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 photons (sunlight) to create a photovoltaic (PV) effect that allows for the conversion of sunlight to electricity. (Silicon just happens to be the Earth’s most abundant element other than oxygen and is used to make computer chips, glass, cement and solar panels.) Solar panels are linked together to form "strings" and strings are combined to form "arrays". This array is connected to your home via an inverter, delivering electricity to power your home or back to the grid, if your system produces more electricity than you use.
Solar Inverter
The solar inverter is the electrical box that turns direct current (DC) electricity produced by the solar panels into alternating current (AC) electricity. A grid-tied solar inverter allows this AC electricity to be sent back to the grid when you produce more energy than you use. Check out our video on how an inverter works.
Balance of System
The Balance of System includes racking for the solar panels, roof integration equipment, wiring, and conduit. Just add panels and an inverter and you've got a home solar system!
The Grid
The grid is a network of powerlines that carries and transmits electricity from large centralized power plants to individual homes. The term “going off the grid” refers to a household that generates all of its own power and no longer has to rely on the grid. Sungevity systems are "grid-tied" (or connected to the grid) so that you can still power your house when the sun doesn't shine and can take advantage of all the tax incentives, as well as state and municipal rebates that are available for grid-tied systems.
Utility
Depending on where you live, you get your power from a local municipality (e.g., SMUD: Sacramento Municipal Utility District) or from a large power-producer (e.g., PG&E: Pacific Gas & Electric Company). Utilities produce power and send it to you via the grid.
Net Metering
When you install a grid-tied 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. Because the amount of power you'll generate is greater during the summer than in the winter, this balance is reconciled at the end of each year.
If, at the end of the year, you have produced more than you used some utilities will compensate your for this extra power but others will not. Contact your utility for up-to-date information about their Net Metering or Solar Bank program.
Batteries
Batteries aren't needed with a grid-tied system as the grid itself serves the purpose of providing electricity when your rooftop solar isn't producing power. All those credits you accumulate when the sun is shining help pay down or completely negate the cost of electricity you utilize at night or on a cloudy day!
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 and is the standard global power rating for solar panels. CEC-AC (California Energy Commission Alternating Current) rating measures 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 account of inefficiencies throughout the balance of the solar system.
Solar Lease
A Solar Lease is a legal agreement between you and Sungevity that specifies the size of the system Sungevity will install and maintain as well as the monthly amount you will pay Sungevity. A Sungevity Solar Lease comes with a performance guarantee which promises the panels will produce the power agreed to in the contract. And, any power generated above and beyond the guaranteed amount is yours to keep!
PACE
PACE stands for Property Assessed Clean Energy. Many municipalities are setting up PACE programs that help their residents finance a solar system by paying it off through the annual property tax bill. The relatively high interest rate for most PACE programs typically makes PACE financing less cost-effective than a Sungevity Solar Lease. It may, however, be a good option for people who do not live in Sungevity’s service area. Please note that as of the summer of 2010, legal complications are interfering with the rollout of most PACE programs