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Energy conservation is the practice of decreasing the quantity of energy used while achieving a similar outcome of end use. This practice may result in increase of financial capital, environmental value, personal security, and comfort. Individuals and organizations that are direct consumers of energy may want to conserve energy in order to reduce energy costs and promote economic, political and environmental sustainability. Industrial and commercial users may want to increase efficiency and thus maximize profit.
On a larger scale, energy conservation is an important element of energy policy. In general, energy conservation reduces the energy consumption and energy demand per capita, and thus offsets the growth in energy supply needed to keep up with population growth. This reduces the rise in energy costs, and can reduce the need for new power plants, and energy imports. The reduced energy demand can provide more flexibility in choosing the most preferred methods of energy production.
By reducing emissions, energy conservation is an important part of lessening climate change. Energy conservation facilitates the replacement of non-renewable resources with renewable energy. Energy conservation is often the most economical solution to energy shortages, and is a more environmentally benign alternative to increased energy production.
 Energy Efficiency trends in the United States
The U.S. is currently the biggest consumer of energy in the world, although at current levels of growth, it is possible that in the future China could become the leading energy consumer. The U.S. Department of Energy categorizes national energy use in four broad sectors: transportation, residential, commercial, and industrial.
Energy usage in the transportation and residential sectors (about half of U.S. energy consumption) is largely controlled by individual domestic consumers. Commercial and industrial energy expenditures are determined by businesses entities and other facility managers. National energy policy has a significant effect on energy usage across all four sectors.
 Transportation sector
The transportation sector includes all vehicles used for personal or freight transportation. Of the energy used in this sector, approximately 65% is consumed by gasoline-powered vehicles, primarily personally owned. Diesel-powered transport (trains, merchant ships, heavy trucks, etc.) consumes about 20%, and air traffic consumes most of the remaining 15%. The oil supply crises of the 1970s spurred the creation, in 1975, of the federal Corporate Average Fuel Economy (CAFE) program, which required auto manufacturers to meet progressively higher fleet fuel economy targets. The next decade saw dramatic improvements in fuel economy, mostly the result of reductions in vehicle size and weight. These gains eroded somewhat after 1990 due to the growing popularity of sport utility vehicles, pickup trucks and minivans, which fall under the more lenient "light truck" CAFE standard.
In addition to the CAFE program, the U.S. government has tried to encourage better vehicle efficiency through tax policy. Since 2002, taxpayers have been eligible for income tax credits for gas/electric hybrid vehicles. A "gas-guzzler" tax has been assessed on manufacturers since 1978 for cars with exceptionally poor fuel economy. While this tax remains in effect, it currently generates very little revenue as overall fuel economy has improved.
Another focus in gasoline conservation is reducing the number of miles driven. An estimated 40% of American automobile use is associated with daily commuting. Many urban areas offer subsidized public transportation to reduce commuting traffic, and encourage carpooling by providing designated high-occupancy vehicle lanes and lower tolls for cars with multiple riders.
In recent years telecommuting has also become a viable alternative to commuting for some jobs, but as of 2003 only 3.5% of workers were telecommuters. Ironically, hundreds of thousands of American and European workers have been replaced by workers in Asia who telecommute from thousands of miles away.
A vehicle's gas mileage normally decreases rapidly at speeds above 55 miles per hour. A car or truck moving at 55 miles an hour can get about 15 percent better fuel economy than the same car going 65 mph. According to the U.S. Department of Energy (DOE), as a rule of thumb, each 5 mph you drive over 60 mph is similar to paying an additional $0.21 per gallon for gas (at $3.00 per gallon). 
An idea has been proposed in this paper, in which the amount of emission a vehicle user is generating can be quantified and visualized in terms of a geographical area large enough to absorb all that pollution.
 Residential sector
The residential sector refers to all private residences, including single-family homes, apartments, manufactured homes and dormitories. Energy use in this sector varies significantly across the country, due to regional climate differences and different regulation. On average, about half of the energy used in the U.S. homes is expended on space conditioning (i.e. heating and cooling).
The efficiency of furnaces and air conditioners has increased steadily since the energy crises of the 1970s. The 1987 National Appliance Energy Conservation Act authorized the Department of Energy to set minimum efficiency standards for space conditioning equipment and other appliances each year, based on what is "technologically feasible and economically justified". Beyond these minimum standards, the Environmental Protection Agency awards the Energy Star designation to appliances that exceed industry efficiency averages by an EPA-specified percentage.
