The links below provide an outline of the material for this lesson. Be sure to carefully read through the entire lesson before returning to Canvas to submit your assignments.
Welcome to the Appliances lesson! This is the most important one for most students--most important in the sense that it can make a difference in both energy consumption and environmental protection because we use a lot of appliances at home. We use a lot of energy for these appliances. In this chapter we are going to learn the basic operating principles of most of the residential big ticket items, for example refrigerators, or water heaters. Water heaters are one of the most energy-consuming appliances. And we will talk about clothes washers and dryers. We are not going to look at how to do the laundry, but we are going to look at the basic operating principles. In other words, how these things really operate. What are all the things that govern energy consumption, and what are all the things we need to look for when we buy some of these appliances?
We'll also learn how to do a cost benefit analysis. To do that, we will learn how to read energy guide labels. Energy guide labels are the yellow, ugly looking labels on appliances that give you the amount of energy that a model consumes. So when you go shopping (I'm sure you are all going to do that with your significant others in a few years) you're going to compare different options. You are going to look at a couple of models -- 3, 4 or 5 models, and say, "Okay, this is better than this; this is worse than this," and so on.
What are the factors that go into comparing several models and picking the right one, both with respect to energy consumption and environment protection? I will show you what kind of information you can get from these energy guides and how these can be used to compare model A vs. model B. For example, model A may cost $1000 and Model B may cost $1500. What you are basically deciding is, is it worth it to pay $500 extra to get the benefits that this model will give? In other words, the more expensive model obviously "should" give you more features that you want, or it should give you energy savings in the long run -- for example, cutting your energy bill by $50 every month. So it's going to really take about 10 months to recover the $500 you are paying up front. This kind of analysis is basically called life cycle analysis--what it would cost to buy a piece of equipment and to operate that over its lifetime. And we do that calculation for two models and see, in the long run, that one model is going to be cheaper and environmentally friendlier than another model. So we are going to learn how to do that. That discussion will be very common for all the appliances, and this calculation of payback period is the key for most of this lesson as well as the lessons to come. We will also look at refrigerators and calculate the efficiency of these refrigerators and how to use the efficiency we need to calculate how much energy these things consume. We will do that with clothes washers and dryers.
From here on you will also encounter some acronyms and energy efficiency terms, so you will need to pay attention to those. And, as I told you, these calculations and the use of the energy guides are the most important concepts in this lesson.
Upon completing this lesson, you should be able to:
If you have any questions, please post them to the General Course Questions forum in located in the Discussions tab in Canvas. I will check that discussion forum daily to respond. While you are visiting the discussion board, feel free to post your own responses to questions posted by others - this way, you might help a classmate!
Most homes have a variety of appliances with a wide range of operating costs. Typical costs of operation of basic household appliances are shown in the graph below.
Household appliances, cooking, and lighting consume 33% of the energy at home as shown in the pie chart below. Water heating (not included in the appliances) is the second largest energy expense after home heating and cooling. It typically accounts for about 14% of the utility bill.
All major home appliances must meet the Appliance Standards Program set by the US Department of Energy (DOE). Manufacturers must use standard test procedures developed by DOE to prove the energy use and efficiency of their products. Test results are printed on yellow Energy Guide labels (pictured below) which manufacturers are required to display on many appliances. This label provides the necessary information to perform a Life Cycle Analysis when comparing different models.
Instructions: View detailed descriptions about the information found on Energy Guide labels.
The Federal Trade Commission's Appliance Labeling Rule requires appliance manufacturers to put these labels on refrigerators, freezers, dishwashers, clothes washers, water heaters, furnaces, boilers, central air conditioners, room air conditioners, heat pumps, and pool heaters. The law requires that the labels specify:
A worksheet on how to use the labels in choosing a cost-effective and environmentally friendly appliance is given below.
