Appliances - How Much Electricity Do Home Appliances Use? - 4/1/2004 - Home Interior Kitchen Appliances

Appliances - How Much Electricity Do Home Appliances Use?

If you want a general estimate of how much electricity your home appliances consume, you can refer to Figure 9, which provides the energy consumption (Wattage) of some typical home appliances. If you have appliances that are not listed in the table, or desire a more exact figure based on a specific appliance in your home, use the following formula to estimate the amount of energy a specific appliance consumes: 

Wattage x Hours Used Per Day
1000

= Daily Kilowatt-hour (kWh) consumption
(1 kilowatt (kW) = 1,000 Watts)

Multiply this by the number of days you use the appliance during the year for the annual consumption. You can then calculate the annual cost to run an appliance by multiplying the kWh per year by your local utility's rate per kWh consumed. Here are some examples:

* Window fan:

200 Watts x 4 hours/day x 120 days/year
1000

= 96 kWh x 8.5 Cents/kWh
= $8.16 /year

* Personal Computer and Monitor:

(120+150) Watts x 4 hours/day x 365 days/year
1000

= 394 kWh x 8.5 Cents/kWh
= $33.51/year

You can usually find the wattage of most appliances stamped on the bottom or back of the appliance, or on its "nameplate." The wattage listed is the maximum power drawn by the appliance. Since many appliances have a range of settings (for example, the volume on a radio), the actual amount of power consumed depends on the setting used at any one time. Here are some examples of the range of nameplate wattages for various household appliances:

* Aquarium = 50-1210 Watts
* Clock radio = 10
* Coffee maker = 900-1200
* Clothes washer = 350-500
* Clothes dryer = 1800-5000
* Dishwasher = 1200-2400 (using the drying feature greatly increases energy consumption) 
* Dehumidifier = 785
* Electric blanket - Single/Double = 60 / 100
* Fans
* Ceiling = 65-175
* Window = 55-250
* Furnace = 750
* Whole house = 240-750
* Hair dryer = 1200-1875
* Heater (portable) = 750-1500
* Clothes Iron = 1000-1800
* Microwave oven = 750-1100
* Personal Computer:
* CPU - awake / asleep = 120 / 30 or less
* Monitor - awake / asleep = 150 / 30 or less
* Laptop = 50
* Radio (stereo) = 70-400
* Refrigerator (frost-free, 16 cubic feet) = 725
* Televisions (color):
* 19" = 65-110
* 27" = 113
* 36" = 133
* 53"-61" Projection = 170
* Flat Screen = 120
* Toaster = 800-1400
* Toaster Oven = 1225
* VCR/DVD = 17-21 /20-25
* Vacuum cleaner = 1000-1440
* Water heater (40 gallon) = 4500-5500
* Water pump (deep well) = 250-1100
* Water bed (w/ heater, no cover) = 120-380

Refrigerators, although turned "on" all the time, actually cycle on and off at a rate that depends on a number of factors. These factors include how well it is insulated, room temperature, freezer temperature, how often the door is opened, if the coils are clean, if it is defrosted regularly, and the condition of the door seals. To get an approximate figure for the number of hours that a refrigerator actually operates at its maximum wattage, divide the total time the refrigerator is plugged in by three.

If the wattage is not listed on the appliance, you can still estimate it by finding the current draw (in amperes) and multiplying that by the voltage used by the appliance. Most appliances in the United States use 120 volts. Larger appliances, such as clothes dryers and electric cooktops, use 240 volts. The amperes might be stamped on the unit in place of the wattage. If not, find a clamp-on ammeter, which is an electrician's tool that clamps around one of the two wires on the appliance, to measure the current flowing through it. You can obtain this type of ammeter in stores that sell electrical and electronic equipment. Take a reading while the device is running; this is the actual amount of current being used at that instant. Note: When measuring the current drawn by a motor, in the first second that the motor starts, the meter will show about three times the current than when it is running smoothly.

Also note that many appliances continue to draw a small amount of power when they are switched "off." These "phantom loads" occur in most appliances that use electricity, such as VCRs, televisions, stereos, computers, and kitchen appliances. Most phantom loads will increase the appliance's energy consumption a few watts per hour. These loads can be avoided by unplugging the appliance or using a power strip and using the switch on the power strip to cut all power to the appliance. 




Computer
Fact: By purchasing an Energy Star(r)-compliant computer, monitor, and fax machine, the average home office can cut its energy bill by as much as 45%. You can:
* Cut electricity use 25% per computer. 
* Create a cooler, more comfortable work space. 
* Reduce air-conditioning costs. 

