Every field has its jargon, and residential solar power and home energy is worse than most. This glossary covers the 38 terms that come up again and again in our guides and in the questions readers send us. Definitions are short on purpose: enough to unblock you, with links to deeper guides throughout the site when you want the full story.

Amperage

The measurement of electrical current flowing through a wire or circuit, measured in amps. Higher amperage means more electricity is moving through the system at any given time.

Array

A group of solar panels connected together to form a single power-generating system. Most residential solar installations consist of multiple panels arranged as one or more arrays.

Battery Storage

A rechargeable battery system that stores energy produced by your solar panels for use when the sun isn’t shining. This allows you to use solar power at night or during cloudy days.

Breaker

A safety device in your electrical panel that automatically shuts off power if too much current flows through a circuit. Breakers protect your home from electrical fires and damage.

BTU

British Thermal Unit, a measurement of heat energy that helps you understand how much cooling or heating power an air conditioner or heater provides.

Capacity

The maximum amount of energy a solar panel or battery can produce or store. Capacity is typically measured in watts for panels and kilowatt-hours for batteries.

Circuit

A complete path that electricity flows through, from a power source through devices and back to the source. Your home’s wiring contains many circuits, each with its own breaker.

Conduit

A protective tube or pipe that holds electrical wires and protects them from damage, weather, and physical contact. Solar installations use conduit to safely route wires from panels to your home.

DC Power

Direct current electricity, which flows in one direction from a battery or solar panel. Solar panels naturally produce DC power, which must be converted to AC for home use.

Degradation

The slow decrease in a solar panel’s efficiency over time, typically around 0.5 percent per year. Even after degradation, panels continue producing power for 25+ years.

Disconnect Switch

A safety device that allows you to quickly shut off power from your solar system, battery, or main electrical supply. Building codes require disconnect switches for maintenance and emergency purposes.

Efficiency

The percentage of sunlight that a solar panel converts into usable electricity. Most modern residential panels have an efficiency between 15 and 22 percent.

Electrical Panel

The main control center in your home where electricity from the grid or solar system is distributed to different circuits and appliances. It contains breakers and is typically found in a basement, garage, or utility room.

Enphase

A brand of microinverters that are installed on individual solar panels to convert DC power to AC power. This is one option for managing power in a residential solar system.

Feed-In Tariff

A payment agreement where your utility company buys extra solar power you generate and feed back to the grid. The rate paid varies by location and utility company.

Gigawatt

A unit of power equal to one billion watts. Gigawatts are typically used to measure the output of power plants or large solar installations, not individual homes.

Grid

The network of power lines and infrastructure that delivers electricity to homes and businesses. Your home remains connected to the grid even with solar panels to draw power when needed.

Grid-Tied System

A solar installation connected to the public electrical grid that allows you to draw power from the grid when your panels aren’t producing enough. Most residential solar systems are grid-tied without battery backup.

Grounding

The safety connection of electrical systems to the earth or a ground rod to prevent dangerous electrical shocks. All solar installations must be properly grounded for safety.

Inverter

A device that converts direct current (DC) power from solar panels into alternating current (AC) power that your home and appliances use. The inverter is a critical component of any solar system.

Kilowatt

A unit of power equal to 1,000 watts, used to describe the size and output of solar panels and systems. A typical residential solar panel produces about 300 to 400 watts.

Kilowatt-Hour

A measurement of energy equal to 1,000 watts used for one hour, used on electricity bills and to measure battery storage. A home using 1,000 kilowatt-hours per month uses about 33 kilowatt-hours per day.

Microinverter

A small inverter installed on each solar panel that converts DC power to AC power at the panel level. Microinverters can offer better performance when panels are in partial shade.

Net Metering

A billing arrangement where you receive credit for excess solar power you send to the grid, which offsets electricity you draw at other times. Not all areas offer net metering.

Off-Grid System

A solar installation that operates independently from the public electrical grid and relies on battery storage for power. Off-grid systems are less common in residential areas but offer complete energy independence.

Ohm

A unit of electrical resistance that measures how much a material slows down the flow of electricity. Thicker wires have lower resistance and are preferred for solar installations.

Orientation

The direction and angle at which solar panels face the sun. South-facing panels with a tilt angle matching your latitude typically produce the most energy.

Peak Sun Hours

A measure of how many hours per day the sun’s intensity is strong enough for useful solar power generation. Peak sun hours vary by location and season.

Permitting

The process of getting approval from local government authorities before installing a solar system. Permits ensure your installation meets safety codes and building regulations.

Photovoltaic

The technology that converts sunlight directly into electricity using semiconductor materials. All residential solar panels use the photovoltaic effect.

Power Factor

A measure of how efficiently electrical power is used in a circuit, expressed as a percentage. A power factor of 1.0 or 100 percent means power is being used with no waste.

Racking System

The metal framework that holds solar panels securely to your roof, ground, or pole. Racking systems must withstand wind and snow loads while allowing proper ventilation behind panels.

Rectifier

A component that converts alternating current (AC) power to direct current (DC) power. Some solar equipment uses rectifiers, though inverters are more common in residential systems.

Shading

When trees, buildings, or other objects block sunlight from reaching your solar panels, reducing their output. Even partial shading can significantly impact panel performance.

String Inverter

A single inverter that converts power from multiple panels connected in a series, called a string. String inverters are a common and cost-effective choice for residential solar.

Tilt Angle

The angle at which solar panels are positioned relative to the ground. A tilt angle equal to your latitude typically produces the most annual energy.

Voltage

The electrical pressure that pushes electricity through a circuit, measured in volts. Residential solar systems typically use higher voltages in the array and convert to standard household voltage through the inverter.

Watt

The unit of electrical power that measures how much energy is being produced or used at any moment. A solar panel rated at 400 watts produces 400 watts of power in ideal sunlight conditions.