Part A - General Information | |
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1. Are the appliances comparable in size and features? | Answer has to be yes |
2. What is the price of the more energy- efficient model? | $ ________ |
3. What is the price of the less energy-efficient model? | $ ________ |
4. What is the price of electricity in your region? | $ ________ / kWh |
5. How long do you expect to keep the appliance? What is the life of the Appliance? | ________ |
PART B - Determining why you should buy an energy efficient model | |
1. Calculating the price difference: | |
2. Price of the more energy-efficient model | $ ________ |
3. Price of the less energy-efficient model | $ ________ |
4. Price Difference | $ ________ |
Determining the annual energy savings | |
1. Annual energy consumption of the less energy-efficient model | ________ kWh |
2. Annual energy consumption of the more energy-efficient model | ________ kWh |
3. Annual energy savings | ________ kWh |
Determining the savings | |
1. Annual energy savings | ________ kWh |
2. Annual monetary savings on energy (energy savings x price) | $ ________ |
3. Energy savings over the life time of the appliance | ________ kWh |
(Life in years x annual energy savings) | |
1. Cost of energy savings over life time of the appliance | $ ________ |
Determining the Pay Back Period | |
1. Price difference between the models | $ ________ |
2. Annual monetary savings on energy (energy savings x price) | $ ________ |
3. Pay Back Period (years to recover the additional investment ) | $ ________ |
4. Monetary savings on energy over the lifetime | $ ________ |
5. Price Difference | $ ________ |
6. Total monetary benefit for choosing environmentally friendly appliance (4 – 5) | $ ________ |
Heat is continuously flowing from the tank of the water heater and the pipes to the room because the water heater is always at a higher temperature than the surroundings (basement or garage). Thermal energy flows from high temperature to low temperature. Heat is lost whether you use water or not.
Like most appliances, water heaters have improved greatly in recent years. Today's models are much more energy efficient, and you will be able to purchase a more efficient water heater that will save you money on energy each month. The average life expectancy of a water heater is 13 years. Therefore, the initial purchase price should not be an important factor in selecting a water heater.
Just like other appliances, there are two costs associated with water heaters - initial purchase price and operating costs. Water heaters typically last for about 13 years, after which they need to be replaced. Also, each month, you pay for the fuel you use. An energy-efficient model could save hundreds of dollars in the long run in the energy costs and may offset the higher initial purchase price.
It can be compared to automobile mileage—some cars get 15 miles to a gallon, while other, more efficient, vehicles can go 30 miles or more on a gallon of gas. In the same way, some water heaters use energy more efficiently.
One should buy an energy-efficient water heater and spend less money each month to get the same amount of hot water.
The table below shows typical water use for various purposes at home.
Use | Gallons per use |
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Shower | 7-10 |
Bath (standard tub) | 20 |
Bath (whirlpool tub) | 35-50 |
Clothes washer (hot water wash, warm rinse) | 32 |
Clothes washer (warm wash, cold rinse) | 7 |
Automatic dishwasher | 8-10 |
Food preparation and cleanup | 5 |
Personal (hand-washing, etc.) | 2 |
Energy costs increase with water temperature. Dishwashers require the hottest water of all household uses, typically 135ºF to 140ºF. However, these devices are usually equipped with booster heaters to increase the incoming water temperature by 15ºF to 20ºF. Setting the water heater between 120ºF and 125ºF and turning the dishwasher’s booster on should provide sufficiently hot water while reducing the chances for scalding.
The amount of energy required to heat water is proportional to the temperature difference of what?
To calculate the Heat Required, use this equation:
Where …
= mass of water heated
= the heat capacity of water (1 BTU / lb ºF)
= temperature difference.
It is estimated by the United States Department of Energy that a family of four, each showering for 10 minutes a day, consumes about 700 gal of hot water a week. Water for the showers comes into the home at 55ºF and needs to be heated to 120ºF.
