What Is Solar Energy? Solar Energy vs Solar Power Explained

Quick answer

Solar Energy is the light and heat the sun gives off. People capture it to make electricity with photovoltaic panels, or to heat water and air with solar-thermal collectors.

On a home it almost always means panels on the roof or the ground that turn sunlight into electricity. The house uses that power first, and the grid takes any extra.

Quick facts

The key facts about solar energy, with sources:

What it is: Radiant energy from the sun (light and heat) ¹
Two ways to use it: Photovoltaic (sunlight → electricity) and solar thermal (sunlight → heat) ⁶
Energy is measured in: Kilowatt-hours (kWh)
Power is measured in: Watts or kilowatts (kW)
US utility-scale share, 2025: About 7% of utility-scale generation (solar PV and solar thermal plants) ⁵
US small-scale (rooftop-size) solar, 2025: About 93 billion kWh ²
Energy payback: A PV system makes back the energy used to build it in about 1 to 4 years ⁴

Key takeaways

Solar energy is sunlight put to work, either as electricity (PV) or as heat (solar thermal).
Power is the rate, in kW. Energy is the amount over time, in kWh. Your bill is set by kWh.
Output changes with time of day, season, weather, shade and where you live.
A normal grid-tied system shuts off in a blackout. Backup needs a battery.
The federal 25D homeowner credit ended for systems placed in service after 31 December 2025.
How your utility pays for extra power often matters more than panel brand.

Two ways the sun becomes useful energy

Sunlight reaches Earth as radiation, which is energy that travels as light. There are two practical ways to catch it.

Photovoltaics turn light straight into electricity. When sunlight hits the cells in a panel, it frees tiny charges called electrons. They flow out as direct current (DC), which is power that moves one way. Every home solar electric panel works like this. The photovoltaic page explains the physics.

Solar thermal turns light into heat. On a house that means a solar water heater. At power-plant scale, mirrors focus sunlight on a receiver to make steam for a turbine. The US Department of Energy notes these plants are usually large.

Sources: [6] [1]

How solar energy reaches your outlets

Sunlight → solar panels make DC electricity
DC → an inverter changes it to AC, the kind your outlets use
AC → your electrical panel feeds the home’s circuits first
Extra power → sent through the meter to the grid (a grid-tied system) or stored in a battery
Night or heavy cloud → the home draws from the grid or the battery

What changes how much energy you get

The EIA says places closer to the equator and with dry climates get the most sunlight. The US Southwest gets the most. Seasons matter more the farther you live from the equator.

Sunlight is strongest around solar noon on a clear day. Clouds, dust, smoke and pollution cut it down. So do trees, buildings and hills that cast shade on the panels.

PV panels can use both direct sun and scattered light from a hazy sky. Mirror-based solar plants need direct sun, which is why they sit in deserts. The measure of sunlight hitting a surface is called solar irradiance.

Sources: [3]

Types of solar energy systems

The same sunlight, used five different ways.
Type	What it makes	Where you see it
Rooftop PV	Electricity for one building	Rooftop solar on homes and shops
Ground-mount PV	Electricity, when the roof is shaded or small	Ground-mounted arrays on rural land
Off-grid PV	Electricity with no utility link, stored in batteries	Off-grid cabins and homes
Solar water heating	Hot water	Roof collectors tied to a storage tank
Utility-scale plants	Electricity sold to the grid	Large PV farms and mirror-based thermal plants ¹

Solar energy vs solar power

People use the two phrases the same way. On a quote, a bill or a data sheet they mean different numbers.
	Solar power	Solar energy
What it measures	The rate of production right now	The amount made over a period
Unit	Watts (W) or kilowatts (kW)	Watt-hours or kilowatt-hours (kWh)
Where you see it	Panel wattage, system size (for example "8 kW DC"), inverter rating	Your utility bill, the "estimated annual production" line, your app’s daily total
Simple picture	How fast water flows from a tap	How much water filled the bucket
What it tells you	How big the equipment is	How much of your bill it can cover

Example: reading power and energy off one proposal

Say a proposal lists a system as “20 × 435 W panels” with an annual production estimate. The panel rating below comes from a current Qcells data sheet. The rest is simple math.

