Glossary of Terms

A passing familiarity with these terms will help you communicate with your solar installer.

Alternating Current (AC): Alternating current (AC) is a type of electric current that alternates in direction. AC electricity is the type of electricity used in homes and businesses, and it is produced by an inverter in a solar panel system.

Direct Current (DC): Direct current (DC) is a type of electric current that flows in one direction. Solar panels generate DC electricity, which is not compatible with the alternating current (AC) electricity used in homes and businesses.

Grid-Tied: A grid-tied solar panel system is connected to the electrical grid and is able to sell excess solar energy back to the grid. Grid-tied systems are typically more cost-effective than off-grid systems, as they do not require the use of batteries to store excess solar energy.

kW vs kWh: kW stands for kilowatts, and it is a unit of power. One kW equals 1,000 Watts. One megawatt equals 1,000 kilowatts. For example, ten 400 Watt panels would be referred to as a 4 kW system. kWh stands for kilowatt-hours, and it is a unit of energy, (power over time). One kWh equals on kW used for one hour.

Main Service Panel (MSP): The main service panel, also known as the breaker box or electrical panel, is the central hub of a home's electrical system. It is responsible for distributing electricity throughout the home and protecting the electrical circuit from overload. The main service panel is typically located in a central location in the home, such as a utility room or basement, and it contains circuit breakers or fuses that control the flow of electricity to different areas of the home.  Alternating current (AC)  generated by the solar inverter is fed into the electrical system at the MSP. A disconnect switch allows the solar panel system to be safely disconnected from the electrical grid in the event of an emergency or maintenance. Sometimes, a home's MSP may need to be upgraded to accommodate the additional electrical load from a solar panel system.

Microinverter: A microinverter is a small inverter that is connected to an individual solar panel and is responsible for converting the direct current (DC) electricity from just that one panel into alternating current (AC) electricity. This means that each solar panel has its own microinverter, and the AC electricity from each panel is fed directly into the electrical panel.

Net Billing: Net billing is a policy that allows homeowners with solar panel systems to sell excess solar energy back to the grid at a predetermined rate. This is different from net metering, which credits excess solar energy at the same rate as the energy being consumed.

Net Metering: Net metering is a policy that credits excess solar energy at the same rate as the energy being consumed. This means that if a homeowner generates excess solar energy, they receive a credit on their energy bill for the excess energy at the same rate as the energy they purchase from the grid.

Off-Grid: An off-grid solar panel system is not connected to the electrical grid and is not able to sell excess solar energy back to the grid. Off-grid systems typically require the use of batteries to store excess solar energy for use when the sun is not shining.

Permission to Operate (PTO): Permission to operate (PTO) is a document that grants a homeowner or business permission to install and operate a solar panel system. PTOs may be required by state or local regulations, and they typically outline any rules or restrictions that must be followed in the operation of the solar panel system.

Power Optimizer: A power optimizer is a device that is connected to individual solar panels and is designed to optimize the performance of the panel. Power optimizers can help improve the efficiency of a solar panel system by optimizing the voltage and current of the panels and minimizing losses due to shading or other factors.

Solar Access: Solar access refers to the ability of a property to receive sunlight, which is necessary for solar panel systems to generate electricity. Factors that can affect solar access include shading from trees or buildings, the orientation of the property, and local zoning laws.

String Inverter: A string inverter is an inverter that is connected to multiple solar panels, and is responsible for converting the direct current (DC) electricity from all of the connected solar panels into alternating current (AC) electricity. String inverters are typically located near the electrical panel or breaker box in a home, and the AC electricity is fed into the electrical panel and used by the home.

Watts: Watts are a unit of power. In the context of solar panel systems, Watts refer to the rate at which energy is being generated or consumed. Always capitalized, as it is named in honor of James Watt.