To calculate the heat required, determine the variables:
m = mass of water heated = 700 gallons = 5810 lbs
Cp is the heat capacity of water = 1 BTU/lb ºF (given)
ΔT = temperature difference = 120 ºF – 55 ºF
Heat energy required to heat 700 gal can be calculated as follows:
Heat Required = 5810 lbs x 1 BTU/lb ºF x (120 ºF – 55 ºF)
Heat Required = 5810 lbs x 65 ºF
Heat Required = 377,650 BTU/week
The heat requirement for one year is :
377,650 BTU/Week x 52 Weeks/Year = 19,637,800 BTU/year or 5,755 kWh
Assuming that the natural gas costs $ 10/MMBTU (1 MMBTU = 1000000 BTU) and electricity costs 0.092 per kWh, the gas costs would be $196.37 while electric costs would be $529.46. Clearly, electric heat is more expensive than natural gas.
Estimate the % energy savings of an electric water heater that heats 100 gallons of per day when the temperature is set back at 110° instead of 120°F. The basement is heated and is at 65°F. The life of the water heater is expected to be about 10 years. Use an appropriate cost for electricity and compare the operating expenses.
Heat required (BTU) = m x Cp x (Temperature Difference)
Where Cp is the heat capacity of water (1 BTU/lb/F) and m is the mass of the water (Assume 1 gal has 8.3 lb of water and the 3,412 BTU = 1 kWh)
Solution:
Energy required for heating the water to 120°F:
In a year the energy required is:
In a 10-year period, the energy required is 166,622,500 BTU which is equal to 48,834 kWh.
Operating cost over its lifetime is:
Energy required for heating the water to 110°F:
In a year, the energy required is:
In a 10-year period, the energy required is 136,327,500 BTU which is equal to 39,995 kWh .
Operating cost over its lifetime is:
Estimated % Energy Savings:
There are several types of water heaters that are available on the market:
However, most water heaters use a storage tank type.
Storage or tank-type water heaters are relatively simple devices and by far the most common type of residential water heater used in the United States. They range in size from 20 to 80 gallons, and can be fueled by electricity, natural gas, propane, or oil.
When you turn on a hot water faucet or use hot water in a dishwasher or clothes washer, water pipes draw hot water from the tank. To replace that hot water, cold water enters the bottom of the tank, ensuring that the tank is always full. Depending on the type of fuel that is used, either electrical heating elements or a natural gas burner is used to heat the water.
Click the “play” button on the animation below to see how a gas hot water heater works.
Electric water heaters are generally less expensive to install (purchase price) than gas-fired types because they don't require gas lines and vents to let the combustion products out of the house. In previous lessons, and in Home Activity 2, we have seen that natural gas costs about 7–12 dollars per million BTUs, whereas electrical energy is 20–25 dollars per million BTUs, making electric water heaters more expensive to operate.
Storage tank-type water heaters raise and maintain the water temperature to the temperature setting on the tank (usually between 120°–140°F). Because the water is constantly heated and kept ready for use in the tank, heat energy can be lost even when no faucet is on. This is called standby heat loss. These standby losses represent 10 to 20 percent of a household's annual water heating costs. Newer, more energy-efficient storage models can significantly reduce the amount of standby heat loss, making them much less expensive to operate.
Demand Water Heaters do not have storage tanks, so there is no standby heat loss from the tank, and energy consumption is reduced by 20 to 30 percent. Demand water heaters are available in propane (LP), natural gas, or electric models.
In these types of water heaters, cold water travels through a pipe into the unit, and either a gas burner or an electric element heats the water only when needed. With these systems, you never run out of hot water. However, the flow rate is limited by the outlet temperature.
The appeal of demand water heaters is the elimination of the tank standby losses, the resulting lower operating costs, and the fact that the heater delivers hot water continuously.
Click the “play” button to see how a Demand Water Heater works.