Despite technological improvements, many American lifestyle changes have put higher demands on heating and cooling resources. The average size of homes built in the United States has increased significantly, from 1500 ft² in 1970 to 2300 ft² in 2005. The single-person household has become more common, as has central air conditioning: 23% of households had central air conditioning in 1978, that figure rose to 55% by 2001.
As a cheaper alternative to the purchase of a new furnace or air conditioner, most public utilities encourage smaller changes the consumer can make to lessen space conditioning usage. Weatherization is frequently subsidized by utilities or state/federal tax credits, as are programmable thermostats. Consumers have also been urged to adopt a wider indoor temperature range (e.g. 65 °F in the winter, 80 °F in the summer).
 Home energy consumption averages
From the US Dept. of Energy, "Buildings Energy Data Book"
- space conditioning, 44%
- water heating, 13%
- lighting, 12%
- refrigeration, 8%
- home electronics, 6%
- laundry appliances, 5%
- kitchen appliances, 4%
- other uses, 8%
Energy usage in some homes may vary widely from these averages. For example, milder regions such as the southern U.S. and Pacific coast of the USA need far less energy for space conditioning than New York City or Chicago. In milder climates, lighting energy may easily consume up to 40% of total energy. Certain appliances such as a waterbed, hot tub, or pre-1990 refrigerator use significant amounts of electricity. In most residences no single appliance dominates, and any conservation efforts must be directed to numerous areas in order to achieve substantial energy savings. However, Ground Source Heat Pump systems are the more energy efficient, environmentally clean, and cost-effective space conditioning systems available (Environmental Protection Agency), and can achieve reductions in energy consumptions of up to 70%.
 Best building practices
Current best practices in building design and construction result in homes that are profoundly more energy conserving than average new homes. See Passive house, Superinsulation, Self-sufficient homes, Earthship, Straw-bale construction.
 Commercial sector
Energy in this sector has the same basic end uses as the residential sector, in slightly different proportions. Space conditioning is again the single biggest consumption area, but it represents only about 30% of the energy use of commercial buildings. Lighting, at 25%, plays a much larger role than it does in the residential sector. Lighting is also generally the most wasteful component of commercial use. A number of case studies indicate that more efficient lighting and elimination of over-illumination can reduce lighting energy by approximately fifty percent in many commercial buildings.
Commercial buildings can greatly increase energy efficiency by thoughtful design, with today's building stock being very poor examples of the potential of systematic (not expensive) energy efficient design (Steffy, 1997). Commercial buildings often have professional management, allowing centralized control and coordination of energy conservation efforts. As a result, fluorescent lighting (about four times as efficient as incandescent) is the standard for most commercial space, although it may produce certain adverse health effects. Potential health concerns can be mitigated by using newer fixtures with electronic ballasts rather than older magenetic ballasts. As most buildings have consistent hours of operation, programmed thermostats and lighting controls are common. However, too many companies believe that merely having a computer controlled Building automation system guarantees energy efficiency. As an example one large company in Northern California boasted that it was confident its state of the art system had optimized space heating. A more careful analysis by Lumina Technologies showed the system had been given programming instructions to maintain constant 24 hour temperatures in the entire building complex. This instruction caused the injection of nighttime heat into vacant buildings when the daytime summer temperatures would often exceed 90 degrees Fahrenheit. This mis-programming was costing the company over $130,000 per year in wasted energy (Lumina Technologies, 1997). Many corporations and governments also require the Energy Star rating for any new equipment purchased for their buildings.
Solar heat loading through standard window designs usually leads to high demand for air conditioning in summer months. An example of building design overcoming this excessive heat loading is the Dakin Building in Brisbane, California, where fenestration was designed to achieve an angle with respect to sun incidence to allow maximum reflection of solar heat; this design also assisted in reducing interior over-illumination to enhance worker efficiency and comfort.
 Industrial sector
Increasing costs have forced energy-intensive industries to make substantial efficiency improvements in the past 30 years. For example, the energy used to produce steel and paper products has been cut 40% in that time frame, while petroleum/aluminum refining and cement production have reduced their usage by about 25%. These reductions are largely the result of recycling waste material and the use of cogeneration equipment for electricity and heating.
The energy required for delivery and treatment of fresh water often constitutes a significant percentage of a region's electricity and natural gas usage (an estimated 20% of California's total energy use is water-related. In light of this, some local governments have worked toward a more integrated approach to energy and water conservation efforts.
