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How solar panels work
Start here. No physics background needed, and no jargon that isn’t explained the moment it appears.
The short answer: sunlight hits silicon and knocks electrons loose. Moving electrons are electricity. A box called an inverter converts that into the kind of electricity your house runs on, and it flows into your breaker panel like any other power. Whatever you don’t use goes out to the grid.
The whole thing in one picture
Step by step
1. Sunlight hits the panel
A solar panel is mostly a sheet of silicon — the same material in computer chips, refined from ordinary sand — under glass, in an aluminum frame. Silicon has a useful property: when light strikes it, the energy knocks electrons loose from their atoms.
The panel is built so those loose electrons can only travel one direction. That one-way flow of electrons is the electricity. Nothing moves, nothing burns, nothing wears out in the process. It’s why panels are so reliable — there are no moving parts to break.
2. The panel produces DC electricity
What comes out is direct current, or DC — electricity that flows steadily in one direction. It’s what batteries produce. Your phone, your flashlight and your car all run on DC.
Your house does not.
3. The inverter converts DC into AC
Household wiring uses alternating current, or AC, which rapidly reverses direction many times a second. Every outlet in your home is AC. So the DC from your roof has to be converted, and the box that does it is the inverter.
The inverter is the brain of the system and the part most likely to need replacing during the system’s life. Panels routinely outlast it. There are two common arrangements:
- A string inverter — one box, usually mounted near your breaker panel, handling every panel together.
- Microinverters — a small inverter behind each individual panel, so panels work independently. Costs more, but handles partial shade better, because one shaded panel doesn’t drag down its neighbors.
Which is right for you depends mostly on shade. There’s a fuller comparison on the inverters page.
4. It flows into your breaker panel
From the inverter, the AC electricity feeds into your home’s existing breaker panel — the gray metal box with all the switches. From there it travels through the same wires as always. Your lights, your refrigerator and your outlets can’t tell the difference and don’t need to.
Your home uses solar power first, automatically, before drawing anything from the utility. There’s no switch to flip and nothing to manage.
5. Surplus goes out to the grid
At midday your panels usually produce more than you’re using. That surplus flows backward through your meter and out to the grid, and your utility credits you for it. At night, when the panels produce nothing, you draw power back from the grid as normal.
The rules for how you’re credited are called net metering, they vary enormously by state and utility, and they matter a great deal to whether solar pays off where you live. That has its own page.
Four things almost everyone gets wrong
“The panels store power for later.”
They don’t. A standard solar system stores nothing at all. It produces electricity when the sun is on it and produces none when the sun isn’t. Storing power requires a battery, which is a separate purchase that can nearly double the cost of a project.
Without a battery, the grid does your storing: you push power out during the day and pull it back at night.
“If the power goes out, I’ll still have electricity.”
Not with a standard grid-connected system. When the utility loses power, your solar system shuts itself off — even at noon on a cloudless day, even though the panels are perfectly capable of producing.
This is deliberate and it is a safety feature. If your system kept pushing electricity into the neighborhood wires during an outage, it could electrocute the line workers repairing them. Every grid-tied inverter is required to detect an outage and stop.
To have power during an outage you need a battery and equipment that isolates your house from the grid. If backup power is your main reason for wanting solar, learn this before you sign anything — it is the single most common unpleasant surprise in residential solar.
“Solar only makes sense somewhere hot.”
Panels run on light, not heat, and heat actually works against them. A solar panel is more efficient on a cold, clear winter day than on a hot summer one — typically several percent better at freezing than at high summer cell temperatures.
Cold, sunny places are excellent for solar. Germany, which is not famous for sunshine, was for years among the world’s largest solar markets. What matters is hours of light, not degrees of warmth.
“Clouds mean nothing.”
Output drops but doesn’t stop. Panels use diffuse light — sunlight scattered by cloud — as well as direct light. Typical figures:
Partly cloudy: roughly 50–80% of rated output. Heavy overcast: roughly 10–25%. Panels buried under snow: essentially zero, until it slides off, which it usually does before long because the glass is smooth and tilted.
Across a winter, expect daily production somewhere around half to two-thirds of what you get in summer — driven mostly by shorter days and a lower sun angle, not by the cold.
How long do they last?
Panels don’t fail on a particular date. They slowly produce a little less each year, a process called degradation. Good modern panels lose roughly 0.3% to 0.5% per year.
Compounded over 25 years, that rate leaves a panel producing roughly 88% to 93% of what it did when new.
What manufacturers guarantee is lower — commonly around 85% to 87% at year 25. That gap isn’t a contradiction. Warranties are deliberately conservative, and they allow for a larger drop in the first year, which is normal for silicon panels. In practice, panels tend to outperform their warranty. The guaranteed figure is the floor, not the expectation.
Two warranties come with panels, and they are not the same thing:
- Product warranty — covers the panel physically failing or being defective. Commonly 25 years now.
- Performance warranty — guarantees the panel still produces at least a stated percentage of its original output by a given year. Commonly 25 years, sometimes 30.
The catch nobody mentions
A 25-year warranty is only worth as much as the company standing behind it. Solar manufacturers and installers do go out of business, and when they do, the warranty usually goes with them.
When comparing equipment, how long the company has existed and how financially solid it is matter at least as much as the number of years printed on the warranty.
What “efficiency” actually means
You’ll see panels advertised as 20% or 22% efficient. That figure is simply the percentage of the sunlight landing on the panel that gets turned into electricity. Most residential panels in 2026 fall between 20% and 22%, with premium models reaching about 24%.
It matters less than the marketing implies. Efficiency tells you how much roof space you need for a given amount of power — not how much money you’ll save. A more efficient panel produces more per square foot, so you need fewer of them.
That’s genuinely valuable if your roof is small or awkward. If you have plenty of room, paying a premium for high efficiency often buys you nothing but a slightly smaller array. What you actually care about is the total kilowatt-hours the whole system produces per dollar you spent.
Sources
- A1 SolarStore, How efficient are solar panels: 2026 performance guide.
- Energy Solutions, Solar panel degradation rates 2026.
- GreenLancer, Solar panel warranty guide — product vs. performance warranties.
- PowerOutage.us, Do solar panels work on cloudy days?
- PowerOutage.us, Do solar panels work in winter?
- EnergySage, Solar panel output.