Typically, demand heaters provide hot water at a rate of 2 to 4 gallons per minute. This flow rate might meet the requirements of a household's hot water needs as long as the hot water is not needed in more than one location at a time (e.g., one cannot shower and do the laundry simultaneously). To meet hot water demand when multiple faucets are being used, demand heaters can be installed in parallel sequence.
Although gas-fired demand heaters tend to have higher flow rates than electric ones, they can waste energy even when no water is being heated if their pilot lights stay on. However, the amount of energy consumed by a pilot light is quite small. Thus, in most cases, gas demand water heaters will cost less to operate than electric water heaters.
Demand water heaters cost more than conventional storage tank-type units. Small point-of-use heaters that deliver 1 to 2 gallons per minute (gpm) sell for about $200. Larger gas−fired demand units that deliver 3 to 5gpm cost $550 - $1,000. The more hot water the unit produces, the higher the cost.
Advantages | Disadvantages |
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An estimated one million residential and 200,000 commercial solar water-heating systems have been installed in the United States. Although there are a large number of different types of solar water-heating systems, the basic technology is very simple.
Sunlight strikes and heats an "absorber" surface within a "solar collector" or an actual storage tank. These roof-mounted solar heaters supply about 80% of the hot water for the home. Either a heat-transfer fluid or the actual potable water to be used flows through tubes attached to the absorber and picks up the heat from it. (Systems with a separate heat-transfer-fluid loop include a heat exchanger that then heats the potable water.) The heated water is stored in a separate preheat tank or a conventional water heater tank until needed.
If additional heat is needed, it is provided by electricity or fossil-fuel energy by the conventional water-heating system.
Click the “play” button to see how a solar water heater operates.
By reducing the amount of heat that must be provided by conventional water heating, solar water-heating systems directly substitute renewable energy for conventional energy, reducing the use of electricity or fossil fuels by as much as 80%.
Today's solar water-heating systems are proven reliable when correctly matched to climate and load. The current market consists of a relatively small number of manufacturers and installers that provide reliable equipment and quality system design.
A quality assurance and performance-rating program for solar water-heating systems, instituted by a voluntary association of the solar industry and various consumer groups, makes it easier to select reliable equipment with confidence.
Building owners should investigate installing solar hot water-heating systems to reduce energy use. However, before sizing a solar system, water-use reduction strategies should be put into practice.
There are five types of solar hot water systems:
Direct-circulation, thermosiphon, or pump-activated systems require higher maintenance in freezing climates. For most of the United States, indirect air and water systems are the most appropriate. Air solar systems, while not as efficient as water systems, should be considered if maintenance is a primary concern since they do not leak or burst.
Heat pumps are a well-established technology for space heating. The same principle of transferring heat is at work in heat pump water heaters (HPWHs) except that they extract heat from air (indoor, exhaust, or outdoor air) and deliver it to water. Some models come as a complete package, including tank and back-up resistance heating elements, while others work as an adjunct to a conventional water heater.
The simplest HPWH is the ambient air-source unit, which removes heat from surrounding air, providing the additional benefit of space cooling. Exhaust air units extract heat from a continuously exhausted air stream and work better in heating-dominated climates because they do not cool ambient air. Some units can even be converted between the two modes of operation for optimum operation in either summer or winter.
In mild climates, you can place ambient air-source units in unheated but protected spaces such as garages, essentially using outdoor air as a heat source.
Because it extracts heat from air, the HPWH delivers about twice the heat for the same electricity cost as a conventional electric resistance water heater.
The Desuperheater feature is available on some central air conditioners and is a variation of the stand-alone HPWH. It provides economical supplemental water heating as a byproduct of air conditioning.
Desuperheater water heating can be part of an integrated package with a heat pump or air conditioner system. In most such systems, the heat pump water heating only occurs during normal demand for space conditioning, with resistance electric coils providing water heating the rest of the time.
During the cooling season, the Desuperheater actually improves the efficiency of the air conditioning system while heating water at no direct cost. In an average climate, a desuperheater might meet 20 to 40 percent of annual water heating demand.