Unlike the other sectors, total energy use in the industrial sector has declined in the last decade. While this is partly due to conservation efforts, it's also a reflection of the growing trend for U.S. companies to move manufacturing operations offshore.
 Barriers to Conservation
In the US, it is suggested that the unavoidable customer charges in the electrical billing system are a barrier to electrical conservation and green house gas mitigation. The customer charge is fixed and is independent of the actual electricity consumption used. In trying to maximize their benefit from the unavoidable fixed customer charge, smaller electricity users are inclined to conserve less. The paper referenced explains the policy requirements and the change in the electrical rate required, along with its impacts. The results indicate that removing the fixed charges and increasing the electrical rate can be economical for the US, the electrical companies and the households and environmentally beneficial. The increased rate penalizes smaller users less and encourages smaller and larger users alike to conserve responsibly.
 Energy conservation in the United Kingdom
- main article: Energy conservation in the United Kingdom
Energy conservation in the United Kingdom has been receiving increased attention over recent years. Key factors behind this are the Government's commitment to reducing carbon emissions, the projected 'energy gap' in UK electricity generation, and the increasing reliance on imports to meet national energy needs. Domestic housing and road transport are currently the two biggest problem areas.
 Issues with energy conservation
Critics and advocates of some forms of energy conservation make the following arguments:
It may be difficult for home owners or small business to justify investment in some energy saving measures. Condensing boilers are very much more efficient than older types. Energy savings are achieved by venting less heat externally and heating water for showers etc, as it is used. Refrigeration is also a major factor of energy consumption, electronic Energy saving modules (ESM) can be added to existing HVAC and refrigeration systems at little cost to conserve electricity.
For transportation the same financial payback versus energy savings argument can be made. For example, new hybrid vehicles have a better miles per gallon rating than an equivalent conventional vehicle, but they have a higher initial cost due to the greater costs of manufacturing the vehicle. The higher costs of maintenance, insurance, and depreciation can outweigh the savings on fuel and tax credits (depending on the particular vehicle, and extent of the tax credit). The hybrid car may give 45 mpg, saving the average driver 278 gallons of fuel per year. The hybrid engine cost $3000 extra, so with gasoline at $2.50 per gallon, it pays for itself in 4.3 years, and saves over 1000 gallons of gasoline from being used. The resale value of a fuel-efficient vehicle may be higher than a conventional gas-powered vehicle.
Some retailers argue that bright lighting stimulates purchasing. Health studies have demonstrated that headache, stress (medicine), blood pressure, fatigue and worker error all generally increase with the common over-illumination present in many workplace and retail settings (Davis, 2001), (Bain, 1997). It has been shown that natural daylighting increases productivity levels of workers, while reducing energy consumption. Consumers are also motivated by a number of factors, and corporate stewardship may provide an incentive for shoppers to visit stores who conserve energy. Lower overhead costs may allow retailers to lower prices, stimulating consumption.
 See also
- Energy efficiency
- Energy Saving Modules
- Fuel economy
- Fuel efficiency
- Light pollution
- One Watt Initiative
- Thermal efficiency
- Renewable energy
- Bain, A., “The Hindenburg Disaster: A Compelling Theory of Probable Cause and Effect,” Procs. NatL Hydr. Assn. 8th Ann. Hydrogen Meeting, Alexandria, Va., March 11-13, pp 125-128 (1997}
- Gary Steffy, Architectural Lighting Design, John Wiley and Sons (2001) ISBN 0-471-38638-3
- Lumina Technologies, Analysis of energy consumption in a San Francisco Bay Area research office complex, for (confidential) owner, Santa Rosa, Ca. May 17, 1996
- ↑ J. M. Pearce and Paul J. Harris, "Reducing greenhouse gas emissions by inducing energy conservation and distributed generation from elimination of electric utility customer charges", Energy Policy, 35, pp. 6514-6525, 2007.
- ↑ Lumina Technologies Inc., Santa Rosa, Ca., Survey of 156 California commercial buildings energy use, August, 1996
- Choosing Energy Efficient Windows
- Energy conservation tips for apartments
- Energy Efficiency: First Things First
- Energy Saving Resources for the Home
- Dividing heating bill by ten to build for tomorrow(translated from French)
U.S. energy statistics:
- U.S. Energy Information Administration
- Buildings Energy Data - commercial/residential building consumption patterns
International collaborative research:
Energy conservation assistance for commercial and industrial businesses:
UNEP- Energy Branch: