Solar panels have taken the world by storm over the last decade, and their popularity doesn't seem to be slowing down anytime soon. As of January 2019, the US has more than 1.9 million solar installations. It's expected to cross 2 million by early 2019, and be double that by 2023.
Although these systems aren't new, many people still haven’t figured out how exactly the technology works. How do solar panels produce electricity? Do solar panels work in cloudy weather? What about after dark — do solar panels work at night?
We answer these questions and more below. Let's take a look!
What are solar panels?
Let’s start at the beginning. Solar panels are made up of several smaller units known as solar cells. The devices work by gathering light provided by our neighborhood star, the sun. They then convert the light into direct current (DC). You may hear the power they produced referred to as photovoltaic (PV) energy; this translates to ‘light-electricity.’ A single panel will just generate electricity sufficient for 1 or 2 smaller appliances. To create a solar system that can power a house or building, you would require an array with many solar panels connected together.
How do solar panels work?
Here’s a more technical and detailed explanation of how these devices work:
As the solar panels convert light into power (DC), the power gets sent through the system's inverter. From there, it gets converted to alternating current (AC) power. Is this ringing a bell from science class? If not, we'll remind you. AC is the power most households run on. This is what you get when the utility feeds electricity into your home for you to watch television, cook dinner, and simply turn on the lights.
Any energy produced by your system that you don’t use gets sent into battery storage or the electric grid; we'll touch on this a bit later. Solar systems work best when the most light hits the cells. This produces the most electricity. This begs the question: what happens on an overcast day?
Do solar panels work in cloudy weather?
Yes, solar panels do work on cloudy days — but not as effectively as they would on a sunny day. Expect them to produce 10-25% of their normal power output, depending on how thick the cloud cover is. But there’s an interesting twist: although they work better on sunny versus cloudy days, solar panels don't work best in particularly hot climates. In fact, solar panel output begins to fall if the temperature rises above 77 degrees Fahrenheit (25 degrees Celsius).
Because of this, solar panels work better in certain areas than others. For example, even though Las Vegas has sunnier and hotter days, solar panels tend to generate more power than in San Francisco. SF’s cooler weather keeps the device at an optimum temperature for energy output when the sun is shining.
You might also be surprised to know that solar systems are popular in many famously overcast places, such as in the city with the most cloudy days in America, Seattle. The second cloudiest city, Portland, Oregon actually ranks among the top cities for solar power in the US. Both cities benefit from long summer days with mild temperatures — ideal conditions for maximum solar production — which helps balance out lower production in the cloudy winter months. In summary: on cloudy days solar panels do work; just less effectively. But solar panel performance also drops when it is too hot. That being said, solar panels can work and be worth it across a range of different climates.
Do solar panels work at night?
The answer is no, they don’t. As we mentioned earlier, solar panels need light — preferably sunlight — to create energy. Although they can generate some energy from other light sources such as street lights and even the moon, the output is very low. Because of this, solar panels go into sleep mode at night, i.e. they become inactive and stop producing electricity.
Then how do homes with solar panels have power at night?
As mentioned above, solar panels produce no electricity at night. But they tend to produce extra power during the day when the sun is out. In order to balance things out, and keep the electricity running after dark, solar customers use either solar battery banks to store energy or net metering.
Solar battery storage
The concept behind solar energy storage is simple. Most solar systems are intentionally designed to produce more power than your home needs during the daytime. The surplus power generated during the day is stored in a solar battery solution such as the Tesla Powerwall 2.
At night, when your solar panels are in sleep mode, you can use the stored energy held by the battery system to power your home. Some houses with his setup are even able to operate off grid, i.e completely independent of the utility;
Net metering which is like using the grid for storage
If your solar panel system doesn't have storage, you can still use your surplus solar energy at night. How? Through net metering! With net metering, you don’t have physical energy storage at your home. Instead, the excess power your solar panels produce during the day is exported to the utility grid. You receive credits for this power, which accumulate in your account.
Later, at night — or any other time you use power from the grid — you can use your credits to offset the cost of the energy. In other words, net metering lets you store the economic value of the excess power you produce, which you can use to reduce or even completely cancel out your electric bills. Net metering makes solar power a very good deal. Read more: What is net metering and how much does it get me for exported solar?
Recap: when do solar panels work
To summarize, your solar panel system will work on cloudy days and actually works better when it’s not too hot. How efficient your panels are under different weather conditions will depend on your solar panel brand; so make sure to check out SolarReviews for more information about brands and/or talk to a solar company to see how many solar panels you need.
We hope this has answered your question! If you have more or are wondering if solar panels are worth the investment, make sure to check out our website.
And if you want to know if solar panels are worth it for your house, enter your zip code below. You will receive an estimate that shows you how much solar panels will cost for your home, and how much you can save each month.