Best Features: Many computers have a built-in feature that automatically powers the unit down to 15% of its maximum power after 15-30 minutes of inactivity. Deep sleep modes offer even greater energy and money savings when the CPU is not in use for 60-70 minutes. Save energy and money by...
* Choosing Energy Star(r)-compliant computers. 
* Ensuring that your computer's power management feature is enabled. 
* Selecting an efficient processor that meets your needs (not necessarily the fastest). 
* Getting a model with an environmental sensor to optimize the power consumption. 

Save Money: Computers without the power-down feature use 25% more electricity. By the same token, the Energy Star(r) label does not guarantee energy savings unless the power management feature is enabled. Operation of the screensaver is not the same as an enabled power management feature. See the user's manual to verify that it is set.
* Use the power management feature, and your equipment will create less heat, thereby lowering your air-conditioning costs.
* Set the shortest possible time that is acceptable before your computer automatically powers down. 
* Turn your computer off at night, on weekends, and when left unused for an extended period. 





Monitor
Fact: Your computer monitor consumes significant amounts of energy even when the screen saver is operating. In fact, more often than not, a screen saver will not only draw power from the monitor, but will also keep the CPU from powering down. You can: 
* Cut energy waste from your monitor by 60-80%. 
* Automatically power down when not in use. 
* Lower your air-conditioning costs resulting from the heat output of your monitor. 

Best Features: Monitors left on around the clock will run up your electric bill, suck in dust, and make your monitor more vulnerable to power surges. Reduce these risks and save energy by... 
* Selecting models with multiple power management features. 
* Choosing a monitor that will automatically return to active mode with a keystroke or mouse click. 
* Get a model with an environmental sensor to optimize the power consumption. 
* Simplify your energy and money-saving choices by choosing an Energy Star(r)-labeled monitor. 

Save Money: A monitor with a power management feature is not a guarantee that your machine is saving energy. It must be enabled. Monitors without the power management option enabled use 60-80% more electricity. Do this: 
* Always check to ensure that the Energy Star(r) features are enabled. 
* Experiment with your delay setting to accomplish the shortest possible time that is acceptable before your monitor automatically goes to sleep or powers down. 
* Turn your monitor off at night, on weekends, and even during the day when it is not being used for an extended period. 

Find It: When you find the Energy Star(r) label on a monitor, you know it has the capability to automatically enter two successive low-power modes. In the first low-power "sleep" mode, the monitor consumes 15 watts or less within 30 minutes of inactivity. If the monitor continues to be idle for a total of 60 minutes, upon instructions from the CPU, it will enter a second low-power "deep sleep" mode where it will consume 8 watts or less. 





Printer
Fact: Printers are typically left on 24 hours a day, but are active only a small percentage of the time--wasting as much as 65% of the electricity consumed by this home office equipment. You can:
* Cut printer electricity consumption by 65%. 
* Produce less heat for a cooler and more comfortable work space. 
* Make your printer last longer. 

Best Features: When choosing or upgrading your printer, select an energy efficient model. It typically has the same or better performance, features, reliability, and price as conventional models, but also saves money and benefits the environment by using less energy. Consider these tips: 
* Buy a printer with duplexing capabilities. 
* Buy a printer-scanner-copier combination to avoid the wasted energy of operating multiple pieces of equipment needlessly. 
* Simplify your purchasing decision by choosing an Energy Star(r)-labeled printer. 

Save Money: Your next purchase will affect your bottom line and the environment for years to come. Choosing a printer with a power-down option may cut the world's energy consumption by only a few watts, but millions of home office equipment purchases and energy-saving actions like those below will make a tremendous impact when added together. 
* Use your printer's power management feature to lessen heat and lower your air-conditioning costs. 
* Set your power-down time on your printer to the shortest acceptable time. 
* Turn off your printer at night, on weekends, and even during the day when unused for an extended time. 
* Look for printers with the double-sided printing option to save money on paper and reduce waste.




TV And VCR
Fact: Americans spend more than $3 billion each year to power their home electronics when they are switched off. Reduce your costs by choosing an energy efficient TV or TV-VCR combination with the Energy Star(r) label. You can:
* Save up to 75% of the energy used when your TV is powered off. 
* Get performance that is equal to or better than similar, conventional models. 
* Reduce carbon dioxide emissions by 110 pounds a year. 

