Solar energy is made by converting sunlight into electricity, either by using semiconductor materials that generate electric current when light hits them or by using mirrors to concentrate sunlight into heat that drives a turbine. The first method, called photovoltaic (PV) technology, powers the vast majority of rooftop and utility-scale solar installations. The second, concentrated solar power (CSP), is used in large desert plants. Both start with the same raw ingredient: photons streaming from the sun.
How Solar Panels Turn Light Into Electricity
A solar panel is made of silicon, a semiconductor material that sits in an interesting middle ground: it doesn’t conduct electricity on its own, but it becomes conductive when photons from sunlight hit its surface with enough energy. That interaction is the photovoltaic effect, and it works in three steps.
First, the silicon absorbs incoming photons. When a photon carries enough energy, it knocks an electron loose from its fixed position in the silicon crystal, bumping it into a higher energy state where it can move freely. This creates a charge carrier: a free electron and the “hole” it left behind. Second, the structure of the solar cell separates these positive and negative charges. Silicon cells are built with two layers, one with a slight positive charge and one with a slight negative charge, creating an internal electric field that pushes electrons in one direction and holes in the other. Third, metal contacts on the top and bottom of the cell collect those flowing electrons and channel them into a circuit. That flow of electrons is direct current (DC) electricity.
Each individual solar cell produces a small amount of power. A typical residential panel wires together 60 to 72 cells to produce a usable voltage, and multiple panels are wired together into an array to meet a home’s or building’s energy needs.
Concentrated Solar Power: Heat Instead of Electrons
Concentrated solar power takes a completely different approach. Instead of converting photons directly into electricity, CSP plants use large arrays of mirrors to reflect and focus sunlight onto a receiver, heating a fluid to extremely high temperatures. That thermal energy then spins a turbine to generate electricity, much like a coal or natural gas plant does, just without burning fuel.
There are three main CSP designs. Power tower systems arrange thousands of flat, sun-tracking mirrors around a central tower, focusing light onto a receiver at the top. Linear systems use long, curved mirrors to concentrate sunlight onto a tube running along the focal line. Dish systems use a parabolic dish of mirrors to direct sunlight onto a small engine at the center. All three rely on the same principle: concentrating diffuse sunlight into intense heat, then converting that heat into mechanical and then electrical energy.
CSP plants are typically built in deserts and arid regions with strong, consistent direct sunlight. They’re far less common than photovoltaic installations but have one advantage: they can store heat in molten salt or similar materials, allowing them to generate electricity for hours after the sun goes down.
From DC to Usable Power
Solar panels produce direct current, where electricity flows in one constant direction. Your home, your appliances, and the electrical grid all run on alternating current (AC), where the voltage switches direction many times per second. Bridging that gap is the job of an inverter.
An inverter works by switching the direction of the DC input back and forth very rapidly, turning a steady one-way flow into an oscillating output. Filters and additional electronics smooth that output into a clean, repeating wave that matches the grid’s frequency. Without the inverter, the electricity your panels produce would be incompatible with virtually everything in your home.
In most residential systems, either a single central inverter handles the output of all panels, or small microinverters are attached to each panel individually. Microinverters let each panel operate independently, which helps when some panels are shaded and others aren’t.
Storing Solar Energy in Batteries
Solar panels only generate electricity when the sun is shining. If you want to use solar power at night or during cloudy stretches, you need a battery. Home battery systems store excess daytime electricity as chemical energy, then release it when your panels aren’t producing.
Between the panels and the battery sits a charge controller, a device that regulates voltage and current to protect the battery from overcharging. Solar panels can output anywhere from 16 to 20 volts depending on conditions, but a battery might need anywhere from about 10.5 to 14.6 volts depending on how full it is and what type it is. The charge controller adjusts that voltage in real time, feeding the battery only what it can safely accept. Without one, you’d risk damaging or significantly shortening the life of your battery.
Sending Power Back to the Grid
Most home solar systems are connected to the utility grid, and during the day they often produce more electricity than the household uses. Net metering is the billing mechanism that handles this surplus. When your panels generate more than you need, the excess flows back into the grid, and your electric meter effectively runs backward, giving you a credit.
At night, or whenever your usage exceeds what your panels produce, you draw power from the grid as usual. At the end of the billing cycle, you’re charged only for your “net” energy use: what you consumed minus what you exported. For many solar households, this means dramatically lower electric bills and, in some months, a credit that rolls forward.
How Much Sunlight Actually Becomes Electricity
Not every photon that hits a solar panel gets turned into electricity. Some photons carry too little energy to knock electrons loose. Others carry more than enough, and the excess becomes waste heat. The panel’s surface reflects some light, and internal resistance eats into the output further.
Most home solar panels today have efficiency ratings between 21% and 22%, with top brands reaching 23% or higher. Nearly every residential installation uses monocrystalline silicon panels because they deliver the highest efficiency of any widely available technology. Polycrystalline panels are slightly cheaper but convert less sunlight, making monocrystalline the better value for most rooftops where space is limited.
In the lab, researchers have pushed well beyond those numbers. A tandem cell that layers a newer material called perovskite on top of traditional silicon reached a certified efficiency of 34.85% in 2025, set by the Chinese manufacturer LONGi. That kind of cell captures a broader range of the solar spectrum by using two different materials tuned to different wavelengths. It will take years for tandem technology to reach mass production, but it signals that the ceiling for solar efficiency is still rising.
What Affects Solar Output
Geography matters enormously. Solar panels perform best under direct sunlight, and areas closer to the equator or at higher elevations receive more intense solar radiation throughout the year. Cloud cover, humidity, and even the water vapor in the atmosphere absorb portions of the sun’s energy before it reaches the ground, particularly in the near-infrared part of the spectrum.
Panel orientation and tilt also play a role. In the Northern Hemisphere, south-facing panels at a tilt angle roughly equal to your latitude will capture the most annual sunlight. Shading from trees, chimneys, or neighboring buildings can cut output significantly, since even partial shade on one section of a panel can reduce the performance of the whole string if the system uses a central inverter. Temperature is a less obvious factor: solar cells actually become slightly less efficient as they heat up, so a cool, sunny day produces more electricity than a blazing hot one at the same light level.