While you’re probably already in the habit of tracking household
energy costs, prices change over time. A more meaningful and precise
indicator of energy use is consumption: how many units of energy you
use over a given period of time. You want to understand your usage in terms of kilowatt-hours,
therms, cubic feet, gallons, pounds, or cords; you want to know how much
of each fuel you use and when. With this knowledge you can begin to see why you use
what you do and then make a plan of action to save.
The specifics of how you monitor your home’s energy use depends on the fuel
you want to measure, how much detail you want, how you will use the information
you gather, and your budget. The information you get from monitoring your energy
use can be invaluable in discovering energy wasters in your home and identifying
savings solutions.
This chapter introduces you to some of the popular products and approaches to
real-time energy monitoring and data logging. Keep in mind that this is a dynamic,
emerging market, and there are many additional options out there, as well as smartgrid
products and applications used by electric utility companies.
Electric Energy Monitoring
Through the help of technology (and perhaps your electric company, if the “smart grid” has come to your neighborhood), you can monitor energy use by the minute, day, week, month, or year. You can look at whole-house information or just the use of a single appliance. By far the most advanced and user-friendly home-based energy monitoring technology has been applied to electrical usage. There are easy-to-use products for monitoring electricity at the appliance (point of use or plugload) level and at the whole-house level.
Point-of-Use Monitoring
plug-in electric meters, such as the Kill A Watt and Watts Up?, have become affordable and widely available. With these devices you can record how much power (in watts) an individual appliance is using in real time, as well as how much energy (in kilowatt-hours) it uses over a period of time. There are even some power strips available that let you monitor the electric use of everything plugged into them, such as your home office equipment or entertainment center. With this information you can discover the most efficient operating modes of various plug-in appliances and electronic equipment as well as determine whether or not a more efficient appliance would be cost-effective.
These meters accumulate the data and report the electrical consumption over time in kilowatthours so that (with a little programming of the meter) you can see how much that appliance is costing you. The power draw of some appliances varies depending upon what that appliance is doing. For example, a refrigerator has a compressor and fans that cycle on and off, and periodically enters into defrost mode. Each of these modes has a different power requirement.
If you want to know the energy consumption of a refrigerator, or anything else that cycles on and off, a plug-in meter that measures kilowatt-hours offers the most accurate reading. You can sort out nearly all the electrical use in your house with great specificity by moving a point-of-use meter from one appliance to the next, making notes, and adding things up. However, one limitation of plug-in meters is that they are limited to 120-volt appliances; they won’t work with 240-volt appliances, such as electric clothes dryers or water heaters.
Gas Monitoring
Monitoring n atur a l or propane gas use is somewhat less user-friendly than electrical monitoring. This is primarily because metering gas usage for each appliance involves cutting the gas supply line for that appliance and installing a dedicated meter with a dial or pulse output. For example, Itron (see Resources) manufactures various sizes of gas meters with integrated pulse output modules.
Every turn of the meter dial produces an electrical pulse that can be captured, counted, and electronically manipulated, and the results can be displayed graphically on a dashboard or on a spreadsheet. There are ultrasonic meter products that simply clamp onto gas supply lines, but currently these are quite costly. For accurate metering of a specific gas appliance in your home, you can use a pulse-enabled gas meter in conjunction with a pulse data collection logger. Many different kinds of sensors and data loggers are available from data logging product manufacturers, such as Onset, Omega Engineering, and Campbell Scientific (see Resources).
Reading Your Gas and Electric Meters
Electric and natural gas utilities provide you with a service meter that you can learn to use for monitoring the various appliances in your home. Contact your utility if you need help deciphering dials and numbers, and the quantity of energy each spin of the dial represents. Using gas as an example, the concept is simple:
Inventory all the gas appliances in your home, and understand what makes them turn on and off. Then turn off all of the appliances. Read the gas meter’s dials to get a starting point, then turn on the one gas appliance you wish to monitor. For example, if you want to know how much gas your clothes dryer uses, make sure that the heat (furnace, boiler, etc.) and hot water heater are turned off, and don’t cook during the test. Don’t worry about the pilot lights still being on; they use a negligible amount of gas. Now, operate the clothes dryer, and when it’s finished, read the gas meter again.
Subtract the initial reading from the final, and the result is the gas consumption of drying a load of clothes. If the meter reads in cubic feet, and the dryer used 30 cubic feet, you’ve used 30,000 Btus of gas (there are approximately 1,000 Btus in a cubic foot of natural gas). Multiply this by the number of dryer loads you do each month, and that’s your total Btu energy consumption for that appliance. Unfortunately, many gas meters read in increments of 100 cubic feet, so you might need to lengthen the duration of the test.
Finally, you need to know how your gas company bills you. It charges for gas by volume (in cubic feet, hundreds of cubic feet, or thousands of cubic feet) or energy content (therms or Btus). Once you know how many Btus are in one billable unit of gas, a little more math will show how much each dryer load costs. You can follow this routine for any gas appliance in your home, or use the disaggregation methodology described in chapter 2. This same approach works equally well with electric meters.
