Learn about solar energy: Comprehensive guide


The sun sets behind two panel-mounted solar panel arrays
Solar power is the leading renewable energy source.

The star of our solar system — the sun — is constantly sending energy towards our planet. So much, in fact, that in just two hours more energy from the sun falls on the Earth’s surface than all humans collectively consume in an entire year.

With advances in technology, we are now getting better at harnessing this immense amount of energy. Solar energy is now the fastest-growing electricity source in the US, and will make up almost half of all renewable energy generation by 2050. 

This page will tell you everything you need to know about this promising renewable energy source. 

On this page

    Types of solar energy

    Solar energy is any form of energy that is harnessed directly from the sun’s rays. In more technical terms, it refers to the capture of electromagnetic radiation from the sun and its conversion into usable energy, in the form of electricity or heat.

    Solar power: Solar energy as electricity

    Solar power refers specifically to electricity generated from solar energy. Solar power can be generated in one of two ways: 

    • Photovoltaic systems: Photovoltaic (PV) panels (usually just referred to as ‘solar panels’) directly convert the radiation from sunlight into electric current.  
    • Concentrating solar power: This technology uses a large number of special mirrors to concentrate the energy of the sun. The heat is directed to substances that can generate steam; the steam then drives a power turbine to create power.

    ‘Solar photovoltaic (PV) panels’ refer to the technology used by most solar power plants — and all homes — that rely on the sun’s energy for power generation. 

    As of 2019, solar power accounted for 1.7% of all electricity generation in the US. This is still a small share, but the Energy Information Administration predicts solar capacity will grow fast

    Solar thermal: Solar energy as heat

    Solar thermal energy is the heat energy from the sun. Solar thermal energy in its raw form is actually the energy source that sustains life on Earth; it keeps the temperatures at habitable levels and provides energy for plants to grow. 

    Now, thanks to modern technology, we have several new ways to use this heat energy: 

    • Passive solar design: Passive solar design uses the structural elements of a building in order to heat and cool it, in an effort to reduce the use of high-consumption equipment like HVACs. This tech is often referred to as ‘solar heating and cooling’.
    • Solar hot water: This is when you use solar thermal panels to heat up water stored in a cylinder. A properly designed system operates efficiently regardless of outside temperature, and can meet most of a home’s hot water needs.
    • Solar cooking: Solar cooking is one of the simplest examples of solar technology. Solar ovens can be built from a wide range of materials and are capable of reaching temperatures of 400 degrees Fahrenheit or more. 

    Learn more

    Passive solar heating explained
    Are solar water heaters worth the cost?

    Sun enters the house during winter but is blocked by the overhang in the winter. 

    This illustration shows a house that uses two forms of solar thermal: passive solar design and solar water heating. Image source: Kurt Struve 

    From sunlight to electricity: How does solar power work?

    Solar power has a magical quality to it: electrons are grabbed out of thin air and turned into electricity! The process actually replies on simple scientific principles, and is relatively simple to implement. 

    Here’s a brief explanation of how it works; let’s first look at the equipment required, and then see how the components operate together (a more detailed explanation of the process is available here). 

    Necessary equipment to create solar power 

    Here are the main components that go into a solar panel system.

    A solar cell is an electrical device that contains a semiconductor material — generally silicon — that produces electricity through the photovoltaic effect when hit by solar radiation. The energy produced by solar cells is direct current (DC) electricity.

    A solar panel is a collection of solar cells that are attached together in a frame and covered in glass. There are usually 60-72 solar cells in each individual solar panel. Solar panels are also referred to as photovoltaic (PV) panels or solar modules.

    A solar array is multiple solar panels wired together to form a circuit. 

    A solar panel system is the complete setup that provides usable solar electricity. It consists of one or more arrays, which are connected to accompanying equipment including mounting and racking, wiring and a solar inverter. It generates and transmits power in a form that is ready for usage, storage, or to export to the grid.

    Solar cells form a solar panel, solar panels form a solar array, and a solar array with allied equipment makes a solar panel systemThe components of a solar panel system.

    The solar inverter is the most important part of a solar system after the solar panels. The inverter’s job is to receive the DC power generated by the solar array and turn it into AC electricity that can either be used on-site or sent to the grid. 

    How it all works together 

    The solar panels are mounted in a location where they will receive plenty of sunlight. 

    When the sun hits them, the solar cells are activated and generate a DC current. The DC current then travels to the inverter, where it is converted into AC electricity. This AC power is then either used onsite (i.e. by a home) or exported to a grid, from where it can be distributed to others who need power.  

    components of a solar system

    The diagram above shows how the power flows between devices. The orange arrows represent the workings of the solar panel system, as described above. The blue arrows, meanwhile represent power imported from the grid - useful for when solar can’t meet energy demand, for example, during the night.

    Learn more

    How do solar panels work? 
    How does solar energy work and how do we use it in our homes? 
    Wiring solar panels: Do you wire solar panels in series or parallel? 

