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A light-emitting diode, or LED, is the most efficient form of lighting available. Producing 100 lumens per watt, they can significantly reduce the amount of electricity that a family uses for lighting. Because they last about 25,000 hours, an LED bulb can be installed and left in place for years without needing replacement. LED bulbs were once extremely expensive, but today they are no more expensive than CFL or halogen-incandescent bulbs. Many schools and commercial buildings with large spaces to light, such as a gymnasium or warehouse, use metal halide lighting. These large bulbs use 350-400 watts each and require 10-20 minutes to reach their full brightness. Because they use so much power, many schools and businesses are choosing to change these lights for LED fixtures of equivalent brightness. Metal halide lights are generally not found in homes because they are so bright and get very hot.

ƒ Appliances and Other Plug Loads You may be wondering what a plug load is. Anything that has a cord, and plugs into an electrical outlet, is a plug load. In electricity, a “load” is any device that uses power. Light bulbs, motors, computers, and your video game system are all loads. Refrigerators and window air conditioners have compressors in them that use the principles of pressure and temperature to cool a space, whether it’s the interior of a freezer or a room. Washing machines and dishwashers have motors and pumps that run the appliances through their respective cycles. Blenders, food processors, hair dryers, and fans have motors that change the electricity into motion and spin the blades. And let us not forget the dozens and dozens of electronic devices that keep us connected to the outside world. Over 15 percent of a family’s electricity is used to power large appliances, small appliances, and electronic devices. As technology has improved, so has the efficiency of appliances, both large and small. For example, the way refrigerators function has not changed much in the last 50 years, but the efficiency of refrigerators has changed significantly. Today’s models keep food colder longer while using less energy. Some models are even Wi-Fi connected to let you know what’s inside when away from home. The Environmental Protection Agency created the ENERGY STAR® program to identify the appliances and devices that use less energy than others doing the same job. ENERGY STAR® rated devices are some of the top-rated machines in their class and will help keep energy bills low. However, all that efficiency comes with a price tag, as more efficient models are often more expensive. The energy savings will eventually offset the higher purchase price. However, a family desperate to replace a broken refrigerator may be shopping with one number in mind – price – and may be unable to afford a new, efficient model that keeps food fresh while using less electricity.

ELECTRICAL POWER SECTOR

As discussed earlier, most electricity is generated by natural gas, coal, uranium, and hydropower. All of these sources along with wind and geothermal energy use a turbine to change the linear motion of steam, flowing water, or wind into rotational motion for a generator. The generator in turn changes the rotational motion of the turbine into electrical energy that we use daily. Generating electricity uses more energy than any other use in the United States. Electricity generation carries with it a big carbon footprint, which is a way of describing how much an activity contributes to carbon dioxide emissions. The U.S. Department of Energy estimates that for every kilowatt-hour of electricity generated, 1.6 pounds of carbon dioxide are released into the atmosphere. The average family uses 914 kilowatt-hours of electricity every year.

ƒ Electricity Generation and Transmission Electricity is passed through a system of transformers and wires known as the grid. A transformer is a device that increases or decreases the voltage of the power leaving the power plant. Stepup transformers increase voltage, while step-down transformers decrease voltage. The process of generating electricity can be inefficient. A thermal power plant, fueled by natural gas, coal, uranium, or geothermal energy, changes only about 35 percent of the energy in those sources to electricity. The other 65 percent is lost to the surrounding environment as waste heat. As electricity is transferred through the grid to homes and businesses, friction in the lines carrying the energy results in more losses.

The Language of Electricity

Suppose you met someone from the 16th century. How would you define electricity? What exactly is going on when you flip a switch? Electricity is how we describe energized electrons passing their energy along a conductor to do work. But where did those electrons get their energy? And how do they transfer the energy to do work? Voltage is the way we describe an electron’s potential to do work. Technically, it’s the potential of a charged particle to cross the space between two charged plates. But it’s easier to think of voltage as the strength of the push behind electrons. High voltage, bigger push. Current is the term that tells us how many electrons are moving through a conductor. It is measured in Amperes, or just Amps. Current and voltage combine to describe power, or how much work is being done in a given time period. 100 Watts can be 100 Amps with 1 volt, or 10 Amps with 10 volts, or 1 Amp with 100 volts. Power = Voltage × Current.