Heat pump water heaters can provide up to 60 percent energy savings over conventional water heaters.
The HPWH consists of three circuits. The HPWH consists of three circuits. Watch the video below to learn more about how a HPWH works.
Note: The concept shown in the animation is applicable to all HPWH: heat is picked up and delivered into some source – which could either be the ground, air, or water.
Most of the heat delivered to the water comes from the evaporator of the unit, not through the electrical input to the machine. Consequently, the efficiency of the HPWH is much higher than for direct-fired gas or electric storage water heaters.
The installed cost of commercial HPWH systems is typically several times that of gas or electric water heaters; yet the low operating costs can often offset the higher total installed cost, making the HPWH the economic choice for water heating.
The HPWH becomes increasingly attractive in building applications where energy costs are high, and where there is a steady demand for hot water. This attractiveness is less a function of building type than it is of water demand and utility cost.
The federal efficiency standards for water heaters took effect in 1990, assuring consumers that all new water heaters meet certain minimum-efficiency levels. New standards, which took effect in January 2004, will increase the minimum efficiency levels of these products.
Water heater efficiency is reported in terms of the energy factor (EF). EF is an efficiency ratio of the energy supplied in heated water divided by the energy input to the water heater, and it is based on recovery efficiency, standby losses, and cycling losses. The higher the EF, the more efficient the water heater.
There is little difference between the most efficient electric resistance storage water heaters and the minimum-efficiency standard that will take effect in January 2004. If you need to rely on electricity to heat your water, keep your eye out for the further development of heat-pump water heaters. This technology uses one-third to one-half as much electricity as a conventional electric resistance water heater.
Everything else being equal, select a water heater with the highest energy factor (EF). Below is a table with energy efficiency recommendations.
Storage Type | Recommended | Best Available | ||
---|---|---|---|---|
Energy Factor | Annual Energy Use (kWh) | Energy Factor | Annual Energy Use (kWh) | |
Less than 60 gallons | 0.93 | 4,721 | 0.95 | 4,622 |
60 gallons or more | 0.91 | 4,825 | 0.92 | 4,773 |
The higher the EF, the more efficient the water heater.
In addition to EF, also look for a water heater with at least one-and-a-half inches of tank insulation and a heat trap.
In addition, capacity of a water heater is an important consideration. The water heater should provide enough hot water at the busiest time of the day. For example, a household of two adults may never use more than 30 gallons of hot water in an hour, but a family of six may use as much as 70 gallons in an hour.
The ability of a water heater to meet peak demands for hot water is indicated by its "first hour rating." This rating accounts for the effects of tank size and the speed by which cold water is heated. Water heaters must be sized properly. Over-sized water heaters not only cost more but increase energy use due to excessive cycling and higher standby losses.
Let’s use the Energy Guide to perform a life-cycle analysis to help choose a water heater. Different models of water heaters with the same capacity can vary dramatically in the amount of electricity they use.
Text description of the Life Cycle Analysis activity. [5]
Instructions: Use the two EnergyGuide Labels for the different water heaters, to answer questions 1-8.
Click here to open a text description comparing the two EnergyGuide Labels.
Water Heater #1:
Water Heater #2:
Still trying to figure out the payback period? The price difference between the two models was $45, and your annual monetary savings was $33.76. So after one year, you got back $33.76 out of the $45 extra you spent on the superior model. How much longer would it take you to get back the remaining $11.24? Since $11.24 is about a third of $33.76, it would take you about a third of a year. Thus, your payback period is 1.33 years.
Obviously, it pays to buy an energy-efficient water heater by saving $393.96. It also helps the environment by not using 4,771 kWh of electrical energy and thereby not emitting 9,652 lb of CO2, 21 lb of NOx, 75 lb of SO2 and 1 lb of CO and particulate matter each and into the environment. See the individual’s power!
