Issue #112
April 2011

Visit Home Energy

Table of Contents

eMonitor Update

What is a Btu Meter?

How Efficient is Your Lighting?

Ten Energy Saving Tips

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eMonitor Update
Powerhouse Dynamics introduced the eMonitor last year which is a circuit-level energy monitor. Home Energy ran an introductory article about the eMonitor in our June 2010 Meter Messenger E-zine. Since that time the folks at Powerhouse Dynamics have continued to improve their product.

Toward the end of 2010 they released a free iPhone app that is available through Apple iTunes. An Android app is planned for later this year. The app allows you to view how many watts your top circuits are using plus daily, weekly and monthly overall usage in kilowatt-watt hours and dollars over your phone. The eMonitor system updates every minute, and although the iPhone app runs a little slower, it is generally not a hindrance.

The eMonitor can interface with Google Power Meter for displaying overall usage by day, week or month over any web portal. Efficiency can be compared with similar sized homes. However, the interface is relatively basic and does not offer the circuit level data and analysis that the direct eMonitor web interface provides.

Another feature added to the web interface last year was the Phantom Power widget. It tracks those circuits that continue to draw power, even after the devices are turned off. Common culprits are computer peripherals, satellite receivers, DVR's and other home electronic appliances. Plugging these devices into timed or smart switching power strips can be a cost effective solution to eliminating these phantom or vampire loads.

More recently, Powerhouse Dynamics just released eMonitor 2.0. This new version of its web interface software strives to add "intelligence" to the eMonitor's capabilities by expanding analytics, diagnostics and alerts in a variety of ways. The Report Card, online or email, now provides personal savings recommendations which are derived from appliance trends and other key observations. Recommendations have financial impact quantified to help you prioritize their value.

The Alerts feature has been expanded to notify you of projected monthly energy costs before going over budget, a weekly comparison of usage and any peculiar circuit level activity that may reflect a refrigerator door being left open, for example. Selected alerts can be shared with friends and family on Facebook or Twitter. Additional sharing features provide you with your own personalized eMonitor Window where you can share selected information with friends or post on Facebook.

As a circuit-level monitor the cost of the eMonitor resides on the higher end of the home energy monitor spectrum and requires a web interface subscription to take advantage of all the features discussed. However, the information it provides can make the difference between saving 10 percent or 25 percent on your energy bill provided you act upon it.

What is a Btu Meter?

First off, let's define what a Btu is before we try to measure it. Btu stands for British Thermal Unit and refers to the amount of energy required to raise one pound of water one degree Fahrenheit. This unit of measure is used extensively to measure the performance of all heating and cooling systems. 12,000 Btu's equal one ton of air conditioning. The term "ton" is derived from the fact that it takes about 12,000 Btu to melt a ton of ice in a 24 hour period.

A Btu meter simply measures the amount of heat a device adds to a fluid over a specific interval of time. A Btu data logger, on the other hand, measures and records the amount of heat added over an extended period of time by recording data at fixed intervals such as 15 minutes.

From a home energy metering standpoint, a Btu meter is used to measure the efficiency of a solar thermal collector that provides household hot water or heats a swimming pool. To do this, we must capture the temperature of the cool water entering the collector, the temperature of the warm water leaving the collector and the rate at which the water flows through the collector.

BTU output of the solar collector increases as the difference between inlet and outlet temperatures increases, the flow rate increases or a combination of both. By taking measurements at different times of the day, under various weather conditions, a reasonable estimate of solar collector performance can be determined.

At Home Energy we offer an explanation of how to build a simple Btu meter for about $150. The components include a couple of digital temperature sensors and brass pipe nipples, available at most home centers, and a simple flow meter.

Inlet and outlet temperatures are taken while the flow rate is measured. Knowing the difference in temperature, or "delta T", and the flow rate in gallons per minute allows you to calculate the Btu output of the solar collector using the calculations found toward the bottom of our How to Build a Btu Meter page.

Once you know the Btu output per hour you can convert it to kilowatt-hours. Apply your electric bill rate per kilowatt-hour and you will know how much money your solar collector is saving on electricity.

