Solar Glossary

The type of electrical current used in homes and businesses. Solar panels produce DC power, which inverters convert to AC for home use.

The compass direction that solar panels face, measured in degrees from north. In the Northern Hemisphere, south-facing (180°) is typically optimal.

All solar system components except the panels themselves—including inverters, racking, wiring, and monitoring equipment.

Rechargeable batteries (like Tesla Powerwall or Enphase) that store excess solar energy for use at night or during outages.

Solar panels that capture sunlight on both sides, generating additional power from light reflected off the ground or roof.

The ratio of actual energy produced to maximum possible energy if panels ran at full capacity 24/7. Typically 15-25% for residential solar.

When solar panels produce more DC power than the inverter can convert to AC, causing some energy to be "clipped" or lost.

Solar installations on businesses, warehouses, or commercial buildings, typically larger than residential systems.

The type of electrical current produced by solar panels. Must be converted to AC by an inverter before use in your home.

The gradual decrease in solar panel output over time, typically 0.5% per year. Quality panels maintain 80%+ output after 25 years.

A utility fee based on your highest power usage during a billing period, common for commercial accounts.

A company that handles the complete solar installation process from design through construction.

An assessment of your home's energy use to identify efficiency improvements and right-size your solar system.

A policy where utilities pay solar owners a set rate for electricity fed into the grid. Less common in the US than net metering.

Solar panels mounted at a permanent angle, as opposed to tracking systems that follow the sun.

A solar system connected to the utility grid, allowing you to draw power when needed and export excess production.

Solar panels installed on a ground-based racking system instead of on a roof. Useful for homes with unsuitable roofs.

An inverter that works with both solar panels and battery storage, managing power flow between all sources.

The process of connecting your solar system to the utility grid, including permits and utility approval.

Device that converts DC electricity from solar panels to AC electricity for home use. Types include string inverters and microinverters.

Federal tax credit for solar installations. As of 2026, the 30% residential credit (25D) expired for purchases; 30% still available through PPA/lease (48E) until 2027.

The amount of solar radiation hitting a surface, measured in watts per square meter (W/m²). Higher irradiance = more solar production.

A unit of power equal to 1,000 watts. Solar system size is measured in kW—the average home system is 6-10 kW.

A unit of energy equal to using 1,000 watts for one hour. Your electric bill measures usage in kWh.

The pattern of your electricity usage throughout the day. Important for sizing systems and evaluating time-of-use rates.

Tax depreciation benefit for commercial solar installations, allowing accelerated write-off of system costs.

A small inverter attached to each individual solar panel, converting DC to AC at the panel level. Better for shaded roofs.

Another term for a solar panel—the individual unit containing photovoltaic cells that generates electricity.

Solar cells made from a single silicon crystal. More efficient (19-23%) and more expensive than polycrystalline.

Technology in inverters that optimizes power output by continuously adjusting to find the ideal voltage.

Policy allowing solar owners to receive credit for excess electricity sent to the grid. Also called net metering.

A billing arrangement where excess solar energy sent to the grid earns credits that offset electricity drawn from the grid later.

Similar to net metering, but excess solar is credited at a lower wholesale rate instead of full retail rate.

A solar system not connected to the utility grid, relying entirely on solar and batteries. Requires significant battery storage.

A device attached to each panel that optimizes DC output before sending to a central string inverter. Middle ground between string and micro.

The time it takes for electricity savings to equal the cost of your solar system. Typically 6-12 years depending on location.

Hours per day when sunlight intensity equals 1,000 W/m². Used to estimate solar production—US averages 4-6 peak sun hours.

Government approval required before solar installation. Includes building permits and sometimes electrical permits.

Technology that converts sunlight directly into electricity using semiconductor materials like silicon.

Solar cells made from multiple silicon crystals. Less efficient (15-17%) but cheaper than monocrystalline.

A financing arrangement where a third party owns the solar system on your roof, and you buy the electricity it produces at a set rate.

A warranty promise that your system will produce a minimum amount of energy, with compensation if it falls short.

Final approval from your utility allowing you to turn on your solar system and connect to the grid.

The mounting system that secures solar panels to your roof or ground mount structure.

Safety requirement that solar systems can quickly de-energize to protect firefighters. Required by electrical code since 2017.

The financial return from your solar investment, calculated as total savings divided by system cost.

Using solar energy directly as it's produced, rather than exporting to the grid. Maximizes value in areas with low net metering rates.

Assessment of how trees, buildings, or other obstructions affect sunlight on your roof throughout the year.

A financing arrangement where you rent solar panels for a fixed monthly payment. The leasing company owns and maintains the system.

A loan specifically for financing solar installations, allowing you to own the system while paying over time.

A tradeable certificate representing 1 MWh of solar electricity generated. Some states require utilities to buy SRECs, creating income for solar owners.

A central inverter that converts DC power from multiple panels wired together in "strings." Most common and cost-effective type.

The angle at which solar panels are mounted relative to horizontal. Optimal tilt roughly equals your latitude.

Electricity pricing that varies by time of day—higher during peak demand periods, lower overnight. Affects solar economics.

A mounting system that moves panels to follow the sun throughout the day, increasing production by 25-35%. Mostly used in utility-scale solar.

Large solar installations (typically 1+ MW) that sell electricity directly to utilities or the wholesale market.

The basic unit of electrical power. Solar panel output is measured in watts—residential panels typically produce 350-450 watts each.

The maximum output of a solar panel under standard test conditions (1,000 W/m² sunlight, 25°C temperature).