2012年1月17日 星期二

Home Energy Saving Devices - Tools You Can Use to Find and Cut Waste in Your Home


In this article I'll cover two groups of home energy saving devices: first meters and monitors, which help you understand where your energy use is going; and second, indirect energy saving devices - devices made for another purpose that indirectly save you energy. I don't cover direct energy saving devices such as programmable thermostats, or gimmicks such as the device you connect to your power line that claims (unjustifiably, as far as I can tell) to cut your electricity costs by 20% or more.

Meters and monitors

If you really want to cut your energy use, understanding where the waste is will help a lot. In the meters and monitors category, there are four types of home energy saving devices worth mentioning.

Thermometers are one of the simplest devices for saving energy. Use them to measure the temperature of your refrigerator, freezer, or hot water, in order to adjust the temperature to a safe but energy efficient setting. You can also use them to find poorly insulated areas of your home. I discuss thermometers in more detail below.

Your utility meters are great measurement tools - get in the habit, at least for a couple of months, of reading the electricity meter every day (and the gas meter if you have one). Track your usage on a paper graph or in a spreadsheet and watch for changes. When daily readings spike, try to figure out the reason. Did you roast a turkey the day the electrical meter spiked? Or did someone accidentally leave the basement beer fridge door open? Did the gas usage go way up because of a cold spell, or because someone opened the spare bedroom window to air the room out, and then forgot to close it? Spikes in usage alert you that something needs to be checked. And when daily readings start to fall consistently week by week over a month or more, you know you've been doing something right in terms of cutting your energy use.

My family kept a graph of our electrical usage from the meter when we first started trying to cut our energy use, and we watched usage slide from over 10 kwh per day to as low as 6 kwh per day at one point. (That's about one fifth the average for homes in our area!)

Plug-in electricity monitors are the third home energy saving device in the meters and monitors category. Devices such as the Kill A Watt meter help you figure out how much electricity a given device or appliance uses. You plug the device into the meter, and the meter gives you readings for watts of power used as well as kilowatt hours over a period of time. You can use these meters to see how much energy you're losing to phantom loads such as AC to DC converters (which can draw a steady current even when nothing is attached to them) or anything with an LED or LCD display. You can also use these monitors to compare actual energy consumption of an appliance like a refrigerator, to what the manufacturer's claims say. For example, if your refrigerator is rated at 33 kwh per month and it uses 2.5 kwh in a one-day period, that's 75 kwh per month, so it may be time to adjust the refrigerator temperature, check the gasket for a good seal, or vacuum the coils at the back of the unit, then measure again.

The fourth category, full-house electricity monitors, track your electricity usage second by second so you can watch usage change as various devices are switched on and off. This is like the Cadillac version of reading your electricity meter yourself. But such monitors aren't always as useful as a plug-in monitor for figuring out how much a given appliance uses. Monitors such as The Energy Detective fall into this category. They are far more expensive than plug-in electricity monitors. For my money, the plug-in monitors are a better deal.

How to save energy with a thermometer

A digital thermometer with a remote probe can be used to save on refrigeration, hot water, and heating and cooling. If your refrigerator or freezer temperature is set too high, your food may spoil; if it is set too low, you are wasting electricity. To measure your refrigerator or freezer temperature, place the remote probe in a plastic jar half-filled with water; make sure the probe is submerged. Leave the jar in the refrigerator for at least one hour - at least 6 hours in the freezer. Then reset the thermometer's minimum and maximum temperatures, and wait a few more hours. Take the average of the new minimum and maximum readings and you know what the typical temperature of the appliance is. For a refrigerator, strive for 39F or 4C. For a chest freezer, you want 0F or -18C; for a refrigerator freezer, if you rotate the food within a few months, you can go as high as 5F or -15C.

Use your thermometer to measure hot water temperature, and lower the heater temperature if the hot water is above 120F or 49C. This not only reduces water heating costs, it means you're less likely to scald yourself.

To save on heating and cooling, use your remote probe to find outside wall areas that have poor insulation. On a particularly hot summer day or cold winter day, tape the probe to the drywall or plaster of exterior-facing walls, and take temperature readings in several areas in each room. (Wait a few minutes between measurements to allow the probe to balance to the temperature of the wall it is touching.) You may discover particular areas where the wall temperature is hotter in summer or colder in winter than other areas; these areas are probably poorly insulated or there are drafts behind them.

You can use the same technique to compare the thermal efficiency of different window panes. If the temperature inside one window pane is consistently lower than other window panes facing the same direction, you may want to consider replacing the window.

Indirect home energy saving devices

Some home energy saving devices were designed for another purpose, but indirectly they do save energy. Dimmer switches, which can be used for both lighting and fans, not only give you more control over lighting levels or fan speed, they reduce energy use when they are not on their maximum setting.

Automatic timers can save energy, but if they're used to turn lights or a radio on and off when you're out of the house (to fool the thieves) they actually increase your energy consumption, so at the very least make sure you use energy efficient light bulbs on any thief-distracting lights. Also make sure the purpose of the timed lighting isn't obvious from the outside - for example, my neighbor had a lamp with a bare bulb on an upstairs bedroom floor, and it was obvious from the outside that the light was just there to make the house look occupied. That's not going to stop a savvy thief!

Timers on bathroom fans are a great way to clear humidity or odors from the bathroom without the risk that someone forgets to turn the fan off and sucks all that heated or air-conditioned interior air to the out of doors. You can buy timer switches with a continuous dial, or with a range of preset times (30, 15, 10, 5 minutes for example).

Motion or infrared activated switches can also save energy. They sense movement or the body heat of a person entering the room, and turn the current on as you enter, then off again after the movement or heat is no longer detected. A screw-in motion detector lets you turn on a light from a switch, and then turns itself off after you've left, so even if you forget to turn it off, the light will shut down. Sensors are great for rooms you don't visit often, and where you're always forgetting to turn off the light.

Power bars can be great energy saving devices if you are disciplined about turning them off when the devices attached to them are no longer in use. Computers and accessories can continue drawing power even when you're not using them; a power bar with built-in surge protection not only protects your equipment from damage, but also cuts all power to the devices when you turn it off.

A small investment, a lot of savings

With a small investment in a few measurement tools - a thermometer, a Kill A Watt meter - and a bit of time learning to read your utility meter, you'll quickly identify many opportunities for cutting your energy use. Indirect energy saving devices will help you implement some of the opportunities you identify. Together, these two types of home energy saving devices can help you carve a big chunk out of your home energy bills.




Robin Green is the owner of GreenEnergyEfficientHomes.com, a website dedicated to helping people save energy on heating, cooling, lighting, and other energy uses in their homes. For more information see the Energy saving devices and Kill a watt meter pages on his website.





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