A solar array is the complete power-generating unit made up of multiple solar panels wired together. It’s the full collection of panels you see on a rooftop or in a field, working as one system to produce electricity from sunlight. While people often use “solar panel” and “solar array” interchangeably, they refer to different levels of the same technology.
Cells, Panels, and Arrays
Solar technology has a simple hierarchy. At the smallest level, you have a photovoltaic cell, a single piece of semiconductor material (usually silicon) that converts light into electricity. Dozens of these cells are wired together and sealed behind glass to form a solar module, commonly called a solar panel. That panel is what you’d buy as a single unit at a hardware store or from an installer.
A solar array is any number of these panels connected together. A small residential array might be 15 to 20 panels on a roof. A utility-scale solar farm can contain hundreds of thousands of panels spread across acres of land. Regardless of size, the term “array” refers to the whole system working as one power-generating unit.
How Solar Arrays Generate Electricity
Sunlight is made of photons, tiny packets of energy. When photons hit a solar cell, most are absorbed by the semiconductor material inside. That absorbed energy knocks electrons loose from their atoms. The cell’s surface is specially treated during manufacturing so these freed electrons naturally migrate toward the front of the cell, creating a voltage difference between the front and back, similar to the positive and negative ends of a battery.
Metal conductors on the cell capture those electrons. When connected in a circuit, the electrons flow as electricity. Solar cells produce direct current (DC), the same type of power a battery provides. Since homes and the electrical grid run on alternating current (AC), the array needs an inverter to convert the power before it can be used.
How Panels Are Wired Together
The way panels are connected within an array determines how much voltage and current the system produces. There are two basic configurations: series and parallel.
In a series connection, you link the positive terminal of one panel to the negative terminal of the next, like batteries in a flashlight. This adds the voltages together while the current stays the same. Three panels rated at 18 volts and 6 amps wired in series produce 54 volts at 6 amps.
In a parallel connection, all the positive terminals connect together and all the negative terminals connect together. This adds the currents while voltage stays the same. Those same three panels wired in parallel produce 18 volts at 18 amps.
Most residential and commercial arrays use a combination of both, called a series-parallel configuration. A group of panels wired in series forms a “string,” and multiple strings are wired in parallel to each other. This lets installers dial in the right balance of voltage and current to match the inverter and maximize output. For example, two strings of two 18-volt, 6-amp panels would produce 36 volts and 12 amps, roughly 432 watts.
Inverters and Power Conversion
The inverter is the piece of equipment that makes the array’s electricity usable. There are two common approaches, and they affect how well the array performs.
A string inverter is a single box, usually mounted on a wall near the electrical panel, that handles the conversion for an entire string of panels. It’s less expensive, but it has a weakness: if one panel in the string is shaded or underperforming, it drags down the output of every panel in that string.
Microinverters are small units attached to each individual panel. Every panel converts its own power independently, so shade on one panel doesn’t affect the others. Research comparing the two technologies has confirmed that microinverter systems produce more energy in both shaded and unshaded conditions. The trade-off is higher upfront cost, though the increased energy production can offset the difference over time.
Efficiency and Degradation
Not all the sunlight hitting a panel gets converted to electricity. In 2025, standard residential panels typically achieve 21% to 22% efficiency, with top-performing models reaching 23% or higher. Nearly all home installations use monocrystalline panels, which are the most efficient type available for residential use. Polycrystalline and thin-film panels exist but are less common on rooftops.
Solar arrays do lose a small amount of output over time as the cells degrade. The conventional estimate was a 0.5% loss per year, but a large study of 53 solar plants over roughly a decade found the actual degradation rate was lower, between 0% and 0.29% annually. At that rate, an array retains the vast majority of its original output even after 25 or 30 years of operation. Most manufacturers back this up with production warranties lasting 25 years or more.
Roof-Mounted vs. Ground-Mounted Arrays
Roof-mounted arrays are the most common residential option and typically cost less to install than ground systems. The panels sit on brackets attached to your roof, keeping your yard space free and making them harder for anyone to tamper with. The downsides: shingle roofs require penetrations for mounting hardware, and if your roof needs replacement down the road, the panels have to come off and go back on. You’re also locked into whatever direction your roof faces and whatever angle it sits at, which may not be ideal for solar production.
Ground-mounted arrays can be positioned to face any direction at any angle, so they’re often optimized for maximum energy production. They’re easier to access for maintenance and cleaning. But they cost more to install, take up yard or land space, and typically require fencing. They’re a strong option when your roof is too old, too small, heavily shaded, or facing the wrong direction. Commercial properties sometimes use carport-style ground mounts over parking lots, which provide shade for vehicles while generating power.
System Size and Cost
Most homes need a solar array rated between 5 and 10 kilowatts to cover their electricity usage. A 5 kW system might consist of about 12 to 15 panels, while a 10 kW system could require 24 to 30, depending on the wattage of each panel. Your actual size depends on your electricity consumption, roof space, local sunlight, and how much of your bill you want to offset.
The national average cost for residential solar is about $3.03 per watt before incentives, putting a typical system somewhere between $15,000 and $30,000 before the federal tax credit. Financing through a solar loan raises the effective cost to around $3.62 per watt when interest is factored in. Commercial installations are cheaper per watt, averaging about $2.00, because larger systems benefit from economies of scale. The federal solar tax credit, currently at 30%, brings the out-of-pocket cost down significantly for both residential and commercial installations.