How does solar energy work and how do we use it in our homes?
There are no moving parts. No combustion takes place, nor is any noise generated. No space is required other than the surface of your roof. It requires no fuel, just sunlight. And despite all that, it can power your entire home and produce surplus power for you to export to your neighbors.
Yes, I’m talking about solar energy. The way it works seems so remarkable and mysterious that it seems almost like magic. But solar power production is actually pretty straightforward. And, believe it or not, the solar technology used in modern solar panels has remained essentially unchanged since the 1950s.
So, how does solar energy work? What has to happen for plain ol’ sunlight to be converted into electricity that can power your home appliances?
This blog will answer those questions. It will also look at how solar energy works at night, and the role batteries play in solar power systems.
On this page:
- How solar powers your home
- How solar works at night
- Solar and battery storage
Solar panels produce clean and renewable energy without having to rely on fossil fuels.
How does solar energy power your home?
In this section, we’ll explain the process by which homes can generate and use solar energy by using solar panels.
Usable solar power is produced in 4 steps:
- Solar panels generate DC electricity
- Solar inverter converts power into usable AC electricity
- Solar inverter supplies power to the home
- Excess solar power is exported to the grid
1. Solar panels generate DC electricity
Homes with solar power systems typically have between 15 and 25 solar panels installed on their roofs.
Each solar panel comprises a string of 60 or 72 photovoltaic cells, each made out of monocrystalline or polycrystalline silicon. The solar cells are designed to capture sunlight, and convert it into direct current (DC) electricity through the photovoltaic effect.
The amount of solar electricity that is produced depends on the strength of the sunlight and the design of the solar panel. As of 2020, individual solar panels typically produce between 300 and 350 watts each under optimal conditions.
Learn more: How do solar panels work?
2. Solar inverter converts power into usable AC electricity
Home appliances are designed to use alternating current (AC) electricity, so the DC power generated by the solar cells needs to be converted before it’s supplied to the home. This function is performed by a solar inverter.
In most homes, there is a single “string” inverter installed. These string inverters, also referred to as “central inverters”, receive the combined power from all solar panels before converting it.
However, solar inverters can also be installed at the module level; in those cases, small microinverters are attached to each individual solar panel to perform the AC-to-DC conversion.
Learn more: String inverters vs microinverters
Although it often gets overshadowed by solar panels, the solar inverter (pictured) plays a crucial role in solar power production.
3. Solar inverter supplies power to the home
The inverter will then feed AC power at the required voltage (120V/240V) to your circuit board; this power is now available to service any electrical loads within your property.
With grid-tied solar power systems — the most common type of solar system installed in homes — you can, at any time, use either solar power, grid power, or a combination of both.
If the loads in your house are greater than the power supplied by the inverter, then your loads may be met by a combination of sources: partly from your rooftop solar power, and partly from the electrical grid.
Learn more: Grid-tied solar power systems
4. Excess solar power is exported to the grid
If you have solar panels installed, it’s common to generate more solar power than your total electrical loads require (what your energy needs are). When this happens, the excess energy flows out from the home to the electric grid via your utility meter.
The utility meter will need to be a special “net meter”, which can keep a separate record of what electricity you export to the grid and what you consume from the grid.
How does a solar energy system work at night?
Solar panels need sunlight to generate electricity, but we all know that the sun doesn't shine at night. To service your electrical loads after dark, a grid-tied solar panel system - the most common type of solar system - relies on power imported from your utility company.
Thankfully, there’s a good chance you won’t have to pay for much, or any, of the electricity you import at night. This is the case if you live in a state with 1:1 net metering, which is currently 38 out of 50 states. Here, the surplus power your system exported during the day is used to cancel out the cost of your electricity imports at night.
This video explains how a grid-tied solar system works by exporting energy during the day and importing energy at night.
Learn more: What is net metering and how does it work?
How does battery storage work with solar energy?