Best Features: Many energy efficient home electronics have the same or better performance, features, reliability, and price as conventional equipment. When you are ready to add, upgrade, or replace your TV, VCR, or TV-VCR combination, remember to choose an Energy Star(r)-labeled TV, VCR, or TV-VCR combination, along with the following... 
* Your TV will use only 3 watts or less of power when switched off, compared to 12 watts of conventional models. 
* Your combination unit will use only 6 watts or less of power when switched off compared to the 20 watts of conventional models. 

Save Money: The energy used to power small household appliances and home electronics like TVs, VCRs, and DVDs is one of the fastest-growing energy loads in the home. Save money by... 
* Unplugging the TV when powered off, if feasible. 
* Buying Energy Star(r) TVs, VCRs, and TV-VCR combinations.




Washer
Fact: The common household clothes washer wastes more energy and money than nearly every other home appliance. You can: 
* Spend 30-75% less on operating costs. 
* Use 50% less water. 
* Cut energy use by 50%. 
* Reduce the environmental and health costs resulting from energy waste. 

Best Features: Choose a clothes washer model with the Energy Star(r) label or a super-efficient model to ensure that you get an appliance with a superior design that requires less water and energy to get clothes thoroughly clean. When shopping for a new washer, look for an ENERGY STAR(r) machine. These machines may cost more to buy but uses about a third of the energy and less water than typical machines. You'll also save more on clothes drying, because most remove more water from your clothes during the spin cycle. Look for machines with... 
* Several options to adjust water level. 
* A minibasket insert that fits over the agitator for smaller loads. 
* Presoaking and/or "suds saver" options, which conserve energy. 
* Faster spin speeds, which remove more water and shorten drying time. 

Save Money: When you are ready to buy a new clothes washer, don't be misled by advertising slogans like Energy Miser, Energy Saver, or Fuel Saver. Instead, choose a clothes washer that uses the least energy to operate. You could save more than $1,000 in energy and water costs over the machine's lifetime. With savings like that, the machine will pay for itself even if the initial cost is higher than the less efficient models. 




Dryer
Fact: The clothes dryer uses more electricity than every appliance after the washing machine and refrigerator. You can:
* Use 15% less energy. 
* Be gentle on your clothes and avoid over drying. 

Best Features: New dryers aren't required to display Energy Guide labels, which makes it hard to compare the energy efficiency of different models in the showroom. In selecting your dryer, look for an appliance that... 
* Removes moisture more efficiently. 
* Has moisture sensors. 
* Has automatic shut-off controls to avoid over drying. 

Save Money: Dryers work by heating and aerating clothes. The efficiency of a clothes dryer is measured by a term called the energy factor. Energy efficient dryers take less money to operate, and can actually produce cleaner, fresher clothes. 

When shopping for a new clothes dryer, look for one with a moisture sensor that automatically shuts off the machine when your clothes are dry. Not only will this save energy, it will save wear and tear on your clothes caused by over-drying. Keep in mind that gas dryers are less expensive to operate than electric dryers. 




Laundry Tips
Here are some tips to help you save money: 
* Locate the dryer in a heated space so it doesn't have to work as hard. 
* Use the straightest and shortest metal duct available to you. 
* Replace the outside dryer exhaust vent if it doesn't close. 
* Clean the lint filter in the dryer after every load to improve air circulation. 
* Dry similar types of clothes together to reduce energy use. 
* Dry two or more loads in a row, taking advantage of the dryer's retained heat.
* Use hot water only for very dirty loads. 
* Always use cold water during the rinse cycle to cut a load's energy use in half.
* Wash your clothes in cold water using cold-water detergents when-ever possible.
* Wash and dry only full loads of clothes, and set the water level appropriately. 
* Use the right amount of detergent to avoid having to wash or rinse the load again. 
* Select the best cycle for the soil level to prevent over washing clothes and inefficient use of the appliance. 
* Presoak or use a soak cycle when washing heavily soiled garments to avoid two washings and save energy.
* About 80% to 85% of the energy used for washing clothes is for heating the water. There are two ways to reduce the amount of energy used for washing clothes-use less water and use cooler water. Unless you're dealing with oily stains, the warm or cold water setting on your machine will generally do a good job of cleaning your clothes. Switching your temperature setting from hot to warm can cut a load's energy use in half.
* Dry towels and heavier cottons in a separate load from lighter-weight clothes.
* Don't over-dry your clothes. If your machine has a moisture sensor, use it.
* Use the cool-down cycle to allow the clothes to finish drying with the residual heat in the dryer.
* Periodically inspect your dryer vent to ensure it is not blocked. This will save energy and may prevent a fire. Manufacturers recommend using rigid venting material, not plastic vents that may collapse and cause blockages.
* Look for the ENERGY STAR(r) and EnergyGuide labels.




