One of the most common criticisms lobbed at those who believe that solar power is key to helping the world transition to renewable energy is that solar panels only work for half the day. After all, they are called "solar" panels, so what happens when the sun sinks below the horizon? Do solar panels simply stop working, leaving solar panel owners literally in the dark? In this article, we’ll tackle this criticism head-on. We’ll review how solar panels work, what happens to solar panels on cloudy days and at night, and how solar panels can still help power the world whether the sun is shining or not.
Do solar panels generate power at night? The simple answer is “no.” To understand why we first need to look at how solar panels work. Get ready; we’re about to get sciency!
The sun produces massive amounts of energy that it sends to Earth in the form of photons. Solar panels are made up of lots of little photovoltaic cells, usually sandwiched between two slabs of silicon. (This is why solar panels are often referred to as photovoltaic or PV panels.) When photons hit the photovoltaic cells, they knock electrons loose from their atom. The two slabs of silicon each have a different charge, which creates an electric field. This electric field forces the wayward electron to scurry through a circuit. It’s this movement of electrons that creates a direct current (DC) that is then converted into the alternating current (AC) that powers your appliances, light bulbs, and all other electronics.
Without photons from the sun to knock them loose, the electrons within a solar cell stay snug in their orbits around an atom and don’t create power. For this reason, solar panels essentially do not create power or “work” during the night. (Nope, the moon doesn’t send down its own photons. It’s not a star like the sun.)
Does this mean that solar panels can’t provide enough energy for homeowners and will cause them to lose power at night? Absolutely not.
Before we explain why, let’s look at another common and related question:
Solar panels don’t work at night, but does that mean that they are equally useless during cloudy days? Many homeowners who live in more overcast parts of the state ask us this question, worried that solar panels won’t be a good option for them.
We are happy to report that solar panels DO function during cloudy days. Just as clouds don’t block all of the sunlight on a cloudy day, they also can’t stop all of the sun’s photons from hitting the earth and your solar panels. (This is also why you can still get sunburned on a cloudy day and should wear sunscreen even when the sky is overcast!)
Cloudy days do affect solar panel efficiency. Less sun equals less energy creation. Depending on how overcast the sky is, a cloudy day can reduce solar panels to 25% to 10% of their normal efficiency. This is a pretty big drop in efficiency, but the key detail is that solar panels can operate in cloudy conditions.
Homeowners who live in cloudier parts of California, especially in areas of the state with higher-than-average energy costs, can still benefit from investing in solar panel systems. Their systems will have to be larger than the systems of a similar home in a sunnier part of the state in order to produce the same amount of energy. Still, solar panels can be a good deal for these homeowners, helping them to save on their energy bills. Most importantly, these systems will still pay for themselves over time. Even in the cloudiest parts of the state, a solar system will typically pay for itself in six to nine years!
(Check out our previous blog post all about how weather affects solar panel.)
Wait, what? Didn’t we just explain that solar panels don’t produce energy at night? True, but that doesn’t mean solar panels can’t power your home after the sun goes down. In fact, there are two different ways your solar panels can generate enough power to cover your energy needs day and night.
The first method is through California’s net metering system. The second option is to take advantage of the improving slate of solar batteries on the market.
California has a net metering system, which allows homeowners with solar panels to send excess energy back into the energy grid in exchange for energy credits. (Your energy meter will actually tick backwards!) When homeowners need more power than their solar panels produce, they can then take energy back out of the grid, causing their energy meter to tick forward.
Ideally, your solar panel installer will help you determine your home’s average monthly energy use and then recommend a system size that produces that equivalent of power. (Learn about how to figure out how many solar panels you need for your home.) This doesn’t mean that your system will produce the same amount of power each day, each week, or even each month. For example, during the long days of summer, your system will likely produce an excess of power, which will allow you to stockpile credits. During the shorter winter days, you’ll use those credits as you pull energy from the grid. If your system is designed correctly, everything should balance out by the end of the year, helping you realize big energy savings.
In this way, your public utility acts as a sort of storage system for your solar power. During the day when your panels are producing their maximum amount of power, your family members may be at work or school and not be using a lot of power at home. Your system will pump that excess power into the grid to build up your credits. At night, when you need to turn on more lights, or when you want to put on the air conditioning to cool the house down before bed, you’ll use your credits and pull energy back out of the grid.
Net metering is one of the reasons that solar technology has been so successful in California and why it quickly helps homeowners recoup their solar panel investment.
Rather than relying on a public utility to store your excess power until you need it at night, you could always store the power your solar panels create during the day yourself with the help of a solar battery. Over the past few years, we’ve seen a new generation of residential solar batteries hit the market like Tesla Powerwall. These batteries are much more powerful than their previous iterations and can hold significantly more power for a longer period of time.
Solar batteries can be a great solution is you don’t receive service from a public utility provider, or if you want to live off the grid as much as possible. Of course, relying on a battery does require a more focused approach to your energy usage. You’ll have to keep a close eye on your battery’s charge and how much energy you use. Additionally, short winter days or a week of overcast weather could make it difficult for your solar panels to create all the power you need even with a battery.
Still, the technology behind solar batteries only continues to improve, and as the economies of scale increase, prices for solar batteries like Tesla Powerwall will begin to drop, just as they have for solar panels.
Do solar panels work at night? No. But the idea that they can’t help Californians dramatically lower their energy costs or be part of the solution to transition from dirty fossil fuels to clean renewable energy is false. Solar power is one of the main driving forces helping California reach its 2030 goal to generate half of its power from renewable energy. In fact, Californians have embraced solar so much that a 2017 report from the California Public Utilities Commission found that the Golden State may hit this “ambitious” goal a decade early!
California’s net metering system, as well as the recent improvements in solar battery technology, have allowed homeowners to power their home day and night with a solar panel system on their roof.
Are you interested in learning more about solar panels for your home? At Semper Solaris, we have established offices throughout California. Our solar representatives can help you determine how much power your home requires on an average monthly basis, which will let us recommend the ideal solar panel system for your energy needs and budget. We also offer solar batteries and can install your solar panel system and your solar battery together if you would prefer to live off the grid.
If you want to take advantage of California’s net metering system, we will work with your local public utility to have your system permitted, reviewed, approved, and connected to your local utility provider.
Contact us today to schedule a free, no-obligation energy audit of your home.
