.

Internal memory of the eGauge monitor can store over a million records. This translates to recording up to one year of history on a one-minute interval plus an additional 29 years of history using half hour intervals which is useful for tracking solar panel degradation over long periods of time.

The eGauge does not have a display unit of its own but uses power line transfer technology to send data over existing wiring to a home plug module. The module is simply plugged into any outlet near an Ethernet router or switch where it is connected with a Cat 5 cable. This allows you to monitor energy and power directly from any PC browser on your local network. Once registered on the eGauge website, your power generation and usage can be accessed from anywhere on the Net including smart phones, iPads and Andriod tablets.

The system is priced at $495 with a 3-month warranty or $652 with a 5-year warranty that includes full technical support. There are no subscription fees to maintain a presence on the eGauge web site nor are there any costs for future firmware upgrades.

This is a robust unit that lends itself well to larger homes and/or small commercial applications - especially with it's 3-phase capability. Even smaller homes using solar or wind power will find the eGauge very useful in tracking alternative power generation.

Sleeping for Kilowatt-hours
Which category uses the most energy?

A. Large data centers
B. Business computers
C. Home computers and electronics

If you guessed A or B, you loose a point. According to a recent study done by Lawrence Berkeley National Laboratory (LBL) researchers, home computers and their peripherals consume more energy than business computers and large data centers combined when the cooling costs for these large systems are excluded. Numbers from the study show data centers to use 37.9 terra-watts (as in trillion), business computers 89.8 terra-watts and home computers and electronics a huge 161.9 terra-watts.

The reason is that so many home computers are left on all the time. It's OK to shut them off, however, many do folks not want to miss updates, interrupt network access or be unable to stream music at a moments notice. So, the machines just remain on, in idle mode, all the time.

New technologies are emerging that will reduce idle mode energy consumption by 95% by entering the device into "sleep" mode. Updates, network access and music streaming will activate when summoned to do so but power consumption during idle time will be cut dramatically. Think of it as a replacement for the off-state on many devices without having to deal with the inconvenience of disconnection.

Three approaches to developing the new "sleep state" include energy efficient Ethernet, network proxying and streamlining streaming. A new standard called IEEE 802.3az outlines how Ethernet power consumption can be cut by 50% while increasing bandwidth. It calls for a low power idle or "sleep mode" on network devices when they are not actively transmitting data. Power levels on these devices during sleep mode can be dropped by 90% according to LBL researchers resulting in an annual energy savings of $450 million in the U.S. alone.

Network proxying allows computers to continue to share data while in sleep mode and holds even greater promise of energy savings then IEEE 802.3az. The technology is built directly into SmartNIC's (Network Interface Cards). Apple Computer's Snow Leopard operating system makes use of this by searching for iTunes audio files on networked computers even if they are asleep. A standard is in the final stages of approval and will be adopted in devices such as printers, set-top boxes and video game consoles soon.

Streamlining streaming refers to the ability of one electronic device to know the on-off state of a device it is connected to. For example, DVD player does not know if the television to which it is connected is on or off. If the DVD player remains on when the television is turned off, or receives its signal form another source, the DVD could display its menu for weeks. Moving from the two-state "on-off" world to the three state "on-off-sleep" world will save a significant number of kilowatt-hours when devices can communicate intelligently with each other through a home energy management system.

Standards development for this inter-device communication is vigorously underway as part of the Smart Grid Initiative but that's an article for another day...

What Is Sub-metering?
The term sub-metering is used frequently throughout the Home Energy website. The hardware and wiring associated with sub-metering are explored in depth on our Sub-metering page. The purpose of this article is provide some pointers for good sub-metering practices that will result in saving energy and money.

The whole idea behind sub-metering is to measure larger loads individually, in addition to the total load, to gain a better understanding of how power is used in your home. Large loads typically include the 240 volt circuits for the HVAC system, hot water heater, clothes dryer and range. A small improvement in the run time of a four kilowatt heat pump or an eight kilowatt heat strip will save much more energy than turning off that 75 watt table lamp a little sooner.

Sub-metering provides an energy usage baseline for a specific device over an extended period of time. Using this baseline, one can measure how energy consumption changes over time when improvements are made to the system. For example, installing a programmable thermostat may prove to be a great energy saving device during the warmer months. However, if temperature setbacks of three degrees or more are used during the colder months, supplemental heat strips may kick on more frequently negating any energy savings from the lower thermostat settings. Sub-meter measurement will verify this, one way or the other.

When selecting a home energy meter, consider the number of appliances or devices you would like to sub-meter. The number of channels on the energy monitor reflect the number of current transformers (CT's) that can be installed. Remember that the larger 240 volt loads will require two CT's for each circuit. Smaller 120 volt loads will only need a single CT.

When it comes to sub-metering 120 volt loads, consider placing CT's on just those circuits that are hard-wired, such as the dishwasher, microwave or recessed lighting arrays. If you have a limited number of channels available, consider moving the CT's to another breaker once a baseline has been established. If the device has a standard plug, it's energy consumption can be measured with an inexpensive plug-in meter. Use our Power Panel Profiler to compile data from multiple sources as you build your home energy baseline.

Sub-metering, like most anything, has its trade offs. The cost of additional CT's must be weighed against potential energy savings. Sub-metering a low use bedroom circuit will generally not be cost effective. However, if you have a teenager that can't find the off switch when they leave their room, it might be another matter.

For more information about the sub-metering capacity of various home energy monitors, look for the number of channels available in our multi-point monitor product comparison table.

Ten Energy Saving Tips
As cooler weather in just around the corner keep these tips in mind...

1. Check weather stripping around and underneath doors. Replace if torn or damaged.

2. Caulk around windows that leak air but leave a small gap at the base of the window for any condensed moisture to escape.

3. Use expanding foam around the outside of outlet boxes and place foam gaskets behind outlet and switch plates.

4. Look for dirty spots on painted walls and ceilings which may indicate air leaks exist through the wallboard. Caulk to seal and repaint to touch up.

5. Replace single pane windows with double glazed ones or install storm windows before temperatures drop too much.

6. Consider using a kitchen exhaust fan cover to keep warm air from escaping when the fan is not in use. Covers attach with magnets and are easy to remove.

7. Be sure to close your fireplace damper as soon as you are sure the fire has gone out. Chimneys not only expel smoke but warm air as well - 24/7 if the damper is left open.

8. If your home uses radiators, place heat-resistant reflectors between the radiator and exterior wall.

9. Check warm air registers and/or baseboard heaters to be sure they are not blocked by furniture, carpet or drapes.

10. Check air ducts for gaps, tears or leaks and repair them. Heat entering your attic or crawl space will add no benefit to your personal or financial comfort during the winter months.

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