Energy Efficiency

Energy efficiency or efficient energy use refers to technological improvements or usage modifications that allow the same amount of service at a lower energy input. One example is the replacement of incandescent light bulbs with fluorescent light bulbs -- fluorescent bulbs produce the same amount of light but require less energy. Another example would be insulating a building so that less energy is required for heating and cooling.  Along with increased renewable energy use, energy efficiency is an important means of moving away from carbon-intensive energy consumption patterns.  The average American household consumes about 10,000 kwh (kilowatt-hours) of electricity every year. Each kwh used equals two pounds of carbon dioxide released into the atmosphere.  Increased use of energy-efficient practices could reduce global energy consumption by a third.  Because of this, energy efficiency is an important component of any solution to global warming.  Energy efficiency is primarily achieved through the use of efficient technology or processes rather than by changes in individual behavior, or energy conservation .

Focusing on energy efficiency can help economic growth without necessarily increasing energy consumption. For example, in the mid-1970s, California began implementing energy-efficiency measures including building code and appliance standards with strict efficiency requirements. During the following years, California's energy consumption has remained approximately flat on a per capita basis while national U.S. consumption doubled. Still, efficiency often has taken a secondary position to new power generation as a solution to global warming in creating national energy policy. Some companies also have been reluctant to engage in efficiency measures, despite the often favorable returns on investments that can result. The Rocky Mountain Institute points out that in industrial settings, "there are abundant opportunities to save 70% to 90% of the energy and cost for lighting, fan, and pump systems; 50% for electric motors; and 60% in areas such as heating, cooling, office equipment, and appliances." In general, up to 75% of the electricity used in the U.S. today could be saved with efficiency measures that cost less than the electricity itself.

Energy efficient appliances

Modern appliances, including refrigerators, freezers, ovens, stoves, dishwashers, and clothes washers and dryers, use significantly less energy than older models. Current energy efficient refrigerators, for example, use 40 percent less energy than conventional models did in 2001. Power management systems also reduce energy usage by idle appliances by turning them off or putting them into a low-energy mode after a certain time.

Energy efficient building design

Green buildings draw upon energy efficient techniques for heating, cooling, and lighting improvements and the use of energy-saving appliances and equipment.

Energy efficiency for industry

In industry, when electricity is generated, the heat which is produced as a by-product can be captured and used for process steam, heating or other industrial purposes. Conventional electricity generation is about 30 percent efficient, whereas combined heat and power (also called cogeneration) converts up to 90 percent of the fuel into usable energy.

Other technologies, including those relating to steam and motors, can be used to make facilities more efficient.  Over 45 percent of the fuel used by US manufacturers is burnt to make steam. The typical industrial facility can reduce this energy usage 20 percent by insulating steam and condensate return lines, stopping steam leakage, and maintaining steam traps.  Electric motors usually run on a constant flow of energy, but an adjustable speed drive can vary the motor’s energy output to match the load. This achieves energy savings ranging from 3 to 60 percent, depending on how the motor is used.  Many other examples show how energy efficiency is applicable to heavy industry.

Energy efficient vehicles

Improving aerodynamics to minimize drag  and reducing vehicle weight can increase vehicle fuel efficiency.  Decreased friction tires help save gasoline. Fuel economy can be improved over three percent by keeping tires inflated to the correct pressure. Replacing a clogged air filter should improve a car's fuel consumption by as much as 10 percent

Fuel efficient vehicles may reach twice the fuel efficiency of the average automobile. Cutting-edge designs have achieved a fuel efficiency as high as 84 mpg (2.8 L/100 km), four times the current conventional automotive average.  Hybrids and electric cars represent a growing market that is energy-efficient and increasingly practical.

Rebound effect

If the demand for energy services remains constant, improving energy efficiency will reduce energy consumption and carbon emissions. However, many efficiency improvements do not reduce energy consumption by the amount predicted by simple models because they make energy services cheaper, increasing demand, and therefore consumption rises. For example, since fuel efficient vehicles make travel cheaper, consumers may choose to drive further and/or faster, thereby offsetting some of the potential energy savings. This is an example of the direct rebound effect.  Estimates of the size of the rebound effect range from roughly 5% to 40%. Rebound effects are smaller in mature markets where demand is saturated. The rebound effect is likely to be less than 30% at the household level and may be closer to 10% for transport. A rebound effect of 30% implies that improvements in energy efficiency should achieve 70% of the reduction in energy consumption projected using engineering models.

Energy conservation

Energy conservation emphasizes productive behavioral changes that cut down on unnecessary energy consumption.  Examples of conservation without efficiency improvements would be keeping the heat lower, driving less frequently, or working in a less brightly lit room. As with other definitions, the boundary between energy efficiency and energy conservation can be fuzzy, but both are important in environmental and economic terms.