Solar energy is simply radiant heat and light from the sun. According to the U.S. Energy Information Administration (EIA), people have used the sun’s rays for thousands of years for warmth and for drying food, but today we use technologies to capture solar energy and convert it into electricity. This process powers everything from tiny calculators to entire neighborhoods, and understanding it does not require an engineering degree.
What is solar energy?
The EIA explains that the sun is the original source for nearly all the energy we use on Earth. The sun constantly sends out radiant energy in the form of electromagnetic radiation, which the U.S. Department of Energy (DOE) describes as including both heat and light. Solar technologies capture this radiation and turn it into useful energy forms. While some systems use mirrors to concentrate sunlight for heat, the most common way beginners encounter solar energy is through photovoltaics, or PV, which converts sunlight directly into electricity.
If you are new to the topic, you might want to bookmark our Solar for Beginners hub for clear, plain-English explanations.
How a solar cell makes electricity
A photovoltaic cell, commonly called a solar cell, is a nonmechanical device that turns sunlight directly into electricity, according to the EIA. The DOE describes the process simply: when the sun shines onto a solar panel, energy from the sunlight is absorbed by the PV cells. This energy creates electrical charges that move in response to an internal electrical field in the cell, causing electricity to flow.
The EIA’s photovoltaics guide breaks this down further. Sunlight is composed of photons, or particles of solar energy. A PV cell is made of a semiconductor material. When photons strike the cell, only the absorbed photons provide energy to generate electricity. That energy dislodges electrons from the material’s atoms. Special manufacturing treatment makes the front surface of the cell more receptive to free electrons, so the electrons naturally migrate there. This movement creates an electrical charge imbalance between the front and back of the cell, creating a voltage potential similar to the terminals of a battery. When conductors on the cell are connected to an external load, such as a battery, electricity flows through the circuit.
This basic science is the foundation for every solar setup. You can explore it further in our article on How Solar Works.
From cells to panels to arrays
The EIA notes that a single PV cell is small and only produces 1 or 2 watts of power, which is just enough for calculators or wristwatches. To get useful amounts of electricity, manufacturers electrically connect multiple cells into a packaged, weather-tight unit called a PV panel, or module. Panels can then be connected in groups to form a PV array. An array can be as small as two panels or consist of hundreds of panels, and the total number of panels determines how much electricity the array can generate.
DC vs AC: Why you need an inverter
The electricity that comes out of a solar panel is direct current (DC) electricity. The EIA explains that DC power can charge batteries directly, which is useful for devices that run on DC. However, nearly all electricity supplied in transmission and distribution systems is alternating current (AC). This is the type of electricity that comes from your wall outlets and powers standard household appliances.
Devices called inverters are used on PV panels or arrays to convert DC electricity into AC electricity. Without an inverter, the energy your panels produce cannot run most of the things in your home unless the device is specifically designed for DC input. The EIA notes that inverters can be used on individual panels or on whole arrays.
Batteries store energy for later
A PV system can also charge a battery, the EIA states, to provide electricity when the sun is not shining. This works for individual devices, single homes, or even electric power grids. The DOE reinforces that one challenge facing solar energy is reduced energy production when the sun sets or is blocked by clouds, and it names thermal energy storage as one solution, a method used with large concentrating solar plants rather than small setups. For small-scale beginners, a battery simply acts as a reservoir, holding DC electricity until you need it. Understanding energy storage is a key part of Energy Awareness when planning any solar project.
Why solar output changes
Solar panels do not always produce the same amount of power. The EIA identifies several factors that affect available sunlight: time of day, location, season, and weather conditions. A panel that produces significant electricity at noon on a clear summer day will produce far less on an overcast winter morning. The EIA also explains that PV cells and panels produce the most electricity when they are directly facing the sun. While tracking systems exist to keep panels pointed at the sun, they are expensive. Most PV systems use a fixed position, usually facing directly south in the northern hemisphere, at an angle that optimizes performance.