Refrigerators are heat movers, which move heat from a low temperature (inside the refrigerator) to a high temperature (outside the refrigerator into the kitchen). Heat movers do not produce any heat, but just move from one location to another. (Note: The animation has no audio.)
The principle of operation of a refrigerator is similar to an air conditioner. It moves the heat energy from inside to outside. There are four basic components in a refrigerator and their functions are as follows:
Click the “play” button to learn how a refrigerator works.
Click here to open a text description of how a refrigerator works.
Compressed liquid refrigerant passes through an expansion valve that reduces the pressure and, in turn, the temperature. The now cold liquid travels through a series of evaporator coils. As it travels through the coils, the liquid evaporates, drawing the heat energy needed for evaporation from the food in the fridge. This process leaves the food cold as the heat has been moved to the refrigerant.
The evaporated refrigerant passes through a compressor that raises the pressure and temperature of the refrigerant and turns it back into a liquid. The liquid dispenses the heat collected from inside the fridge through the condenser coils and then passes through the expansion valve again to repeat the process.
There are four types of refrigerators: top-freezer (or top-mount), bottom-freezer (or bottom-mount), side-by-side, and built-in (as shown below).
Refrigerators also come in four size categories: small (7 to 9.9 cubic feet), medium (10 to 13.9 cubic feet), large (14 to 19.9 cubic feet), and extra large (20 to 29 cubic feet).
Most of the energy used by a refrigerator is used to pump heat out of the cabinet. A small amount is used to keep the cabinet from sweating, to defrost the refrigerator, and to illuminate the interior.
The efficiency of a refrigerator is based on the energy consumed per year for a given size. The efficiency of a refrigerator is expressed in volume cooled per unit electric energy per day. Volume is measured in cubic feet and electrical energy is measured in kilowatt-hours.
Refrigerator Efficiency = Volume Cooled (ft3) / Unit Electrical Energy per day (KWh)
The energy efficiency of refrigerators and freezers has improved dramatically over the past three decades. For example, the energy bill for a typical new refrigerator with automatic defrost and top-mounted freezer will be about 55 dollars / year, whereas a typical model sold in 1973 will cost nearly 160 dollars / year (almost three times the energy consumption).
The Department of Energy (DOE) standards set maximum allowable annual energy consumption for different sizes and classes of refrigerators. These Federal efficiency standards first took effect in 1993, requiring new refrigerators and freezers to be more efficient than ever before. A new set of stricter standards took effect July 1, 2001.
Refrigerators now come with an EnergyGuide label that tells you in kilowatt-hours (kWh) how much electricity a particular model uses in a year. The smaller the number, the less energy the refrigerator uses and the less it will cost you to operate.
ENERGY STAR qualified refrigerators provide energy savings without sacrificing the features you want. ENERGY STAR–qualified models have
These models also use at least 15% less energy than required by current federal standards, and 40% less energy than the conventional models sold in 2001.
Many ENERGY STAR qualified models include automatic ice-maker and through-the-door ice dispensers. Qualified models are also available with top, bottom, and side-by-side freezers.
When selecting a refrigerator, remember the following:
The improvement in the energy efficiency over the past three decades is due to the:
Clothes washers and dryers account for 10 percent of the residential energy consumption, with most of the energy consumed for hot water used for washing.
A typical household does nearly 400 loads of laundry a year, and each load in a conventional washer uses 40 gallons of water. Therefore, any reduction in energy consumption for clothes washing application would involve reduction in hot water use.
The basic principle for cleaning clothes has remained unchanged—wet the garment, agitate it to loosen the dirt from the cloth fibers, and then use more water to rinse the dirt off. What has changed over the millennia is the method of agitation? Pounding garments with stones was common for several thousand years, and along the way someone also figured out that using heated water got out a lot more dirt.
Clothes washers come in two types: Horizontal axis (h-axis) or front loading and Vertical axis (v-axis) or top loading (shown below).