Line on the proposal	Math	Power or energy?
Panel rating	435 W per panel at standard test conditions ¹⁵	Power
System size	20 × 435 W = 8,700 W = 8.7 kW DC	Power
Annual production estimate	Modelled from your location, roof angle and shade, in kWh per year	Energy
Bill offset	Annual production (kWh) ÷ your annual use (kWh)	Energy ÷ energy

Two proposals with the same kW can promise different kWh. The kWh line is the one that pays you back. Compare it, and ask how it was modelled. Many installers use NLR’s free PVWatts tool, which bases its range on 30 years of weather data ¹⁰.

Where solar energy is used in the US

Solar PV and solar-thermal plants supplied about 7% of US utility-scale electricity in 2025, the EIA says. That number leaves out rooftop systems. The EIA counts those on their own as small-scale solar, meaning systems under 1,000 kW.

Small-scale solar made about 93 billion kWh in 2025. Utility-scale solar made about 292 billion kWh the same year. Texas and California led utility-scale solar, with about 20% and 18% of capacity.

Most US PV systems have been tied to the power grid since 2004, the EIA notes. Before that, panels were mostly used in remote spots with no power lines. State-by-state numbers are in our solar energy statistics roundup.

Sources: [5] [2] [3]

Benefits and limits of solar energy

Benefits

No air pollution or greenhouse gases while it runs.
No fuel to buy. Sunlight costs nothing.
Panels have no moving parts, so there is little to wear out.
Makes power where you use it, so less is lost on long power lines.
Can work where there are no power lines at all.

Limits

Output rises and falls with time of day, season and weather.
It takes a lot of surface area to collect a useful amount.
No power at night unless you add a battery or use the grid.
Making panels uses energy and some hazardous chemicals.
Your savings depend on your utility’s rules for exported power.

Sources: [1] [4]

Limits you will hit at home

Roof space sets a ceiling. A small roof, or one that faces north, may not fit enough panels to cover your use. A ground mount can help if you have open land.

Shade cuts output. Even part of a panel in shade can drag down a whole string of panels on some designs. Our guide to shade and solar output shows why.

Utility rules cap system size and set how you are paid for extra power. Some utilities pay less for exported power than they charge you. A bigger system is not always a better deal.

What drives the cost of solar energy

We do not print a single price, because quotes vary by home. The main cost drivers are system size in kW, panel and inverter type, roof work, permits and labor. A battery adds a large separate cost. Our solar cost guide and cost per watt guide break these down.

Lifespan affects value too. The DOE cites a Berkeley Lab survey: the average working life of a panel grew from about 20 years in 2007 to 25–35 years in 2025. Inverters often need replacing sooner than panels. Warranty terms are set by each maker, so read the data sheet.

Tax credits changed. The IRS says the federal 25D homeowner credit "is not available for any property placed in service after December 31, 2025." Do not trust a quote that still promises it. State credits may still apply, such as South Carolina’s.

Sources: [8] [9]

How a home goes solar, step by step

The path is much the same in most places. A licensed installer and electrician do the work.

Check your roof, shade and last 12 months of power use. Mapping tools can show if the roof suits solar ⁷.
Get several quotes. Compare the kWh estimate, the equipment and the warranty, not only the price.
Pick a qualified installer. DOE suggests looking for NABCEP certification ⁷. Check the state license too.
The installer draws plans and applies for a building and electrical permit from your city or county.
The installer applies to your utility to connect, which is called interconnection.
Crews mount the racking, panels, inverter and wiring.
A local inspector checks the work against the building and electrical codes.
The utility swaps or sets the meter and gives permission to operate. Only then do you switch on.

Our permission to operate guide explains that last step.

