Here is how the story begins. People use electricity to light their homes. But before electricity became widely available, candles, whale oil lamps and kerosene lamps provided light, iceboxes kept food cold, and wood or coal stoves provided heat. Edison was not the inventor of the light bulb, but rather the inventor of the first effective and commercially viable one. The earliest bulbs failed because the metal filament got too hot and melted. Edison found that a loop of carbonized thread did not melt, giving long life. He first patented his carbon-filament lamp on 1 November 1879, after his laboratory got a glowing carbonized thread that lasted more than fourteen hours. Thomas Edison invented a long-lasting light bulb around 1879.

Electricity is made at power plants, and Pearl Street was one. In 1882, Edison’s Pearl Street Station in New York City began sending out electricity. It was designed to run up to 1,400 lamps continuously and served an area of about one square mile. For it, Edison’s team built six huge dynamos nicknamed “Jumbo.” Each weighed about 27 tons and put out 100 kilowatts. A kilowatt is 1,000 watts. A 40-watt light bulb used for five hours uses 200 watt-hours, or 0.2 kilowatt-hours, of electrical energy. Edison’s direct current (DC) was not easily converted to higher or lower voltages. Power lines carry electricity over long distances, so that limit was a big one.

Why did that matter? Electricity is called an energy carrier, because it can be converted to other forms of energy such as mechanical energy or heat. Higher-voltage electricity is more efficient and less expensive for long-distance travel, and lower-voltage electricity is safer to use in homes and businesses. A transformer raises or lowers the voltage of electricity. A transformer steps up the voltage before transmission, so lower currents can carry the same energy and less is lost. A transformer at a substation lowers the voltage again. From a substation, smaller, lower-voltage lines bring electricity to neighborhoods and homes. Electric current is the rate at which charge flows. In metal wires, current is carried by electrons. The ampere (A) is the base unit of electric current.

Here is how the other side of the story went. Alternating current (AC) reverses direction 60 times a second in the U.S. It can be converted with a transformer, and Edison’s DC could not be changed so easily. AC could carry high voltages long distances and then be transformed into lower voltages for customers. George Westinghouse and Nikola Tesla won electric companies’ support for alternating current. Westinghouse’s win over direct current was symbolized by his lighting of the 1893 Columbian Exposition in Chicago. It was also symbolized by the rights he secured to develop Niagara Falls through AC generators. On Nov. 16, 1896, Buffalo was lit up by the alternating current from Niagara Falls. Most of the electricity we use today is AC.

Both kinds of current go back to one idea, so let us look at it. It is Faraday’s idea. Moving a magnet through a coil of wire can make electricity flow in the wire. Electromagnetic induction was the most important of Faraday’s discoveries. Without it, power generation and power transmission would be impossible. He found it in August 1831. Passing a magnet back and forth through a coil made the needle of a galvanometer register a current. A basic electromagnetic generator has insulated wire coils forming a stationary stator around a rotor. Turning the rotor makes an electric current flow in each section of the wire coil. Combined-cycle systems use the combustion gases from one turbine to generate more electricity in another turbine.

How much electricity is made today? In 2025, net generation of electricity from utility-scale generators in the United States was about 4,429 billion kilowatt-hours, which is about 4.43 trillion kWh. That is the figure as of November 2026. In 2025, about 58% of U.S. utility-scale electricity came from fossil fuels, about 18% from nuclear energy, about 19% from nonhydroelectric renewables, and about 24% from renewable sources. That is the picture as of November 2026, too. Some power is lost on the way to us. U.S. electricity transmission and distribution losses averaged about 5% of the electricity transmitted and distributed in 2018 through 2022, as of November 2026. Peak-load service helps meet electricity demand when it is highest, such as in the late afternoon when air conditioning use rises in hot weather. For the grid to stay stable, the amount of electricity supplied must match the electricity demanded. If they fall out of balance, local or even widespread blackouts can happen.

Words to know

• filament: thin glowing wire
• dynamos: big generators
• transformer: voltage changer
• alternating: reversing
• ampere: current unit