Up until now, we’ve only discussed the most popular type of solar installation in the United States, grid-connected solar systems.
You may have noticed that these systems operate without any batteries. When the grid is available, as it is for most people, the addition of batteries to a home solar energy system is optional.
Furthermore, buying solar battery storage usually doesn't make economic sense. Battery storage solutions are expensive and have relatively short lifespans, so they don’t usually pay for themselves.
That said, battery storage solutions are rising in popularity, aided by the emergence of versatile lithium-ion solutions like the Tesla Powerwall.
Here are the two common scenarios where homeowners choose to use battery solutions with their solar panel systems:
Scenario 1: Using batteries as part of an off grid system
Some people use solar energy to meet all their power needs; this is either because they’re seeking an off-grid lifestyle, or because grid connections are either unavailable or expensive to connect to (often the case in remote areas).
In such cases, homeowners pair their solar panels with battery storage to create an off-grid solar system. This allows them to store their excess daytime solar power for nighttime use.
Off-grid solar systems typically use lead-acid batteries, similar to those used in car batteries. They are the most affordable battery solution, and as such, are the preferred option when large amounts of storage are required.
Learn more: Off-grid solar: An introductory guide
Scenario 2: Using batteries for backup power
Homeowners living in blackout-prone areas are increasingly looking to battery storage as a power backup. They’re quieter and cleaner than traditional diesel generators, and don’t require going out and buying fuel.
Nowadays, most people buying batteries for backup power opt for newer lithium-ion options like the Tesla Powerwall or sonnen Eco. These batteries have a small footprint and can easily be set up to function as an independent power backup in the event of a grid outage.
However, it should be noted that battery solutions are expensive and have short lifespans, with warranties of just 5-10 years. The economics improve a bit in locations like California where you can take advantage of state battery purchase incentives and use Time of Use (TOU) rates to see some savings.
A Tesla Powerwall with Gateway hardware. The addition of the Gateway allows you to use the Tesla Powerwall as a backup power supply. Image source: Electrek
Make solar power work for your home
The process of going solar can appear complicated first. But with the right resources, you can get a solar panel system up and running on your roof within a matter of weeks.
The first challenge is to understand how solar technology works. The fact that you’re reading this blog means that you’re well on your way to tackling this task.
The next step in your solar journey is potentially even trickier: figuring out if solar power is right for you. The good news is that SolarReviews has all the tools and information you need to achieve that task.
Our solar calculator will provide you an advanced solar estimate for your home. It draws on location-based data, satellite imagery and machine learning to tell you how many solar panels you need, how much it will cost you, and how much money you will save. In other words, our calculator shows you all the information you need in order to decide if getting solar panels for your home is worth it.
There’s just one more major step after that: choosing the best brands of solar equipment, and the right solar company to install them for you. Here, again, SolarReviews can help. We have a huge database of solar equipment brands and solar installation companies on our site. Be sure to read product information, consumer reviews, and rankings in order to make the right choices.
Once the solar panels are installed, you’re all set. Solar panels are designed to last a minimum of 25 years, and require minimal maintenance. You can then sit back and enjoy the clean energy you’re producing — and all the financial savings you’ll realize in the process.
- Solar panels convert sunlight into electricity using the photovoltaic effect.
- A solar inverter converts the electricity into AC electricity and sends it to the home’s circuit board.
- Excess solar power is exported to the grid; in return, you can receive credits that cancel out the power you import at night.
- The addition of battery storage is optional, but is commonly used in off-grid homes and as a source of backup power.
If you want to learn more about solar energy, including how it compares with other energy sources, check out this beginner’s guide to solar power.
Author: Andrew Sendy | Home Solar Journalist
Andy is deeply concerned about climate change but is also concerned about cost of living pressures on American families. He advocates for solar energy and solar battery storage only to the extent that they make financial sense for homeowners. He is not affiliated with any particular solar company in the United States.