Home Solar Glossary

There are a lot of terms specific to the home solar industry. Some are confusing and others may just be new to your vocabulary. Below, you’ll find the definitions for several commonly used solar technology terms to help make things more clear.

Solar panels: Also called solar modules, solar panels are made up of silicon cells that absorb sunlight to create a photovoltaic (PV) effect that allows for the conversion of sunlight to electricity.

Solar Strings and Solar Arrays: Individual solar panels are linked together to form a string of panels, also known as a solar string. A solar array can be made of one or more solar strings. The solar array is then connected to an inverter to make electricity for your home.

Solar inverter: The inverter is the electrical box that turns the direct current (DC) electricity produced by the solar panels into the alternating current (AC) electricity used by the utility grid and your household appliances.

Balance of System (BOS): The Balance of System (BOS) includes rails or racking for the solar panels, roof integration equipment, and wiring and conduit.

Solar panels in a solar array plus the solar inverter plus BOS make up a residential solar system.

The Grid: The grid is a network of cables that carries and transmits electricity from large centralized power plants to individual homes. The term “going off the grid” applies when a household generates all of its own power and no longer has to rely on drawing electricity from the grid.

Utility: Depending on where you live, you get your power from a local municipality or from a large power-producer, like PG&E or SMUD for example. Utilities produce power and send it to you via the grid. In cooperation with state and federal laws, utilities must compensate you once you install solar and start generating your own electricity.

Net Metering: When you install a solar system, your utility monitors how much electricity your solar panels produce and how much electricity you use through a process known as net metering. If your home solar system generates more electricity than you use, you export it to the grid and receive credit from your utility. When you use more electricity than you generate, like at night, you draw it back off the grid as required. Your utility determines the difference between the electricity you generate and what you use from the grid, and bills you for that difference.

Module Power Ratings: To help standardize measurement of a solar panel’s power output, several government rating agencies created power rating standards. The most common ratings are STC-DC and CEC-AC.

It’s a little confusing because both ratings are widely used, often together, and each measures the solar panel output in a slightly different way.

• STC-DC (Standard Test Condition Direct Current) rating measures a panel’s output in ideal laboratory test conditions. It is the standard global power rating for solar panels.
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• CEC-AC (California Energy Commission Alternating Current) rating measures a panel’s output in real life production conditions and factors in the inverter’s efficiency of converting DC to AC. The CEC-AC is always lower than the STC-DC rating, because it takes in to account the inefficiencies in the rest of the solar system.
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You may see both the STC-DC and CEC-AC ratings next to the size of a solar system, for example in a quote:

2.4 STC-DC System Size
2.12 CEC-AC System Size

We found the differences with these ratings to cause unnecessary confusion, so we refer to our systems by name: A, B, C, D and E (A being our smallest system). To allow comparison with other quotes, we will still include cost per kWh (STC-DC & CEC-AC) in the quote we provide you.  We also use the industry ratings behind the scenes to calculate the total energy output of your system.

Ultimately, what matters to you - the investor in a home solar system - is the amount of annual energy generated (and saved), the environmental benefits, and the financial returns, so we stick to those details.

Call us at 877.257.8648 or enter your address at the top of the page for your free solar estimate today!