Keeping a solar energy system working

Panels need little care because nothing moves. The main job is to watch your monitoring app. Compare this month’s kWh to the same month last year. A sudden drop is worth a call.

Rain clears most dust. Heavy pollen, bird droppings or dust in dry areas can cut output. Do not climb on the roof. Our panel cleaning guide covers safe options, or you can book panel cleaning.

Plan for the inverter. It does more work than the panels and often fails first. The inverter replacement planner helps you budget.

Warning signs and when to call a pro

Call your installer or a licensed electrician if you see any of these. Do not open panels, boxes or wiring yourself. Solar wiring can stay live in daylight.

Your app shows zero output on a sunny day.
An error light or code on the inverter.
A burning smell, scorch marks or buzzing near any solar part.
Cracked glass, loose panels or wires hanging under the array.
Water stains on the ceiling under the panels.
Your bill rises with no change in how you use power.

Safety rule

Panels make power whenever light hits them. Only a licensed electrician or installer should work on any part of the system.

Rules that apply to solar energy at home

Building and electrical codes. Your city or county enforces the codes it has adopted. In South Carolina, the 2021 state building codes (based on the 2021 IRC and IBC) are in force, per the SC Building Codes Council. Ask your installer which code edition your permit uses.

Federal tax. The IRS ended the 25D Residential Clean Energy Credit for property placed in service after 31 December 2025. Leased systems may use a separate business credit, 48E. Ask a tax professional.

Utility rules. Each utility sets its own connection steps, size caps and export credits under rules from its state regulator. See our interconnection guide.

Sources: [9] [11] [7]

Misconceptions

Myth Solar panels store the sun’s energy.: Reality Panels turn light into electricity the instant it hits them. Storing it takes a separate battery.
Myth More solar power always means a lower bill.: Reality The bill moves with energy (kWh) and with how your utility pays for exports. A large system on a low export rate can save less than expected.
Myth Solar energy keeps the lights on in a blackout.: Reality A standard grid-tied system shuts off when the grid fails, by design. Backup needs a battery or a hybrid system.
Myth Solar does not work in cloudy places.: Reality PV uses scattered light too. Output is lower, and production estimates already include local weather ³.
Myth Making panels uses more energy than they produce.: Reality The EIA says a PV system makes back its manufacturing energy in about 1 to 4 years ⁴.

Solar energy in SC, GA and VA

Each state pays for exported solar power its own way. In South Carolina, homes that applied before 1 June 2021 keep legacy net metering until 31 May 2029; later ones use a Solar Choice tariff (Act 62 of 2019) ¹².

SC also has a state income tax credit for solar (SC Code §12-6-3587). Georgia Power limits residential renewable systems to 10 kW ¹³. Virginia law allows residential net metering up to 25 kW on investor-owned utilities ¹⁴.

Is solar energy right for your home?

Solar tends to make sense when most of these are true:

Your roof or yard gets good sun for most of the day.
The roof is sound, or you plan to replace it before solar.
You expect to stay in the home for years.
Your utility gives fair credit for extra power, or you use most power in the day.
You can pay cash or get a loan at a fair rate.

Next steps

Solar system size calculatorTurn your yearly kWh into a kW size
Solar savings calculatorSee what your bill could look like
How home solar worksThe full path from sunlight to outlet

Questions about solar energy

Is solar energy renewable?

Yes. It comes from sunlight, which comes back every day. The EIA lists solar among the renewable energy sources it tracks. Making the panels does use energy and materials. The EIA says a PV system makes back the energy used to build it in about 1 to 4 years, then keeps producing for decades.

Is solar power the same thing as solar energy?

In everyday speech, yes. Technically, power is the rate, in kW, and energy is the amount over time, in kWh. A system’s size is its power. What it makes in a year is its energy. Your bill is based on energy, so the kWh number matters most.

Does solar energy work on cloudy days?