Oven
Fact: Cooking food and washing dishes accounts for about 10% of all energy used in the home. You can: 
* Use up to 30% less energy. 
* Cut your operating costs up to 50%. 

Best Features: Choosing a gas oven/range with an electronic ignition instead of a pilot light will cost you half as much to operate as an electric oven/range. If you're in the market for new appliances, by choosing wisely among the latest models with these features, you can increase your kitchen's energy efficiency. 
* Consider buying a self-cleaning oven. Its higher insulation levels result in lower energy use. 
* Buy a gas oven with the new electronic pilotless ignition to reduce gas usage by about 30% over a constantly burning pilot light. 
* Buy an electric oven with halogen and/or induction elements, which use less energy than conventional electric coil elements. 

Save Money: Cooking with natural gas is cheaper than cooking with electricity, if you have the choice. If you're using electricity, however, get in the habit of turning off the burners and oven several minutes before the end of the allotted cooking time. The heating element will stay hot long enough to finish the cooking without using more electricity. Try these money-saving steps for a gas or electric oven/range: 
* Preheat ovens only when necessary. 
* Don't lay foils on racks. 
* Use glass or ceramic pans in ovens. 
* Keep range-top burners and reflectors clean. 
* Match the size of the pan to the heating element (use a small pan on a small burner). 
* Use smaller kitchen appliances instead of your oven/range when appropriate. 
* When boiling water in a pan, always use a cover. 
* Bake several items at the same time when using your oven.




Dishwasher
Fact: A dishwasher typically uses the equivalent of 700-850 kilowatt-hours of electricity annually, or nearly as much energy as a clothes dryer or freezer. About 80% of this energy is used, not to run the machine, but to heat the water for washing the dishes. You can:
* Use 50% less electricity when running your dishwasher. 
* Cut your water consumption in half on every load. 

Best Features: The most water-efficient dishwashers currently on the market use about 5 gallons of hot water per load, or less than half as much as the least efficient ones. When buying a dishwasher...
* Compare annual operation costs shown on the Energy Guide label. 
* Choose a model with several different wash cycle selections. 
* Look for an option for heat-drying and air-drying. 
* Opt for a feature that senses how dirty the dishes are and runs appropriate cleaning cycles. 
* Get a multiple-level wash system. 
* Select a dishwasher with a thermostat and heating capability. 

Save Money: Buying the correct size appliance for your needs is critical to saving money, energy, and water. In dishwashers, there are compact and standard-capacity units. Compact models use less energy and water per load, so you may actually consume more energy operating them more frequently. The EnergyGuide label estimates how much power is needed per year to run the appliance and to heat the water based on the yearly cost of gas and electric water heating. When it is time to buy a new unit, look for the ENERGY STAR(r) label.




Dishwasher Tips
Check the manual that came with your dishwasher for the manufacturer's recommendations on water temperature; many have internal heating elements that allow you to set the water heater to a lower temperature. The following tips help you to save even more:
* Avoid rinsing dishes before you load them in the dishwasher or, if you must rinse, use cold water. 
* Always operate a dishwasher with a full load. If this isn't possible, use an energy-saving cycle. 
* Select the no heat-drying option, if your machine has it. If not, stop the machine before the drying cycle begins, and open the door to let dishes air-dry.
* Scrape, don't rinse, off large food pieces and bones. Soaking or prewashing is generally only recommended in cases of burned-on or dried-on food.
* Be sure your dishwasher is full, but not overloaded.
* Don't use the "rinse hold" on your machine for just a few soiled dishes. It uses 3 to 7 gallons of hot water each time you use it.
* Let your dishes air dry; if you don't have an automatic air-dry switch, turn off the control knob after the final rinse and prop the door open a little so the dishes will dry faster.




Refrigerator
Fact: Refrigerators are the single biggest power drains in most households--accounting for 9-25% of a household's total energy consumption! A typical refrigerator made around 1990 uses about 900 kilowatt-hours per year. You can: 
* Use 20-50% less energy. 
* Reduce indoor noise. 
* Help the environment. 