Most clothes washers produced for the U.S. consumer are vertical axis (v-axis) washers with a central agitator. While there are variations, most v-axis washers suspend the clothes in a tub of water for washing and rinsing.
As an alternative, the horizontal axis (h-axis) washer tumbles the wash load repeatedly through a small pool of water at the bottom of the tub to produce the needed agitation. This tends to reduce the need for both hot and cold water.
The h-axis washer, popular in Europe, has a very limited market share in the United States at present. Yet, estimates have shown that a large quantity of energy and water could be saved through the replacement of conventional v-axis washers with the h-axis design.
H-axis or tumble-action machines repeatedly lift and drop clothes, instead of moving clothes around a central axis. H-axis washers also use sensor technology to closely control the incoming water temperature. To reduce water consumption, they spray clothes with repeated high-pressure rinses to remove soap residues rather than soaking them in a full tub of rinse water.
Click the "play" button to see how an H-axis washing machine works. (Note: The animation has no audio.)
In a study conducted by Oak Ridge national Laboratory (ORNL) in 1998 for U.S. Department of Energy, it was found that, on average, the h-axis washer used 62.2 percent of the water used by the v-axis washer, and this yielded total water savings of 37.8 percent. Moreover, the average h-axis washer consumed 42.4 percent of the energy used by a typical v-axis washer in the study, resulting in energy savings of 57.6 percent.
Features of the h-axis washer include:
Stricter new federal standards for clothes washers took effect in two stages. The first stage was in force as of January 2004. Then in 2007, the second stage further strengthened the standard. Three factors are used in determining the federal standards:
For more information about MEF circulation, please see the August 27, 1997 Federal Register entry regarding 10 CFR Part 430.
In addition:
Many new energy-efficient, water-conserving clothes washers have been introduced over the past few years. These resource-efficient washers are available in a variety of sizes and configurations, offering consumers a wide range of front-loading and top-loading styles in many different price ranges.
A clothes dryer dries wet clothes in a rotating drum through which hot air is circulated.
Clothes dryers can be of two types: electric and gas.
Dryers work by heating and aerating clothes. The efficiency of clothes dryer is measured by a term called the Energy Factor. It is similar to the miles per gallon for a car, but in this case the measure is pounds of clothing per kilowatt-hour of electricity.
The minimum Energy Factor rating for a standard capacity electric dryer is 3.01. For gas dryers, the minimum energy factor is 2.67. The rating for gas dryers is provided in kilowatt-hours though the primary source of fuel is natural gas.
Unlike most other types of appliances, energy consumption does not vary significantly among comparable models of clothes dryers. Clothes dryers are NOT required to display EnergyGuide labels.
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 percent of this energy is used, not to run the machine, but to heat the water for washing the dishes.
The dishwasher is the only device at home that requires a water heater temperature that is about 140°F. The units built recently have supplemental heaters in the dishwashers to bump up the temperature so that the main water heater temperature can be set at 120°F or less. Remember that each 10°F reduction in water heater temperature lowers the water heater energy cost by 3 percent to 5 percent.
A dishwasher is essentially an insulated water tight box. The dirty dishes are systematically arranged in the dishwasher. As shown below, hot water is sprayed on to the dishes as jets. Repeated jets of water emanating from a spray arm clean the dishes. Some models have two spray arms: one at the bottom of the dishwasher (lower spray arm) and one at the top (upper spray arm). The dirty water passes through a filter and re-circulates until the dishes are finished. Fresh water is then spayed during the rinse cycle to remove the soapy water. Then the dishes are dried with either electric heat or simply with air.
Press the “play” button to see how a dishwasher works. This is also described in the paragraph above. (Note: The animation has no audio.)
Dishwashers can be built-in or portable. Built-ins are mounted under a kitchen countertop usually next to a sink. Portables are on wheels with finished tops and sides. Most models can be converted into under-counter mounting. However, because of the additional connection hardware and finished sides, portables usually cost more than similar built-in models.
