what is solar energy

What is solar energy?

Simply put, solar energy is energy from the sun. It’s the most abundant energy resource on Earth and can be converted from radiant energy from the sun to electrical or thermal energy. We use solar energy for many purposes, such as powering and heating homes, businesses, utilities, and more. Solar power is a renewable resource and, as such, is a critical part of our clean energy future. In this article, we’ll explain what you need to know about solar energy, including how it works and its applications.

Key takeaways about solar energy

  • Solar energy is energy from the sun and is captured with various technologies, including solar panels.
  • There are two main types of solar energy: photovoltaic and thermal. 
  • The “photovoltaic effect” is the mechanism by which silicon solar panels harness the sun’s energy and generate electricity.
  • Want to take advantage of solar energy yourself? Join the EnergySage Marketplace to compare solar quotes for your property.

In this article:

The photovoltaic effect

The sun does more for our planet than just provide light during the daytime – each particle of sunlight (called a photon) that reaches Earth’s surface contains energy that fuels our planet. Solar energy is ultimately responsible  for all of our weather systems and energy sources on Earth, and enough solar radiation hits the surface of the planet each hour to theoretically fill our global energy needs for nearly an entire year.

So where does all of this energy come from? Our sun, like any star in the galaxy, is basically a massive nuclear reactor. Deep in the Sun’s core, nuclear fusion reactions produce huge amounts of energy that radiates outward from the sun’s surface and into space in the form of light and heat.

On Earth, we harness and convert solar power from the sun into usable energy using photovoltaics or solar thermal collectors. Although solar energy only accounts for a small amount of overall global energy use, the falling cost of installing solar panels means that more and more people in more places can take advantage of solar energy. Solar is a clean, renewable energy resource and will play an important part in the global energy future.

What is solar power used for?

There are many solar energy technologies that harness the sun’s energy. The two main ways to use energy from the sun are photovoltaics and solar thermal capture. Photovoltaics are much more common for smaller-scale electricity projects (like residential solar panel installations), while solar thermal capture is typically only used for electricity production on massive scales in utility solar installations. In addition to producing electricity, lower temperature variations of solar thermal projects can be used for heating and cooling.

Solar is one of the fastest-growing and cheapest sources of power in the world and will continue to spread rapidly in the coming years. With solar technology improving each year, the economic benefits of solar improve, adding to the environmental perks of choosing a clean, renewable energy source. In the coming years, we can expect more and more solar and wind power to enter the mix of large-scale power stations, helping to reduce our country’s greenhouse gas emissions and combat climate change.

Photovoltaic solar energy

A common way for property owners to take advantage of solar energy is with a photovoltaic (PV) solar system. With a solar PV system, solar panels (also called solar modules) convert sunlight into electricity that you can use immediately, store in a solar battery, or send to the electric grid for credits on your electric bill (depending on where you live).

Solar panels convert solar energy into usable electricity through a process known as the photovoltaic effect. Incoming sunlight strikes a semiconductor material (typically silicon) in solar cells and knocks electrons loose, setting them in motion and generating an electric current that can be captured with wiring. This current is known as direct current (DC) electricity and needs to be converted to alternating current (AC) electricity using a solar inverter – this is because most of the U.S. electric grid operates using AC electricity, as do most household electric appliances.

Solar energy is captured at many scales using photovoltaics, and installing a solar energy system is a smart way to save money on your electric bill while reducing your dependence on nonrenewable fossil fuels. Large companies and electric utilities can also benefit from photovoltaic solar energy generation by installing large solar arrays that power company operations or supply energy to the power grid.

Storing energy with solar batteries

Solar electricity is great when the sun is shining – but if you want to maximize your grid independence, you’ll need a solar-plus-storage system. With a solar battery, you can charge your battery with excess energy generated by your system, rather than exporting that energy to the grid. Then, at night or if there’s inclement weather, you can use this stored energy to minimize how much electricity you pull from the grid. If you size your solar-plus-storage system accordingly, you can also go “off the grid” – but, unless your electricity consumption is low, you should expect this setup to be quite complicated and expensive!