Best Features: Look for the Energy Guide label to see how much electricity, in kilowatt-hours (kWh), the refrigerator or freezer will use in one year. The smaller the number, the less energy it will use. In addition to the EnergyGuide label, don't forget to look for the ENERGY STAR(r) label. A new refrigerator with an ENERGY STAR(r) label will save you money. This adds up during the average 15-year life of the unit. When purchasing your appliance, look for the following: 
* Energy Star(r)-labeled units because they exceed Federal standards by at least 20%. 
* Top freezer models because they use 7-13% less energy than side-by-side models. 
* 16-20 cubic foot size (maximum energy efficient models). 
* Models without automatic icemakers and through-the-door dispensers because these features increase energy use by 14-20% and add $750-250 to the purchase price. 
* Models that do not have an antisweat heater unless you want to consume 5-10% more energy. 




Refrigerator/Freezer Energy Tips
* Look for a refrigerator with automatic moisture control. Models with this feature have been engineered to prevent moisture accumulation on the cabinet exterior without the addition of a heater. This is not the same thing as an "anti-sweat" heater. Models with an anti-sweat heater will consume 5% to 10% more energy than models without this feature.
* Don't keep your refrigerator or freezer too cold. Recommended temperatures are 37° to 40°F for the fresh food compartment of the refrigerator and 5°F for the freezer section. If you have a separate freezer for long-term storage, it should be kept at 0°F.
* To check refrigerator temperature, place an appliance thermometer in a glass of water in the center of the refrigerator. Read it after 24 hours. To check the freezer temperature, place a thermometer between frozen packages. Read it after 24 hours.
* Regularly defrost manual-defrost refrigerators and freezers; frost buildup increases the amount of energy needed to keep the motor running. Don't allow frost to build up more than one-quarter of an inch.
* Make sure your refrigerator door seals are airtight. Test them by closing the door over a piece of paper or a dollar bill so it is half in and half out of the refrigerator. If you can pull the paper or bill out easily, the latch may need adjustment or the seal may need replacing.
* Cover liquids and wrap foods stored in the refrigerator. Uncovered foods release moisture and make the compressor work harder.
* Move your refrigerator out from the wall and vacuum its condenser coils once a year unless you have a no-clean condenser model. Your refrigerator will run for shorter periods with clean coils.
* Refrigerators with the freezer on top are more efficient than those with freezers on the side.
* Operating one large refrigerator/freezer is less costly than operating two smaller refrigerators/freezers. You can save more money if you... 
* Replace a refrigerator that is 15 years or older with a new, more efficient unit. 
* Keep the doors closed as much as possible, and make sure they are closed tightly. 
* Avoid overcrowding, because too many items obstruct air circulation and reduce cooling capabilities. 




Other Energy-Saving Kitchen Tips
* Be sure to place the faucet lever on the kitchen sink in the cold position when using small amounts of water; placing the lever in the hot position uses energy to heat the water even though it never reaches the faucet.
* If you need to purchase a gas oven or range, look for one with an automatic, electric ignition system. An electric ignition saves gas-because a pilot light is not burning continuously.
* In gas appliances, look for blue flames; yellow flames indicate the gas is burning inefficiently and an adjustment may be needed. Consult your manufacturer or your local utility.
* Keep range-top burners and reflectors clean; they will reflect the heat better, and you will save energy.
* Use a covered kettle or pan to boil water; it's faster and it uses less energy.
* Match the size of the pan to the heating element.
* If you cook with electricity, turn the stovetop burners off several minutes before the allotted cooking time. The heating element will stay hot long enough to finish the cooking without using more electricity. The same principle applies to oven cooking.
* Use small electric pans or toaster ovens for small meals rather than your large stove or oven. A toaster oven uses a third to half as much energy as a full-sized oven.
* Use pressure cookers and microwave ovens whenever it is convenient to do so. They can save energy by significantly reducing cooking time.





Combustion Appliance Safety Tips
Combustion appliances using natural gas, propane, oil, kerosene, or wood are often a more efficient and cost-effective way to produce heat than electricity. Examples include: 
* Furnaces
* Space heaters
* Fireplaces
* Wood stoves
* Water heaters
* Range tops
* Ovens
* Clothes dryers

Combustion appliances have been used for many years in millions of homes. However, careful installation and maintenance of each unit is required to ensure safe and efficient operation, especially in today's energy-efficient, tightly sealed homes.