Some of the additional features that are offered are:
Energy Factor (EF) is the dishwasher energy performance metric. EF is expressed in cycles per kWh and is the reciprocal of the sum of the machine electrical energy per cycle, M, plus the water heating energy consumption per cycle, W.
Energy Factor (EF) = 1 / M + W
This equation may vary based on dishwasher features such as water-heating boosters or truncated cycles. The greater the EF, the more efficient the dishwasher is.
The EF is the energy performance metric of both the federal standard and the ENERGY STAR qualified dishwasher program. The federal EnergyGuide label on dishwashers shows the annual energy consumption and cost. These figures use the energy factor, average cycles per year, and the average cost of energy to make the energy and cost estimates. The EF may not appear on the EnergyGuide label.
Dishwasher manufacturers must self-test their equipment according to the new Department of Energy (DOE) test procedure defined in 10 CFR 430, Subpart B, Appendix C. This DOE test procedure was announced on August 29, 2003, and all models had to be tested using the new procedure by February 25, 2004.
This test procedure establishes a separate test for soil-sensing machines. Included in the final rule was a decision to add standby energy consumption to the annual energy and cost calculation, but not to the energy factor calculation. Also, the average cycles per year has been lowered from 264 cycles per year to 215 cycles per year. Energy Star dishwashers are at least 25 percent more energy efficient than minimum federal government standards.
The table below lists the standard and the ENERGY STAR approved dishwasher energy factors.
Product Type | Federal Standard Energy Factor | ENERGY STAR Energy Factor |
---|---|---|
Standard ( > 8 place settings + six serving pieces) | > 0.46 | > 0.58 |
Compact (< 8 place settings + six serving pieces) | > 0.62 | NA |
The current ENERGY STAR criteria for dishwashers became effective January 1, 2001. This criteria of at least 25 percent above the federal standard and applies only to models manufactured after January 1, 2001. The previous ENERGY STAR criterion was 13 percent above the federal standard.
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, but you may actually consume more energy operating them more frequently. The following tips help you to save even more:
The questions below are your chance to test and practice your understanding of the content covered in this lesson. In other words, you should be able to answer the following questions if you know the material that was just covered! If you have problems with any of the items, feel free to post your question on the unit message board so your classmates, and/or your instructor, can help you out!
You must complete a short quiz that covers the reading material in lesson 5. The Lesson 5 Quiz, can be found in the Lesson 5: Appliances module in Canvas. Please refer to the Calendar in Canvas for specific time frames and due dates.
Links
[1] https://www.energy.gov/eere/office-energy-efficiency-renewable-energy
[2] http://www.eere.energy.gov/
[3] https://www.consumer.ftc.gov/articles/0072-shopping-home-appliances-use-energyguide-label
[4] http://en.wikipedia.org/wiki/File:ThermodynamicPanelsInstalled.jpg
[5] https://www.e-education.psu.edu/egee102/sites/www.e-education.psu.edu.egee102/files/longdesc/Lesson_05/Life_cycle_analysis_LD.html
[6] http://www.energystar.gov
[7] https://upload.wikimedia.org/wikipedia/commons/f/f7/View_of_dishwasher_inside.jpg
[8] https://commons.wikimedia.org/wiki/User:Catfisheye
[9] https://creativecommons.org/licenses/by-sa/2.0
[10] http://www.aceee.org/consumerguide/topfurn.htm
[11] http://www.eere.energy.gov/consumerinfo/factsheets/ea3.html
[12] http://www.eere.energy.gov/consumerinfo/factsheets/ed3.html
[13] http://www.naima.org/pages/resources/library/pdf/BI403.PDF
[14] http://www.naima.org/pages/resources/library/pdf/BI409.PDF
[15] http://www.eere.energy.gov/consumerinfo/energy_savers/insulation.html