Bottled Gas
If you use bottled gas, typically there is no meter involved. Your only clue may be the percentfull gauge on the tank, and that’s not accurate enough for the metering method described above. If you’re determined to monitor bottled gas consumption, you can have a whole-house gas meter installed for a few hundred dollars.
Electric Energy Monitoring
Through the help of technology (and perhaps your electric company, if the “smart grid” has come to your neighborhood), you can monitor energy use by the minute, day, week, month, or year. You can look at whole-house information or just the use of a single appliance. By far the most advanced and user-friendly home-based energy monitoring technology has been applied to electrical usage. There are easy-to-use products for monitoring electricity at the appliance (point of use or plugload) level and at the whole-house level.
Point-of-Use Monitoring
plug-in electric meters, such as the Kill A Watt and Watts Up?, have become affordable and widely available. With these devices you can record how much power (in watts) an individual appliance is using in real time, as well as how much energy (in kilowatt-hours) it uses over a period of time. There are even some power strips available that let you monitor the electric use of everything plugged into them, such as your home office equipment or entertainment center. With this information you can discover the most efficient operating modes of various plug-in appliances and electronic equipment as well as determine whether or not a more efficient appliance would be cost-effective.
These meters accumulate the data and report the electrical consumption over time in kilowatthours so that (with a little programming of the meter) you can see how much that appliance is costing you. The power draw of some appliances varies depending upon what that appliance is doing. For example, a refrigerator has a compressor and fans that cycle on and off, and periodically enters into defrost mode. Each of these modes has a different power requirement.
If you want to know the energy consumption of a refrigerator, or anything else that cycles on and off, a plug-in meter that measures kilowatt-hours offers the most accurate reading. You can sort out nearly all the electrical use in your house with great specificity by moving a point-of-use meter from one appliance to the next, making notes, and adding things up. However, one limitation of plug-in meters is that they are limited to 120-volt appliances; they won’t work with 240-volt appliances, such as electric clothes dryers or water heaters.
Gas Monitoring
Monitoring n atur a l or propane gas use is somewhat less user-friendly than electrical monitoring. This is primarily because metering gas usage for each appliance involves cutting the gas supply line for that appliance and installing a dedicated meter with a dial or pulse output. For example, Itron (see Resources) manufactures various sizes of gas meters with integrated pulse output modules.
Every turn of the meter dial produces an electrical pulse that can be captured, counted, and electronically manipulated, and the results can be displayed graphically on a dashboard or on a spreadsheet. There are ultrasonic meter products that simply clamp onto gas supply lines, but currently these are quite costly. For accurate metering of a specific gas appliance in your home, you can use a pulse-enabled gas meter in conjunction with a pulse data collection logger. Many different kinds of sensors and data loggers are available from data logging product manufacturers, such as Onset, Omega Engineering, and Campbell Scientific (see Resources).
Reading Your Gas and Electric Meters
Electric and natural gas utilities provide you with a service meter that you can learn to use for monitoring the various appliances in your home. Contact your utility if you need help deciphering dials and numbers, and the quantity of energy each spin of the dial represents. Using gas as an example, the concept is simple:
Inventory all the gas appliances in your home, and understand what makes them turn on and off. Then turn off all of the appliances. Read the gas meter’s dials to get a starting point, then turn on the one gas appliance you wish to monitor. For example, if you want to know how much gas your clothes dryer uses, make sure that the heat (furnace, boiler, etc.) and hot water heater are turned off, and don’t cook during the test. Don’t worry about the pilot lights still being on; they use a negligible amount of gas. Now, operate the clothes dryer, and when it’s finished, read the gas meter again.
Subtract the initial reading from the final, and the result is the gas consumption of drying a load of clothes. If the meter reads in cubic feet, and the dryer used 30 cubic feet, you’ve used 30,000 Btus of gas (there are approximately 1,000 Btus in a cubic foot of natural gas). Multiply this by the number of dryer loads you do each month, and that’s your total Btu energy consumption for that appliance. Unfortunately, many gas meters read in increments of 100 cubic feet, so you might need to lengthen the duration of the test.
Finally, you need to know how your gas company bills you. It charges for gas by volume (in cubic feet, hundreds of cubic feet, or thousands of cubic feet) or energy content (therms or Btus). Once you know how many Btus are in one billable unit of gas, a little more math will show how much each dryer load costs. You can follow this routine for any gas appliance in your home, or use the disaggregation methodology described in chapter 2. This same approach works equally well with electric meters.
Bottled Gas
If you use bottled gas, typically there is no meter involved. Your only clue may be the percentfull gauge on the tank, and that’s not accurate enough for the metering method described above. If you’re determined to monitor bottled gas consumption, you can have a whole-house gas meter installed for a few hundred dollars.
