How many storms are there at one time? As of November 2026, there can be as many as 2,000 thunderstorms occurring across the globe at any given moment. Lightning is a kind of electricity. It happens when electric charge builds up in a storm cloud and then jumps to the ground. NASA satellite research indicates that thunderstorms produce lightning flashes about 40 times a second worldwide, down from the 100 a second estimated in 1925. Benjamin Franklin did not discover electricity. Electrical forces had been recognized for more than a thousand years, and his experiment showed the connection between lightning and electricity. The word “electricity” comes from “elektron,” the Greek word for amber. Static electricity is another place where electrons are on the move. Rubbing can move electrons from one thing to another, and that is how static electricity starts. It can make your hair stand on end. Electric charges that are alike push each other apart.

Now think very small. Atoms are made of protons, neutrons and electrons. If an atom’s nucleus were the size of a tennis ball, the whole atom would be about the size of a large sports stadium, about 1,450 feet across, and atoms are mostly empty space. The outer electrons in an atom have a weaker pull toward the protons and can move from one atom to another. These shifting electrons are what we call electricity. Electric current is the rate at which charge flows. In metal wires, current is carried by electrons. Metals let electricity flow through them easily. Glass, rubber, wood and plastic do not, and electricity only flows when it has a complete path, called a circuit. Conventional current is defined as the direction positive charge would flow. This goes back to Benjamin Franklin, who named the charge that electrons carry negative before they were known to carry current.

Let us see how electricity is measured, one unit at a time, and a light bulb is a good place to start, since people use electricity to light their homes. Electricity has its own units, and each unit measures something different. The ampere (A) is the base unit of electric current. 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. Transmission power lines typically have high voltages, up to 750,000 volts, but relatively low currents, up to 1000 amperes. A transformer steps up the voltage before transmission, so lower currents can carry the same energy and less is lost. 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.

Before electricity became widely available, candles, whale oil lamps and kerosene lamps provided light. Edison was not the inventor of the light bulb, but rather the inventor of the first effective and commercially viable one. 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. 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. At the beginning of the 20th century, more than 4,000 isolated electric utilities operated in the United States. Connecting utilities’ transmission systems also reduced the extra generating capacity each utility had to have available to ensure reliable service during peak demand.

Electricity is made at power plants, and power lines carry it over long distances. Let us count what is made. The electricity we use is a secondary energy source, because it is made by converting primary sources like coal, natural gas, nuclear, solar and wind energy. Primary energy sources are renewable or nonrenewable, but the electricity we use is neither renewable nor nonrenewable. In 2025, net generation of electricity from utility-scale generators in the United States was about 4,429 billion kilowatt-hours, about 4.43 trillion kWh. 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. These figures are as of November 2026. U.S. electricity transmission and distribution losses averaged about 5% of the electricity transmitted and distributed in 2018 through 2022, as of November 2026.

Let us end with what keeps the whole system working, and with some of the limits it has. 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. Power lines carry electricity over long distances. From a substation, smaller, lower-voltage lines bring electricity to neighborhoods and homes. If you see a power line on the ground, stay away from it and tell a grown-up right away. Wind and solar power plants generate electricity only when wind and solar energy resources are available. The smart grid combines digital technology and advanced tools with the traditional electrical system, so utilities and customers can send and receive information to and from the grid. Energy storage systems use electricity to charge, and the amount of electricity they can supply is less than the amount they use for charging.

Words to know

• ampere: current unit
• kilowatt: 1,000 watts
• nucleus: atom's center
• renewable: never used up
• transmission: long-distance carrying