Updated in July 2026
Every time sunlight touches your skin, warms a rooftop, or charges a solar battery, you are experiencing radiant energy in action. It is one of the most fundamental forms of energy in the universe — and the very thing that makes solar power possible. Radiant energy is energy that travels as electromagnetic waves, including visible light, infrared heat, and ultraviolet rays. It can move through empty space without needing any matter to carry it, which is exactly how the Sun’s energy reaches Earth.
In this guide, the team at Energy Matters explains what radiant energy is in plain language, gives everyday examples, compares it to other energy types, and shows how Australian solar systems convert it into the electricity that powers your home.
Key takeaways (TL;DR)
- Radiant energy is energy carried by electromagnetic waves — light, infrared, ultraviolet, microwaves, and radio waves — that can travel through the vacuum of space.
- The Sun is the largest natural source of radiant energy reaching Earth, making it the foundation of solar power.
- Earth receives about 1,361.6 W/m² of solar radiant energy at the top of the atmosphere, which averages to roughly 340 W/m² across the whole planet.
- Common examples include sunlight, heat lamps, microwaves, X-rays, and the warmth from a campfire.
- Solar panels convert radiant energy into electricity through the photovoltaic effect — first discovered in 1839.
- Australia’s high solar irradiance makes radiant energy especially valuable for homes and businesses.
What is radiant energy?
Radiant energy is the energy of electromagnetic waves and is one of several basic forms of energy. It travels as oscillating electric and magnetic fields — or equivalently as particles of light called photons — and, unlike heat conducted through a metal rod, it does not need a physical medium to move. This is why the Sun’s radiant energy can cross 150 million kilometres of empty space to reach Earth.
The amount of radiant energy is measured in joules, and the rate at which it flows (radiant power, or flux) is measured in watts. When that power lands on a surface — like a solar panel — it is described as irradiance, measured in watts per square metre (W/m²). For reference, NASA’s TSIS-1 mission anchors the Sun’s total solar irradiance at about 1,361.6 ± 0.3 W/m² at the top of Earth’s atmosphere.
What is radiant energy?
Radiant energy is the energy of electromagnetic waves and is one of several basic forms of energy. It travels as oscillating electric and magnetic fields — or equivalently as particles of light called photons — and, unlike heat conducted through a metal rod, it does not need a physical medium to move. This is why the Sun’s radiant energy can cross 150 million kilometres of empty space to reach Earth.
The amount of radiant energy is measured in joules, and the rate at which it flows (radiant power, or flux) is measured in watts. When that power lands on a surface — like a solar panel — it is described as irradiance, measured in watts per square metre (W/m²). For reference, NASA’s TSIS-1 mission anchors the Sun’s total solar irradiance at about 1,361.6 ± 0.3 W/m² at the top of Earth’s atmosphere.
What type of energy is radiant energy?
Radiant energy is the energy of electromagnetic waves and is one of several basic forms of energy. It travels as oscillating electric and magnetic fields — or equivalently as particles of light called photons — and, unlike heat conducted through a metal rod, it does not need a physical medium to move. This is why the Sun’s radiant energy can cross 150 million kilometres of empty space to reach Earth.
The amount of radiant energy is measured in joules, and the rate at which it flows (radiant power, or flux) is measured in watts. When that power lands on a surface — like a solar panel — it is described as irradiance, measured in watts per square metre (W/m²). For reference, NASA’s TSIS-1 mission anchors the Sun’s total solar irradiance at about 1,361.6 ± 0.3 W/m² at the top of Earth’s atmosphere.
Examples of radiant energy in everyday life
The most common example of radiant energy is sunlight, but it surrounds us in many everyday forms. Any device or source that emits light, heat, or other electromagnetic waves is releasing radiant energy.
- Sunlight — the visible light and warmth that reaches Earth from the Sun.
- Infrared (heat) lamps — used to keep food warm or heat outdoor areas.
- Microwaves — used to cook food and transmit signals.
- Radio waves — broadcasting music, television, and mobile signals.
- X-rays — used in medical imaging to see inside the body.
- A glowing campfire or light bulb — emitting both visible light and infrared heat.
Radiant energy is also central to nature. During photosynthesis, plants capture the Sun’s radiant energy and convert it into chemical energy stored as sugars — the same process that ultimately fuels nearly all life on Earth.
Radiant energy vs Thermal energy vs Electrical energy
Radiant energy travels as electromagnetic waves through space, thermal energy is the internal heat of a substance from moving particles, and electrical energy is the movement of electric charge through a conductor. Solar power links all three: radiant energy from the Sun is converted into electrical energy, which can then produce thermal energy (heat) in your home.
Property | Radiant Energy | Thermal Energy | Electrical Energy |
How it travels | Electromagnetic waves / photons | Particle motion & conduction | Flow of electric charge |
Needs a medium? | No — travels through a vacuum | Usually yes | Yes — a conductor |
Everyday example | Sunlight, microwaves | A hot stovetop | Power in your home |
Solar relevance | ✔ The input for solar panels | ✔ Solar hot water & heating | ✔ The output of PV panels |
Does the sun produce radiant energy?
