Electricity is powered by converting other forms of energy, most commonly heat, moving water, wind, or sunlight, into electrical current. Nearly all electricity generation worldwide relies on a single physical principle discovered in the 1830s: moving a magnet inside a coil of wire causes electric current to flow through the wire. This process, called electromagnetic induction, is what happens inside the generators at virtually every power plant on Earth, whether that plant burns coal, splits atoms, or captures wind.
The differences between energy sources come down to what spins the generator. A moving fluid (steam, water, combustion gas, or air) pushes a series of blades mounted on a rotor shaft, and that spinning shaft turns the generator’s electromagnetic core to produce electricity. Understanding what creates that motion is the key to understanding what electricity is actually “powered by.”
Fossil Fuels: Gas, Coal, and Oil
Fossil fuels still produce the largest share of the world’s electricity. The basic idea is simple: burn fuel to create heat, use that heat to boil water into steam, and send the steam through a turbine connected to a generator. Natural gas plants work slightly differently. Fuel is injected into combustion chambers where it mixes with compressed air and burns at temperatures above 2,000°F. The resulting high-pressure gas expands directly through a turbine, spinning it to generate electricity.
A simple natural gas turbine converts only 20 to 35 percent of the fuel’s energy into electricity. The rest escapes as waste heat. Modern combined-cycle plants capture that waste heat to boil water and drive a second turbine, pushing efficiency as high as 60 percent. When the leftover heat is also piped to nearby buildings or industrial facilities, the overall energy use can approach 80 percent of what the fuel originally contained.
Coal plants work on the older steam-only model: burn coal in a furnace, boil water, send steam to a turbine. They’re generally less efficient and produce more carbon dioxide per unit of electricity, which is why coal’s share of the global power mix has been shrinking for over a decade.
Nuclear Power
Nuclear plants generate electricity the same way coal plants do, with one critical difference: the heat comes from splitting atoms instead of burning fuel. Inside a reactor, uranium fuel rods undergo a chain reaction that releases enormous amounts of heat. That heat boils water, and from there the process is identical: steam spins a turbine, the turbine turns a generator, and the generator produces electricity.
There are two main reactor designs. In a boiling water reactor, water flows directly past the fuel rods and turns to steam. In a pressurized water reactor, the water near the fuel is kept under such high pressure that it can’t boil. Instead, this superheated water passes through a separate steam generator, where it transfers its heat to a second water system that does boil. Either way, once the steam has passed through the turbine, it enters a condenser (a house-sized metal box with thousands of cooling pipes) where it turns back into liquid water and cycles through again.
Because no fuel is burned, nuclear plants produce no carbon dioxide during operation. A single uranium fuel pellet the size of a pencil eraser contains as much energy as a ton of coal, which is why nuclear plants can run for 18 to 24 months between refueling.
Solar Energy
Solar power reaches your outlet through two completely different technologies. The one you see on rooftops, photovoltaic (PV) panels, is the only major electricity source that skips the turbine-and-generator setup entirely. PV cells convert sunlight directly into electric current using semiconductor materials. When photons from sunlight knock electrons loose inside the cell, those electrons flow as direct current (DC). An inverter then converts that DC into the alternating current (AC) your home uses.
The second approach, concentrated solar power (CSP), works more like a traditional power plant. A field of mirrors reflects sunlight onto a central tower, concentrating enough thermal energy to heat a fluid and produce steam. That steam drives a turbine and generator just like in a fossil fuel plant. CSP is far less common than PV but has one advantage: it can store heat in molten salt and keep generating electricity after sunset.
Solar PV is the fastest-growing electricity source in the world by a wide margin. Between 2025 and 2030, global renewable power capacity is projected to increase by nearly 4,600 gigawatts, and solar PV alone accounts for almost 80 percent of that expansion, according to the International Energy Agency.
Wind Power
Wind turbines convert the kinetic energy of moving air into electricity. Wind pushes against large blades, causing them to rotate. That rotation spins a shaft connected to a generator inside the turbine’s housing (the box-shaped structure at the top of the tower). No fuel, no steam, no combustion. The wind itself is the moving fluid that does the work.
There’s a physical ceiling on how much energy any turbine can extract from the wind: about 59 percent, known as the Betz limit. Real-world turbines capture roughly 50 percent. The more practical measure is capacity factor, which compares a turbine’s actual output over time to its theoretical maximum. U.S. onshore wind turbines average a 38 percent capacity factor, meaning they produce about 38 percent of what they would if conditions were always ideal. Offshore turbines perform better because ocean winds blow stronger and more consistently. New offshore projects are expected to reach capacity factors around 60 percent by 2050.
Cumulative onshore wind installations are forecast to grow 45 percent between 2025 and 2030 compared to the previous five years, while offshore wind capacity is expected to more than double over the same period.
Hydroelectric Power
Hydropower uses the gravitational energy of falling water. In a typical dam, water held in a reservoir flows downward through a large pipe called a penstock. At the bottom, the rushing water hits a turbine propeller and spins it. A shaft from the turbine connects to a generator above, which produces electricity. The higher the dam and the more water flowing through it, the more power it generates.
Hydropower is one of the oldest and most reliable sources of electricity. Unlike wind and solar, it can be ramped up or down in seconds by controlling how much water passes through the turbines, making it valuable for balancing grid demand. More than 154 gigawatts of new hydropower capacity is expected to come online globally between 2025 and 2030.
Geothermal Energy
Geothermal plants tap heat stored beneath Earth’s surface. In volcanic or tectonically active regions, underground reservoirs of hot water or steam can be accessed by drilling. The simplest plants pipe that steam directly to a turbine. Where underground temperatures are lower, binary-cycle plants pump the hot water past a second liquid with a much lower boiling point. That second liquid vaporizes and drives the turbine instead. Either way, the end result is the same: a spinning generator producing electricity from Earth’s internal heat, available 24 hours a day regardless of weather.
How Electricity Reaches You
Once a generator produces electricity, it travels through a network called the grid. Power plants produce electricity at relatively low voltages, which transformers then step up to extremely high voltages for long-distance transmission. High voltage reduces energy lost as heat in the wires. Near your neighborhood, another transformer steps the voltage back down to the 120 or 240 volts your home uses.
Because electricity must be used the instant it’s generated (the grid has almost no built-in storage), grid operators constantly match supply to demand in real time. This is where battery storage is becoming increasingly important. Utility-scale batteries with four- to eight-hour capacity store excess electricity, often from solar panels generating at midday, and release it during evening peak hours when solar output drops. More than 60 percent of new utility-scale battery capacity is being paired with solar plants for exactly this purpose. Shorter-duration batteries, discharging for seconds to minutes, help stabilize the grid by smoothing out sudden fluctuations in supply or demand.
The Shifting Power Mix
The global electricity supply is in the middle of a significant transition. Fossil fuels still generate the majority of the world’s power, but renewables are growing at an unprecedented rate. The IEA projects that renewable capacity additions between 2025 and 2030 will double those of the previous five years. Solar PV accounts for over half of the increase in renewable electricity generation, followed by wind at about 30 percent.
What powers your electricity depends on where you live. Some regions rely heavily on hydropower, others on natural gas, and a growing number on wind and solar. But the underlying principle is remarkably consistent across almost every source: something spins a generator, and electromagnetic induction turns that motion into the current flowing through your walls.