How panel efficiency has improved
The efficiency of a solar panel tells you how much of the sunlight hitting it gets converted into usable electricity. The EIA provides a clear timeline of efficiency gains: commercially available PV panels averaged less than 10% efficiency in the mid-1980s. By 2015, that figure had increased to around 15%. Today, state-of-the-art modules are approaching 25% efficiency. Experimental cells for niche uses, such as space satellites, have achieved nearly 50% efficiency, but those figures do not represent what you would buy for a home setup. This steady improvement is a key reason why small-scale solar has become more practical over time, as we discuss in Solar Myths and Facts.
Grid-connected vs off-grid systems
When you read about solar, you will frequently see the terms grid-connected and off-grid. The EIA explains that PV systems can supply electricity in locations where power lines do not exist, which is called off-grid. The first practical PV cell was developed in 1954, and by the late 1970s panels were providing electricity in remote, off-grid locations. Since 2004, most PV systems in the United States have been grid-connected, meaning they are linked to an electric power grid. The EIA notes that millions of grid-connected PV systems are now installed across the country. A grid-connected system allows you to use electricity from the grid when your panels are not producing enough and, in many setups, send excess power back to the grid.
For beginners interested in experimenting without a full home installation, our Portable Solar Basics guide covers small, manageable setups.
A short glossary: watt, kilowatt, kilowatt-hour
The EIA’s guide to measuring electricity provides clear definitions for these units. Understanding these three terms is essential for reading any solar specification sheet.
| Term | What it means |
|---|---|
| Watt (W) | The unit of electrical power. The EIA says watts measure power at a specific moment, and that one watt is a very small amount of power. |
| Kilowatt (kW) | One thousand watts. The EIA says devices that need larger amounts of power have their consumption measured in kilowatts. |
| Kilowatt-hour (kWh) | The amount of energy from using one kilowatt of power for one hour. Electricity consumption and generation over time are measured in kilowatt-hours. |
Worked example: powering a small light
Imagine you have a 10-watt LED light bulb and you want to keep it on for 5 hours. The energy required is 10 watts multiplied by 5 hours, which equals 50 watt-hours, or 0.05 kilowatt-hours. A panel rated at 50 watts would need to deliver its full rating for a whole hour to supply those 50 watt-hours. In practice output changes with the sun, as explained above, so a beginner should plan for a panel to deliver less than its rating.
This kind of simple arithmetic helps when planning any project. Our Beginner Calculators can walk you through these calculations step by step.
Common myths handled with source facts
Myths about solar energy can confuse beginners. Here are some statements clarified with information from the official sources.
Myth: Solar panels do not work on cloudy days. The EIA states that the amount of available sunlight depends on weather conditions, among other factors. The DOE also notes that reduced energy production is a challenge when the sun is blocked by clouds. So the accurate statement is that clouds reduce production; how much depends on the conditions.
Myth: A solar panel can power your entire house on its own. The EIA explains that one PV cell produces only 1 or 2 watts. Panels are connected in arrays to produce electricity for an entire house, and some PV power plants cover many acres to generate electricity for thousands of homes. A single panel is just one building block; it takes an appropriately sized array to meet whole-home demand.
Myth: Solar panels are a new, unproven technology. According to the EIA, the first practical PV cell was developed in 1954 by Bell Telephone researchers, and beginning in the late 1950s PV cells were used to power U.S. space satellites. The technology has been in use since the 1950s.
For more clarity on common misconceptions, visit our dedicated Solar Myths and Facts page.
Frequently asked questions
Do I need a battery to use solar panels?
Not necessarily. The EIA states that PV systems can supply electricity directly to the grid or to devices when the sun is shining, and they can also charge a battery for later use. A battery matters when you want stored power for times the sun is not shining, which is why small portable setups and off-grid systems include one.
What is the difference between a solar cell and a solar panel?
According to the EIA, a photovoltaic cell is the basic building block and produces 1 or 2 watts. A PV panel, or module, is a packaged, weather-tight unit made of electrically connected cells and produces more electricity. Panels can be grouped into arrays for even larger output.
Why do solar panels need to face south?
The EIA explains that most PV systems have panels in a fixed position that are usually facing directly south in the northern hemisphere at an angle that optimizes performance. The EIA adds that tracking systems can keep panels facing the sun but are expensive, which is why fixed panels are common. In the southern hemisphere the EIA says panels usually face north.
Ready to learn more? Browse the full Solar for Beginners section for clear, beginner-friendly guides on every aspect of getting started with solar energy.