    Is solar energy a renewable energy source?

    Solar energy is considered renewable because it does not deplete the finite resources of the earth. Harnessing solar energy for warmth or electricity doesn’t reduce its supply — no matter how much we use, the sun will continue to shine! 

    Solar is also a clean energy source. When solar panels convert sunlight into electricity, nothing is burned, and no emissions or waste are released into the atmosphere.

    This combination of characteristics — that solar is both a renewable and clean source of energy — means that it is a key component in humanity’s efforts to combat climate change. 

    It’s worth drawing a contrast between solar energy and our traditional energy sources - fossil fuels. Fossil fuels are not renewable: there’s only so much of these materials in the ground, and every time you use some there is less left on the Earth. Even worse, coal and natural gas are dirty. When they are burned to generate electricity, they release CO2 in the atmosphere, and 97% of scientists agree that CO2 emissions are what’s causing catastrophic climate change. 

    Learn more: Why solar energy is vital to the future of the planet 

    If you’re curious to learn more about solar and renewable energy series, check out our series on the pros and cons of each: 

    Solar energy pros and cons
    Geothermal energy pros and cons
    Hydroelectric energy pros and cons
    Biomass energy pros and cons
    Tidal energy pros and cons
    Wave energy pros and cons

    Foreground: ground mounted solar panels; background: the sun rises behind a city skyline.

    Solar power is an excellent energy source for homes

    If you are a homeowner who wants to save money — and reduce your carbon footprint in the process — consider installing rooftop solar panels. 

    Unlike other energy sources like wind and hydropower, solar is affordable, easy to install, and available anywhere the sun shines, which is pretty much everywhere.  

    Furthermore, for most homeowners, using solar power to meet their energy needs is much cheaper than relying on their utility company.  

    In many states, you can now see savings of up to $70,000-$100,000 over the lifetime of your solar panel system.

    The calculator below will show you total costs, savings, and even the total reduction in C02 emissions you can achieve. I encourage you to try it out to see if solar power is right for you. 

    Find out how much you can save by going solar. See local rebates and incentives!

    Importance of the solar energy industry in 2021

    In 2020, more than 2 million homes had solar panels installed on them, and the number continues to grow.

    The majority of solar power production is for utility-scale solar projects that have many megawatts (a megawatt is 1,000 kW) of solar panels each. There are more than 81.4 gigawatts (GW) of solar installed in the U.S., enough to power more than 15.7 million homes.

    The solar industry employs more than 250,000 people in all 50 states, making it one of the nation’s most significant sources of employment.

    A breakdown of jobs in the solar industry, compiled by The Solar Foundation.

    The future of solar energy

    Over the past decade, solar energy has exploded in the US, thanks to falling prices and evolving solar energy technologies. Solar panels are now more efficient than ever, while selling for ever-lower prices. 

    The record-low prices of solar, combined with the 26% federal tax credit, make 2021 the cheapest year to go solar yet.

    There will be a jump in prices in 2024 as the federal tax credit expires, but the long-term trend is that solar prices will continue to go even lower in the years and decades ahead. 

    In fact, the cost of solar energy is predicted to fall so low that fossil fuels won’t be able to compete. As we continue to focus on building clean energy infrastructure, we will see a greener, cleaner, and cheaper future! 

    Find out if solar is worth it for your home

    Key takeaways

    • Solar energy can be used in two forms: as solar power (i.e. electricity) or as solar thermal, which refers to heat.
    • Solar energy systems are setups that are meant to harness sunlight and convert it into usable electricity for homes and businesses.
    • Solar power is completely renewable. It is also a clean energy source that emits no carbon. It is considered a key technology in combating climate change.
    • Solar power is the only renewable energy source that’s practical to use in most homes, and solar panel installations can deliver big financial savings.
    • The solar industry is growing fast and currently employs a quarter of a million Americans.
    • Solar will continue its explosive growth in coming years. 2021-2023 will be the cheapest years for solar, but prices may spike in 2024 with the expirations of the federal tax credit.

    Solar learning resources

    Solar energy is a vast topic, and there’s only so much we could cover in a single article. If you want to learn more, here are links to articles about solar energy most commonly-requested by our readers: 

    Is solar energy worth it? 

    Incentives and rebates

    Solar power basics 

    Solar energy storage 

    Solar companies 

    Solar-powered devices and gadgets 

    This guide to solar energy and solar power draws on training materials from Solar Energy International, the leading solar job training organization in the United States.

     - Author of Solar Reviews

    Zeeshan Hyder

    SolarReviews Blog Author

    Zeeshan is passionate about promoting renewable energy and tackling climate change. He developed these interests while studying at beautiful Middlebury College, Vermont, which has a strong focus on sustainability. He has previously worked in the humanitarian sector — for Doctors Without Borders — and in communications and journalism.

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