Table of Contents:
Key Takeaways
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Solar panels use silicon photovoltaic cells to transform sunlight into electrical power.
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The panels generate direct current which inverters convert to alternating current for home use.
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Solar systems can store excess power in batteries or return it to electrical grids for credits.
Ever wondered how a solar panel actually creates energy from the sun? It involves exciting electrons and creating current through the photovoltaic effect. It’s complicated, so we’ll explain how it all works here.
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How solar panels work in a nutshell
Solar panels convert sunlight into electricity using the photovoltaic effect. When sunlight hits the silicon cells inside the panel, it excites electrons and creates a DC electric current. An inverter converts this into usable AC electricity for your home or business. You can use the AC electricity right away and store excess energy in a battery or send it back to the grid. Efficiency depends on things like direct sunlight, panel angle, panel type, and temperature.
How does a solar cell work in a photovoltaic system?
A solar cell converts radiant energy from sunlight into electrical energy through two layers of silicon semiconductors. Here’s the basic process.
1. Sunlight energizes silicon layers
The solar cell consists of two layers of silicon: p-type and n-type silicon. The p-type layer has elements like boron or gallium that make electron deficiencies (also called holes). The n-type layer, using elements like phosphorus, has extra electrons. When sunlight (photons) strikes the surface, it excites electrons in the silicon, forming electron-hole pairs.
2. The electric field moves electrons
The junction between the p-type and n-type silicon creates an electric field, which separates and directs the excited electrons. The field pushes free electrons toward the n-type layer while leaving behind holes in the p-type layer, generating an electric potential.
3. Electrons flow as usable electricity
Metal contacts collect the moving electrons and channel them into electrical wires, forming a direct current (DC). This current flows through an external circuit, delivering power to devices and appliances. The electrons then return to the p-type layer, recombining with the holes, completing the cycle.
This continuous movement of electrons creates a steady DC electrical flow. A single solar panel has about 60 to 72 individual cells, and a standard rooftop system has about 16 to 25 panels. So, you could have 1,800 or more solar cells on your roof.
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Converting DC to usable AC power
Home systems include an inverter to convert the DC to alternating current (AC). Why? Well, homes and most businesses run on AC. This type of current alternates at specific intervals which makes it easy to transmit over long distances. It’s also cheaper to generate and control.
The solar inverter uses transistors like field effect transistors (FET) and insulated gate bipolar transistors (IGBTs) to rapidly switch the current direction. The switching current flows through a transformer which accepts it as AC.
The inverter uses precise algorithms to generate a precise output that matches the standard 60Hz grid frequency. Modern inverters convert 95% to 98% of DC to AC.
What you get is AC power that integrates with your household and powers everything from lighting to major appliances. The inverter also makes bidirectional energy possible, so you can export energy to the grid and get net metering credits.
How much power does a solar panel produce?
A single solar panel is usually rated to produce 250 to 450 DC watts under optimal conditions.
When thinking about the output of a whole system, some energy is lost because of wiring resistance, power conversion, and inverter inefficiencies. Typically, a system operates at about 80% of its total capacity in real-world conditions.
To estimate how much electricity a system will generate in a year, multiply the system size (in kilowatts DC) by 0.8 (to account for loss), then by the average sunlight hours per day and 365 days per year.
For example, a 7.5 kW DC system that gets 5 hours of peak sunlight daily would produce about 10,950 kWh annually. (7.5 x 0.8 x 5 x 365). You can find peak sun hour maps online. The average for the U.S. ranges from about 4 to 6.5.
What’s the right system size for me?
To determine the right system size, divide your monthly electricity use (in kWh) by 30 days and then by your area's average sun hours per day. This gives the system's AC size. Since AC power must be converted from DC power, divide the AC size by 0.8 to get the DC system size.
Once you have the total system wattage, you can calculate how many solar panels you need. Divide the system size (in watts) by the wattage of each panel. For example, if you need 7.5 kW DC and use 250W panels, you’d need about 30 panels.
For the most accurate estimate, review your electric bills from the past 12 months to find your average monthly usage. If a full year isn’t available, six months of data can still provide a reasonable estimate.
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How to store solar energy for a power outage
Battery storage takes your solar system to the next level. Without battery storage, you can only use solar energy at the time your panels generate it. But when you have storage, you can be self-sufficient during power outages and use your stored energy at night.
Here's how they work:
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Charging the battery: When your solar panels produce more electricity than your home is using at the moment, a charge controller sends the excess to the battery. The battery can only store DC current, so it either gets energy directly from the panels or from another inverter that changes AC back into DC.
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Using stored energy: When the sun isn’t shining, like at night or on cloudy days, your home can draw electricity from the battery instead of relying on the utility company.
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Grid backup for outages: A battery can provide backup power, keeping essential appliances running.
So how long can a battery power your home? Well, a typical battery holds 10 kWh of energy. Considering the average American household uses about 30 kWh per day, you might need to expand your battery storage to power your home for multiple days. Of course, you can ration your energy use during a blackout, too.