Yes, but less. Clouds scatter and absorb sunlight before it reaches the panel. PV panels can still use that scattered light. A good annual estimate already includes your typical local weather, so cloudy days are built in. Snow on the panels stops output until it slides off.

What are the main disadvantages of solar energy?

Output varies with time of day, season, place and weather, and it takes a lot of space to collect. The EIA names both. At home, the real limits are roof space, shade, and how your utility credits exported power. A standard system also shuts off in a blackout.

What is the difference between solar PV and solar thermal?

Solar PV makes electricity straight from light. Solar thermal makes heat. At home that heat warms water in a tank. At power plants, mirrors focus sunlight to make steam that spins a turbine. Most people who say “going solar” mean PV.

Can solar energy power a whole house?

It can cover all of a home’s yearly use if the roof is big and sunny enough. It still cannot run the house at night without a battery or the grid. Most homes stay on the grid and use it as a backstop. A size calculator shows how many kW your use needs.

How long do solar panels last?

The DOE cites a Berkeley Lab survey that puts the average working life at 25 to 35 years for panels in 2025. That is up from about 20 years in 2007. Inverters usually wear out sooner. Check the maker’s warranty on your own data sheet, since terms vary.

Is there still a federal tax credit for home solar?

Not for homeowners who own the system. The IRS says the 25D credit is not available for property placed in service after 31 December 2025. Leased systems may still use a business credit. Some states, such as South Carolina, still have their own credit. Ask a tax professional.

Does solar energy work during a power outage?

A normal grid-tied system shuts down when the grid goes down. This protects line workers fixing the lines. To keep power on, you need a battery and equipment that can separate your home from the grid. A licensed installer sets this up.

Where in the US is solar energy strongest?

The Southwest gets the most sunlight, the EIA says. Lower latitudes and dry climates get more sun in general. Solar still works across the whole country. Shade, roof angle and local power prices often matter as much as sunshine to whether it pays off.

Sources

US EIA, Solar explained, retrieved October 7, 2026.
US EIA, Solar explained: Photovoltaics and electricity, retrieved October 7, 2026.
US EIA, Solar explained: Where solar is found and used, retrieved October 7, 2026.
US EIA, Solar explained: Solar energy and the environment, retrieved October 7, 2026.
US EIA, Electricity explained: Electricity in the United States, retrieved October 7, 2026.
US DOE Solar Energy Technologies Office, How Does Solar Work?, retrieved October 7, 2026.
US DOE Solar Energy Technologies Office, Homeowner’s Guide to Going Solar, retrieved October 7, 2026.
US DOE Solar Energy Technologies Office, End-of-Life Management for Solar Photovoltaics, retrieved October 7, 2026.
IRS, Residential Clean Energy Credit (§25D), retrieved October 7, 2026.
National Laboratory of the Rockies (NLR), PVWatts Calculator, retrieved October 7, 2026.
SC Building Codes Council, code adoption, retrieved October 5, 2026.
South Carolina Code Title 58 Ch. 40 (Act 62 of 2019, customer-generators), retrieved October 5, 2026.
Georgia Power, Behind-the-Meter Interconnection Summary for Residential Customers (rev. 15 Aug 2025), retrieved October 7, 2026.
Code of Virginia §56-594 (net energy metering), retrieved October 7, 2026.
Qcells, Q.TRON BLK S-G3R.12+/BFG 435–450 W data sheet (2025-08 Rev04), retrieved October 7, 2026.

Expert review

Written by the HyreSolar Research team. Not yet reviewed by an outside expert. We say so rather than imply a review that has not happened; see our editorial policy.

How the numbers were checked: Definitions, generation figures, resource and environmental facts are from the EIA and DOE pages cited, read on the retrieval date. Tax status is from the IRS 25D page.

SC facts come from sc-local/facts.js (retrieved 5 Oct 2026); GA and VA limits from the Georgia Power summary and Va. Code §56-594. The example is arithmetic on a data-sheet panel rating.

Suggest a correction. We fix errors and say what changed.