Solar thermal energy

A second way to use solar energy is to capture the heat from solar radiation directly and use that heat as solar thermal energy. Solar thermal energy has a broader range of uses than a photovoltaic system, but using it for electricity generation at small scales isn’t as practical as using photovoltaics.

There are three general types of solar thermal energy: low-temperature used for heating and cooling, mid-temperature used for heating water, and high-temperature used for electrical power generation.


Low-temperature solar thermal energy systems involve heating and cooling air as a means of climate control, such as in passive solar building design. In properties built for passive solar energy use, the sun’s rays are allowed into a living space to heat an area and blocked when the area needs to be cooled.


Mid-temperature solar thermal energy systems include solar hot water heating systems. In a solar hot water setup, heat from the sun is captured by collectors on your rooftop. This heat is then transferred to the water running through your home’s piping so you don’t have to rely on traditional water heating methods, such as water heaters powered with oil or gas.


High-temperature solar thermal energy systems use concentrated solar power (CSP) to generate electricity on a larger scale. In a solar thermal electricity plant, mirrors focus the sun’s rays on tubes containing a liquid that can hold heat energy well. This heated fluid evaporates water into steam, which then turns a turbine and generates electricity – all using concentrated sunlight!

Solar heating and cooling with heat pumps

As we’ve discussed, you can heat your home or hot water with solar thermal energy – but you can also do so with solar photovoltaic energy by pairing your solar energy system with a heat pump! Instead of generating heat (like in a natural gas or oil heating system), heat pumps work by simply transferring heat from one place to another, allowing them to have high energy efficiency. If you don’t have solar, you can still power heat pumps with electrical energy from the grid, but you’ll save the most by running them on free solar energy produced right at home! Learn more about how to size your solar system to support a heat pump.

Frequently asked questions about solar power

There’s a lot to learn about solar energy – here are a few quick answers to common questions.

How does solar energy work?

Solar power generation starts when solar panels absorb photons, or particles of light, with photovoltaic cells, generating this direct current (DC) energy and then converting it to usable alternating current (AC) energy with the help of inverter technology. AC energy then flows through the home’s electrical panel and is distributed accordingly.

What is solar power used for?

Solar power is used in two main ways: generating electricity (like with rooftop solar panels) or generating thermal energy (like with concentrated solar power plants). For most homeowners, solar panels that convert solar energy to electricity is the best use of solar energy because it allows them to save on electric bills.

How long do solar panels last?

Solar panels usually last for 25 to 30 years before they start to see steeper drops in performance than is useful for many homes. For those almost three decades, however, you’ll be generating free solar electricity from the sun.

How to support solar development

The percentage of renewable energy (including solar) in your utility’s energy mix continues to increase – but significant strides won’t happen overnight. In the meantime, you can support the development of solar farms in your community by subscribing to a community solar farm! Community solar is a great option if you’re a renter or don’t have a good house for solar; it leads to local job creation and will save you between 10 to 15 percent annually on your electric bills. Browse community solar projects near you.

Take advantage of solar energy on your property

The best way for individual property owners to save money with solar energy is to install a home solar photovoltaic system. To find the right system for the right price, you should shop on the EnergySage Marketplace. After signing up, you’ll receive free solar quotes from qualified, pre-vetted solar installers near you. Looking at quotes is a great way to understand offers and compare key metrics such as energy needs met and cost per watt – and, if you just want to explore how much a solar power system might cost, be sure to check out our solar calculator.

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About Emily Walker

With over five years of experience in environmental science and clean energy, Emily is an expert in solar, battery, and energy management technology and policy. She holds a Master of Science in Environmental Science and Policy from Johns Hopkins University and a Bachelor’s Degree in Environmental Science and Biology from Colby College. Emily is always looking for ways to live her life more sustainably and is currently in the process of electrifying her home.