Another thing to consider is your solar system should be big enough to cover your energy needs plus some extra during the day so you can charge the battery. If you don’t have enough panels, you’ll end up using power from the grid to charge your battery.
Types of solar batteries
Lithium-ion and lead-acid are the two most popular types, but there are some alternative options. Here’s what you can pick from:
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Lithium-ion batteries: The most common type, offering high efficiency, long lifespan, and deep discharge capability (Tesla Powerwall, LG Chem, Enphase IQ).
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Lead-acid batteries: A more affordable option, but with a shorter lifespan and lower efficiency (used in off-grid systems).
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Flow batteries and saltwater batteries: Newer, eco-friendly alternatives with long cycle life but less widespread use.
Factors affecting solar panel efficiency
Solar panels don’t convert 100% of the sun’s energy into power, unfortunately. Many factors affect the base efficiency level and how that efficiency degrades over time. Here are a few examples.
| Factor | Description |
|---|---|
| Semiconductor material | Monocrystalline panels are more efficient than polycrystalline. Some advanced materials like gallium arsenide can achieve even better efficiency, though these are mainly used in industrial or military applications. |
| Temperature and climate | Panels perform best within a range of 59-95°F (15-35°C), though they lose efficiency with each degree over 25 Celcius. Cool and sunny climates are best for optimal efficiency. |
| Dust and debris | Panels collect dust, soot, bird droppings, leaves, and other debris over time. Bi-annual cleanings are important to minimize issues. You might notice lower output if you live in a dense city with smog, too. |
| Panel age | Solar panels typically lose between 0.3% and 0.8% efficiency per year. By the time they’re 25 years old, they’ll have about 85% to 92% efficiency. |
| Correct installation | Having a reputable company install your panels makes sure they have proper mounting, orientation, and ventilation. |
| Inverter efficiency | Some inverter types are more efficient than others. Microinverters are more efficient but they’re a bit more expensive to install. |
How to get solar panels on your home
Getting solar panels can be a lengthy process, but it’s rewarding if you know the ROI works in your favor.
Initial planning begins with calculating your household's energy consumption through detailed electricity bill analysis, which informs the optimal system capacity. Professional contractors conduct thorough roof evaluations to assess structural integrity, orientation, shading patterns, and overall solar generation potential.
The equipment package typically includes photovoltaic panels rated for residential use, sturdy mounting hardware, microinverters or string inverters, and electrical safety components.
During installation, professionals will:
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Mount support structures
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Install and connect solar panels
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Set up the inverter system
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Connect to your electrical panel
The final phase involves multiple compliance steps: securing municipal permits, passing safety inspections, establishing grid interconnection with your utility provider, and configuring real-time monitoring systems.
Homeowners should research federal, state, and local incentive programs, including solar tax credits, net metering policies, and renewable energy certificates to maximize financial benefits.
Bottom line: Are solar panels worth it?
Imagine looking at your electric bill and seeing a near-zero balance. That’s the reality for many homeowners who invest in solar panels and live in a state with net metering. But is it worth the upfront cost?
For most people, the answer is yes, but it depends on several factors:
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Your electricity costs: If your utility rates are high (like in California, New York, or Hawaii), solar panels can take a chunk out of your monthly bill.
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Sunlight availability: Homes in sunny states (Arizona, Nevada, Florida) see faster payback periods. But even in cloudy climates, solar works. Germany, a leader in solar energy, gets less sunlight than most of the U.S.
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Incentives and rebates: The federal solar tax credit (currently 30%) and state/local programs can reduce installation costs by thousands. Some areas also offer net metering, letting you earn credits for excess power.
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Home value increase: According to studies we reviewed, solar panels can increase home values by anywhere from 2% to 7%. But this increase depends on buyer attitudes, the age of the system, and the age of the roof.
There can of course be times when solar isn't the best idea, so consider your situation carefully and get the advice of an expert.
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FAQs about how solar panels work
Below are a few frequently asked questions about the inner workings of solar panels.
How does a solar panel work step by step?
Your solar panel captures sunlight and transforms it into electricity through silicon cells. Electrons jump between semiconductor layers, creating DC power. Your inverter changes this into AC power for home use.
Why is my electric bill so high when I have solar panels?
Your electric bills could still be high if your usage exceeds production (did you buy an EV?) or system efficiency drops. Also, if you have a battery, configure it to discharge so you use the power you stored at night.
Do solar panels work in winter?
Yes, your solar panels work in winter, though you’ll have reduced energy output. Cold temperatures actually boost panel efficiency, but shorter days and snow coverage mean you'll generate less power overall during winter months.
Can I run A/C from a solar panel?
You can run your air conditioning on solar panels with the right setup. An inverter will convert DC to AC so your air conditioning can use the power. You might consider battery storage if you want to run the air conditioning at night from solar power.