How Efficient is Your Lighting?

What type of light bulbs do you use in your home? Incandescents, halogens, compact fluorescents (CFL's) or light emitting diodes (LED's)? From an efficiency standpoint, standard incandescents are the worst as they consume the greatest amount of energy per lumen of illumination. Halogens consume similar levels of energy but produce more light per watt. Incandescent and halogen bulbs are less expensive than CFL or LED bulbs.

CFL's offer a substantial decrease in energy consumption when compared with incandescents or halogens. For example, a 23 watt CFL can deliver the same amount of light that a 100 watt incandescent does. CFL's are more expensive than incandescents and halogens but prices have been dropping over the past couple of years. From an environmental standpoint though, CFL's have a drawback as they contain a slight amount of mercury.

LED bulbs are the most efficient and have extremely long life measured in tens of thousands of hours. However they are quite expensive costing five to ten times more than the other types. This high cost is driven in part by the fact that each LED uses a slight amount sapphire in its production. A newer technology using silicon, which is made from sand, should lower LED prices in the not too distant future.

Given these options, how can one sort out what is best for their home. At Home Energy we provide our Home Lighting Ideas page to help you answer these types of questions. Click on the Incandescent Lighting Comparison page to walk through a home office scenario.

This scenario compares the energy and replacement cost of four bulbs burning eight hours per day in a home office for a ten year period. Incandescent bulbs are the baseline. Energy consumption and replacement cost are compared with quartz halogens, CFL's and finally LED's. A ten year period is used because it brings the extremely long life of LED's into the fold.

Check it out and plug in the numbers for your home. You may find some real energy savings are lurking there.

Ten Energy Saving Tips

1. There are only three ways you can reduce your energy consumption:
a. Conserve by shutting things off, adjusting thermostats or installing dimmers.
b. Become more efficient by using devices that consume less energy to get the job done.
c. Install alternative energy generation sources such as solar PV, wind or micro-hydro.

2. Consider installing solar lighting along your sidewalk or beside pathways in your yard. Low voltage solar lights are easy to install, safe and require no energy from the grid to operate.

3. Open your swimming pool earlier this year and enjoy a longer season into early Fall by installing a solar pool heater. Circulation can be provided with an existing pool pump.

4. Choose ENERGY STAR labeled equipment for your home office. If you work from home eight hours per day, anything normally on during the day will run over 2000 hours per year. Every watt you save adds up to two kilowatt-hours at the end of the year.

5. Need to replace an air conditioner as the heating season rolls in? Look for a 13 to 16 SEER rated unit and buy the highest rating you can afford. Size it to meet the load but not exceed it. Larger compressors draw more power. Shorter cycle times translate into more humidity which requires more energy to remove it from the air.

6. Building a new home this year? Consider geothermal for heating and cooling if you are in a climate that does not have extreme winters (i.e. sub-zero temps for days at a time). SEER ratings can reach into the lower thirties which is much more efficient than any compressor driven cooling system.

7. Here's a quick rule of thumb for sizing a cooling system for a home. Plan to install one ton (12,000 Btu) of cooling for every 500 square feet of living space. Add 10% for sunny rooms and 50% for the area of the kitchen. Your HVAC contractor will make the final determination but this will get you in the ballpark.

8. Verify your refrigerator's temperature by placing a thermometer in a glass of water in the fridge for 24 hours. Place the thermometer between frozen packages in the freezer for a more accurate reading and check it after 24 hours. Refrigerators should read 37-40 degrees F. and freezers 0-5 degrees F.

9. Place a plug-in meter on your refrigerator or freezer. Check it after a week of normal family use. Compare this to a week when no one is home such as a family vacation. The difference is what it costs to open the door.

10. Whenever purchasing an appliance that uses high degree of energy (typically 220-240 volt) evaluate the life cycle cost to determine the best value. This should include ((Kilowatt-hours per Year x Energy Cost x Number of Years in Service) + Maintenance Cost + Purchase Price). The lowest number will be your best buy.

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