Solar has grown an average of 50% every year for the past decade. There’s now more than two million solar installations in the United States. It’s no wonder that more and more people are thinking of adding solar power to their homes.
Solar power isn’t new. Edmond Becquerel first demonstrated the photovoltaic effect way back in 1839. Still, how it actually works in your home to turn sunlight into electricity is a bit of a mystery to many people.
The Solar Nerd has a complete guide to solar power for your home, but if you’re looking for a quick overview, this article will explain the basic parts that make up a photovoltaic (PV) system for your house.
Solar panels are semiconductor devices that turn sunlight into electricity. The typical size of an individual panel for residential use is 65 inches by 39 inches. Each one may generate anywhere from 250 Watts to more than 350 Watts, depending on the efficiency, which can range from around 14% to more than 22%. Higher efficiency generally means higher cost, but it also means that you need fewer high efficiency panels to reach your desired total system output.
In residential systems, panels can be mounted on your roof, which is the most common application, or if you have the space for it, they can also be ground mounted.
Roof mounted systems come in a variety of types, but in all cases they are aluminum components that are bolted to your roof, onto which the panels are then secured. Flashing and sealants are used to maintain the waterproof integrity of your building.
If installed on the ground, the panels will be racked onto either aluminum scaffolding or a pole mounted rack. For an additional cost, a ground mount can include a tracking system that will automatically rotate the panels to follow the sun throughout the day, which will increase the total power generation.
If your roof ever needs servicing, the panels can be removed, but this does come with labor cost.
Photovoltaic cells produce electricity as direct current, but your house and the power grid use alternating current. It’s the role of inverters to do this conversion. Here are the types that are available:
You can read our guide to inverters to learn more.
The vast majority of home solar installations are grid-tied, which means your home will send excess power into the grid, and take power from the grid when your panels are not producing enough. Your utility will install a power meter that measures the amount of power that you draw from the grid, and the amount of excess solar power that your panels put back into the grid.
Any home PV system will provide a way for you to monitor in real-time the amount of energy that your system is producing, usually with a smartphone app or a web interface. Typical features that you’ll find are the ability to view a graph of power for the day and for selected time periods as far back as when your system was switched on.
SolarEdge is one of the major inverter vendors, and they provide a public demo account of their monitoring application that you can try.
The disconnect switch is wired between the solar panels and your electrical panel. When you pull the switch, the flow of electricity from your panels into your house and the grid is switched off. This is used when your system is undergoing maintenance, or in an emergency, such as a fire.
You should also throw the switch off during a blackout if you don’t have a system that includes a battery. A properly functioning inverter will do this automatically, but as an extra measure it’s a good idea to make sure that your panels aren’t sending electricity into the grid during a blackout. This is because unexpected electricity flowing into the grid can hurt utility workers who are performing repairs.
Due to the wide deployment of lithium-based batteries in everything from smartphones to electric vehicles, economies of scale have allowed the cost of batteries to steadily decline. Because of this, storage batteries paired with home solar is becoming more common. With a battery system, your excess solar power is used to charge the batteries. If the batteries are full, the excess will then go into the grid. At night or at times of high power usage, your home will draw power from the batteries and only use grid power when your batteries are depleted.
To be clear, batteries are not a requirement for home solar. The main application for batteries is to keep your home powered even when grid power goes down. In a grid-tied system, your inverters must synchronize the frequency of their alternating current output to match that of the grid. When the grid goes down, such as during a blackout, the inverters in a system without batteries will automatically shut down. This is also done because you are prohibited from sending power into the grid during a power failure, because it would energize power lines and potentially harm utility workers who are doing repair work.
However, if you have batteries, your house can continue to stay powered even during a blackout.
Another battery application is to have steady electricity in a home that does not have access to grid power, such as with a remote vacation home. In such a case, solar paired with batteries would allow you to run your home with solar power for most of the time, and fall back to a natural gas or diesel generator only in times of high load or during longer cloudy spells.
In spite of the benefits, the cost of a battery system is still pretty high. For example, the Tesla Powerwall is a well-known brand. Their cost estimate for a 30 kWh system that includes two Powerwalls, hardware, and installation is $14,500. Unless you are in a situation with unreliable grid power, this often doesn’t make financial sense for the typical home.
This article provides a quick overview into how solar photovoltaic systems work, but if you want to learn everything you need to make a smart decision about whether to go solar, check out our complete guide to home solar. It includes articles about the technical aspects of solar, information about how to make a smart financial decision for you, and important tips on how to find the best solar installer and compare solar quotes.