Yes — the Sun is the most powerful natural source of radiant energy reaching Earth. Through nuclear fusion in its core, the Sun continuously emits enormous amounts of electromagnetic radiation, a small fraction of which travels to Earth and drives our weather, climate, and renewable solar power.
When that radiant energy reaches the planet, NASA estimates about 29% of incoming solar energy is reflected back to space, leaving roughly 71% absorbed by the Earth system (NASA Science – Climate and Earth’s Energy Budget). NASA’s TSIS-1 Spectral Irradiance Monitor measures solar spectral irradiance from 200 to 2,400 nanometres, covering about 96% of total solar irradiance.
How radiant energy becomes electricity in solar panels
olar panels convert radiant energy into electricity through the photovoltaic effect, where photons of sunlight knock electrons loose in a semiconductor (usually silicon), creating an electric current. This is the core process behind every rooftop solar system. The photovoltaic effect was first discovered by Edmond Becquerel in 1839, long before it powered modern homes.
- The Sun emits radiant energy as electromagnetic waves travelling toward Earth.
- The atmosphere filters it, absorbing and scattering some wavelengths before they reach the ground.
- Solar panels absorb the light, with photons striking the silicon cells.
- The photovoltaic effect generates direct current (DC) as electrons are freed and flow.
- An inverter converts DC to AC, which then powers your home, charges a battery, or feeds the grid.
To learn more about the technology behind this conversion, see our guide on the Solar Photovoltaic (PV) System: All You Need To Know. Squeezing the maximum output from incoming radiant energy is also why modern systems use Maximum Power Point Tracking.
Key radiant energy statistics
- Earth’s total solar irradiance is about 1,361.6 ± 0.3 W/m² at the top of the atmosphere (NASA Earth – Solar Irradiance Science).
- Averaged over the whole Earth system, that works out to about 340 W/m² (NASA Earth – Solar Irradiance Science).
- Visible light spans roughly 380–700 nanometres — only a small slice of the full radiant spectrum (NASA Science – Visible Light).
- Greenhouse gases were retaining an extra 3.54 W/m² of heat in 2024 relative to preindustrial conditions, and atmospheric CO₂ reached 422.80 ± 0.10 ppm
- Earth’s observed energy imbalance reached 1.8 W/m² in 2023, according to a 2025 AGU Advances paper hosted by NOAA
Why radiant energy matters for Australian homes
Australia receives some of the highest solar radiant energy in the world, which is why rooftop solar is so effective here. The more radiant energy a region receives, the more electricity its solar panels can produce — turning sunlight into real bill savings.
If your system isn’t capturing as much of that energy as it should, it may be time for a check-up. Our guides on whether your solar system is underperforming and what to do when your 10-year-old system needs a boost can help. Radiant energy also powers thermal solutions — explore the 7 pros of solar hydronic heating to see how the Sun’s heat can warm your home directly.
Conclusion
Radiant energy is the invisible engine behind sunlight, heat, and modern solar power. It travels as electromagnetic waves, surrounds us in everyday devices, and — thanks to the photovoltaic effect — can be transformed into clean electricity for your home or business. With Australia’s abundant sunshine, harnessing radiant energy through solar is one of the smartest moves a household can make.
Ready to put radiant energy to work? Contact us to compare free solar quotes from trusted local installers.
Frequently asked questions
What are 5 examples of radiant energy?
Five common examples of radiant energy are visible light (sunlight), infrared (heat) rays, ultraviolet rays, microwaves, and radio waves. X-rays and gamma rays are also forms of radiant energy.
What does it mean to have radiant energy?
Having radiant energy means energy is being carried by electromagnetic radiation — described either as photons or as waves in oscillating electric and magnetic fields — that can travel through space without a medium.
What is radiant energy in simple terms?
In simple terms, radiant energy is energy that can transfer through empty space as light and other electromagnetic waves without needing matter to carry it — like sunlight reaching the Earth.
What is another name for radiant energy?
Radiant energy is often called electromagnetic energy or electromagnetic radiation, because it is energy carried by electromagnetic waves. Light energy is a closely related term for the visible portion.
How is radiant energy different from solar energy?
Solar energy is the radiant energy that specifically comes from the Sun. All solar energy is radiant energy, but radiant energy also includes other sources like heat lamps, microwaves, and X-rays.
How do solar panels use radiant energy?
Solar panels use radiant energy by absorbing sunlight in silicon cells, where photons free electrons through the photovoltaic effect to create an electric current that is then converted into usable electricity for your home.
Sources and References:
- NASA Science: Solar Irradiance Science, https://earth.gsfc.nasa.gov/climate/projects/solar-irradiance/science
- NASA Science: Visible Light, https://science.nasa.gov/ems/09_visiblelight/
- NASA Science: Climate and Earth’s Energy Budget, https://science.nasa.gov/earth/earth-observatory/climate-and-earths-energy-budget/
- NASA Science: TSIS-1, https://science.nasa.gov/mission/tsis-1/
- NOAA Global Monitoring Laboratory: Annual Greenhouse Gas Index, https://gml.noaa.gov/aggi/aggi.html
- NOAA Repository: AGU Advances, https://repository.library.noaa.gov/view/noaa/71092/noaa_71092_DS1.pdf