Problems Posed by Combustion Equipment: Combustion appliances burn fuel by using oxygen from supply air. They produce exhaust gases that should be directly vented to the outside to avoid introducing combustion by-products into the house. Exhaust gases may be released inside the house either knowingly-as in the case of unvented stoves, ovens, fireplaces, or space heaters-or unknowingly from leaky flues, cracked heat exchangers, or back-drafting. Three components of exhaust gases are especially troublesome when introduced indoors: carbon monoxide, water vapor, and nitrogen oxides.

Carbon monoxide (CO) is a toxic gas that is colorless, tasteless, and odorless. It can cause serious medical problems and is the cause of hundreds of deaths in U.S. homes each year!! CO is produced when insufficient combustion air is supplied to the appliance, the burner is improperly tuned, and/or the appliance is malfunctioning. See Figure 12.

Water vapor is present in large amounts in exhaust gases as a result of burning all fuels. When water vapor is introduced into a house, it increases humidity levels and can lead to condensation on window panes, exterior walls, and interior surfaces of wall cavities. High humidity and wet surfaces promote mold growth, wood deterioration, and other health and structural problems. Nitrogen oxides are usually present only in small amounts in exhaust gases, but they still present a health hazard to the inhabitants.

All combustion appliances should be installed by knowledgeable technicians according to the manufacturer's installation instructions as well as following all national and local code requirements. As part of the installation process, CO measurements should be made to ensure the proper operation of the units and the safety and health of the occupants. CO should be measured in the combustion products of furnaces and water heaters before the diverter or before dilution occurs, and after the burner has run continuously for 5 minutes. Levels greater than 100 ppm (air free rather than as tested) indicate adjustments are necessary; levels less than 10 ppm usually are readily achievable. Ovens should be tested while operating on the BAKE setting, and range tops should be tested with a water-filled pan over the burner. CO levels greater than 50 ppm (air free) are not acceptable.

Install a Carbon Monoxide Detector: CO detectors are highly recommended in homes with fuel-burning appliances. The detectors signal homeowners via an audible alarm when CO levels reach potentially dangerous levels. Some models have digital readouts of current CO levels, which are useful to the homeowner to monitor household air quality, while some less-expensive models indicate varying levels of CO with differing alarms. CO detectors are either plug in or hard-wired. They should be installed in rooms with a direct connection to combustion appliances, such as kitchens with fuel-burning stoves or ovens, areas near combustion closets for fuel burning heating systems, and rooms with fuel-burning space heaters.

Causes of Back-Drafting: Back-drafting occurs when combustion gases are pulled down the exhaust flue and into the house rather than being vented to the outside. Appliances with atmospheric vents rather than powered combustion systems are most susceptible to back-drafting. Clothes dryers, ventilation fans in bathrooms and kitchens, and whole-house fans are examples of household equipment that can reduce the air pressure surrounding the combustion appliance to levels that cause it to back-draft. The potential for back-drafting increases the closer the fan is to the appliance, when several fans run simultaneously, and when the appliance cannot be isolated from the fan through the use of a closed door or other means.

Leaks in heating and cooling ducts or poorly designed ductwork can also be a major cause of back-drafting. Leaks in supply ducts can create a negative pressure in the house (the pressure in the house is less than outside) because less air is being returned to the house through the supply ducts than is being removed from the house by the return ducts. If this negative pressure is large enough, it can prevent combustion gases from rising up the flue and cause combustion products to spill into the house.

A return register that is too close to the combustion appliance (especially if it is the only return register in the house) can create a negative pressure around the appliance that draws exhaust gases into the house. A leak in a return duct or return plenum that allows air surrounding the appliances to be drawn into the return system creates a similar effect.

Negative pressures can also be created in the main part of a house, where the combustion appliance often is located, when interior doors are closed. This can occur especially when there are only one or two return registers in the house and even in homes with tight ductwork. When the doors to rooms with supply registers are closed, it may be difficult for the air in these rooms to circulate back to a central return register. The pressure in the closed-off room increases, and the pressure decreases in the main part of the house open to the central return.

Preventing Back-Drafting: The potential for back-drafting can be reduced by:
* Using appliances with powered combustion systems rather than atmospheric vents. 
* Installing appliances with atmospheric vents in a sealed combustion closet.
* Sealing all supply and return duct leaks.
* Installing return registers in all rooms with supply registers.
* Making sure rooms without a return register have at least a 1-inch gap under the door (recommended only for rooms with one supply register) or a transfer grill to provide pressure equalization between rooms.