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How Does Solar Power Work, Anyway?

Renewable Energy
Portland General Electric

You've seen the panels. And now you know about solar's incredible potential. Which means you probably have some questions. So let's get to it.


How do solar panels work?

A solar panel "works by allowing photons, or particles of light, to knock electrons free from atoms, generating a flow of electricity," according to Live Science. That's a technical way of saying that the panel's photovoltaic cells convert the energy in sunlight to electricity (specifically, direct current (DC)). This DC electricity is then converted to alternating current (AC) by an inverter.

AC is the type of electrical current you typically use when you plug anything into a residential wall socket. If you have solar on your roof, the system's electrical panel sends power to your lights and appliances.

How long will solar panels last?

A long time. Like, a really long time.

Many home array solar panels are guaranteed for decades, thanks to warranties that typically cover 25-30 years. But because their parts do not wear out easily, solar arrays are well-known to continue producing clean electricity even beyond these lengthy timeframes.

"Unlike many other consumer goods, [solar panels] don't 'give up the ghost' at the end of their warranty period and need to be replaced, but continue to still produce clean electricity, although at a slightly less efficiency each year," Clean Technica reported.

"In fact, some decidedly old-school solar cells have been producing electricity daily for about 40 years or so, and are expected to continue to power homes and businesses for decades more."

A June 2012 NREL study investigating the "photovoltaic degradation" rates of about 2,000 solar installations over a period of 40 years found the median solar system lost just 0.5 percent of its efficiency per year. So, by the end of your 25-year warranty, the solar panels on your roof could still be operating at about 88 percent of their original capacity.

Is your '93 Camry still running near-perfect with very, very little maintenance (more on that below)?

(Psst … a quick note on the word "photovoltaic": It means "capable of producing a voltage, usually through photoemission, when exposed to radiant energy, especially light." Which is a very long way of saying "converts sunlight into electricity.")

What sort of maintenance is required?

Not too much, really. Your solar panels themselves can last for decades on end without much upkeep (maybe just remember to keep them free of debris, snow, etc.). But you will likely need to replace the inverter a few times throughout the life of your system.

Like the solar panels themselves, inverters typically come with a warranty—these can range from 5-15 years (and sometimes even longer). Unlike your panels, your inverter will not see its efficiency dwindle very slowly; instead, it may simply stop working and need to be replaced.

However, technological developments on this front are afoot! New "micro-inverters," which are installed or included with each solar panel, are quickly replacing the more-common central inverters that handle the output of all your panels at once. These micro-inverters can have a much longer lifespan (all the way up to 25 years) than a central inverter, and if one does fail, it won't shut your entire system down cold.

Do solar panels work on cloudy, rainy, or cold days?

We'll cut straight to the chase—solar panels work just fine when it's cloudy, rainy, and/or cold.

Are clouds and rain ideal for solar panels? Of course not. They are most effective in direct sunlight. But solar panels can still generate power when the sun is blocked by clouds—more than enough, in fact, to remain a viable source of electricity. Take Germany, for example. It's not particularly warm or sunny, but is nevertheless a world leader in solar energy.

As for winter, there's some even better news: Solar panels are powered by light, not heat, and because of the way the technology works, they're just as effective—if not more effective—in cooler temperatures as in hot ones.

How much does a solar energy system cost?

That depends.

"In 2018, most U.S. homeowners are paying between $2.71 and $3.57 per watt to install solar, and the average gross cost of solar panels before tax credits is $18,840," EnergySage estimated.

That may seem quite expensive, but it also doesn't take into account the many incentives available to solar customers and the multiple new forms of solar financing that have emerged in recent years that can allow customers to put solar on their rooftops at little or no cost up front.

In addition, in the U.S., a 30 percent federal investment tax credit is available until 2019 (stepping down in the years beyond) and can offset the cost of your investment substantially, and many states also offer their own tax breaks and incentives to encourage home solar panel installation.

And, of course, looking at the straight upfront cost of the system and its installation is far from the whole story, at least as far as your bank account is concerned. Which leads us to our next question …

Can people really save money with solar panels?

Yes. Not only does a solar energy system add substantial value to your home the minute it's up and running, it often pays for itself—and then some!

"Twenty-year electricity savings from solar can be significant, ranging from the low end of $10k to almost $30k," according to EnergySage.

If you follow that math—and please keep in mind your savings will vary, depending on factors like your typical electricity cost, average sunlight in your region, and the scale of your system you install—depending on the final cost of your system after federal, state, and local incentives, in as little as seven-and-a-half years, your system will have paid for itself.

Few major purchases can claim such an impressive return on investment.

Looking at these numbers, the conclusion is clear: Solar isn't just the right choice for the planet—it can also be the smart choice for your wallet. Whatever fossil fuel companies may claim.

The benefits of solar don't end with lower power bills. Cutting carbon pollution? Check. Empowering communities? Check. Creating good jobs? Check and check.

And all that's before we even get to solar's part in transitioning to a clean energy economy and avoiding some of the worst possibilities of climate change. Like increasing extreme weather and the terrible—and terribly expensive—destruction that can come with it.

Learn more about the benefits of renewable energies like solar by downloading our free new fact sheet, Climate 101: What Is Renewable Energy?

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