Alternating Current or AC

AC is the form of electricity that is delivered to your home or business by an electric utility. Solar PV systems produced DC, which must be converted to AC by an inverter.




Any number of electrically connected PV panels providing a single electrical output.



Capacity Rating

The rating given to a PV system by its manufacturer denoting the load the system is able to meet or supply when operating at full capacity in direct sunlight with no shade.


CEC-AC Rating 

The calculation that provides a total estimated energy output of a solar generation system, factoring in the efficiency of the panels and inverter. The CSI Program Administrators use the California Energy Commission's CEC-AC method to measure nominal output power of PV cells or modules to determine the system's rating in order to calculate the appropriate incentive level(number of modules multiplied by the module Performance Test Conditions rating multiplied by the inverter efficiency).


Conversion Efficiency

The amount of the sun's energy that a solar cell can convert into electricity; the balance is lost as heat or reflected light.


Design Factor

The design factor is a CSI term that compares a proposed system's expected generation output with that of a baseline system. The design factor allows the CSI Program Administrators to pay a higher incentive to optimally designed systems. The design factor is calculated using a few key inputs in the EPBB Calculator available a


 DC energy comes from the sun.

DC energy comes from the sun.

Direct Current or DC

Solar PV systems produce electricity in DC, which is defined as the continuous flow of electricity through a conductor. DC power is converted to AC by an inverter to power homes and businesses.



Greenhouse Gas (GHG)

The gases responsible for trapping heat form the sun within Earth's atmosphere (i.e., water vapor, carbon dioxide, methane, ozone, chlorofluorocarbons and nitrogen oxides). GHGs are released from many sources, including industrial processes such as power generation from fossil fuels.




A network of power stations, transmission circuits and substations that conduct electricity and provide it to homes and businesses for their use. 



Grid-Connected or Grid-Tied PV System

 A PV system in which the PV array is wired into buildings or residences that are connected to the utility grid. This allows customers to feed excess electricity into and pull needed electricity from the grid. To receive rebates from the CSI Program, PV systems must be connected to the utility’s grid. 

Interconnection Agreement

A legal document between the customer and their electric utility authorizing the connection of the customer’s solar generation system to the utility’s grid. This agreement is required prior to your utility granting permission to operate and your PA paying the CSI rebate. 


 SolarEdge Inverter

SolarEdge Inverter


 A device that converts DC electricity produced by a solar generation system into AC electricity that can be used in a home or business. Some energy is lost when this conversion takes place (see CEC-AC rating). 


Inverter Efficiency

 The AC power output of the inverter divided by the DC power input. Inverter efficiency is lowest when operating at low loads; thus, it is important to select inverters of the proper size relative to the PV array. 


Kilowatt or kW

A unit of electrical power equal to 1,000 W, which constitutes the basic unit of electrical demand. The Watt is a metric measurement of power (not energy) and is the rate (not the duration) at which electricity is used. 1,000 kW is equal to one megawatt (MW). 


Kilowatt-Hour or kWh

A unit of electrical energy, equivalent to the use of one kW of electricity for one full hour. Utilities measure customers’ electric energy usage based on kWh, and electricity rates are most commonly expressed in cents per kWh. The CSI Program’s PBI incentive is paid based on the kWh of energy produced by a solar generation system. 



The amount of power consumed by an electric customer at a specific time. Base load is the minimum constant level of electricity required by utility customers; peak load is the amount of electricity required at the time of greatest demand. 


Megawatt or MW

Unit of electric power equal to 1,000 kW or 1 million Watts. 



A device used to measure and record the amount of electricity used and/or generated by a consumer. 



A module is the smallest protected assembly of interconnected PV cells. Modules are rated typically from 40 to 300 Watts. 



A term used to describe the direction that a solar module faces. The two components of orientation are the tilt angle (the angle of inclination a module makes from the horizontal) and the azimuth (the compass angle that the module faces, with north equal to 0 degrees and south equal to 180 degrees). 


Photovoltaic or PV

The technology that uses a semiconductor (such as silicon) to convert sunlight directly into electricity. 


Program Administrator or PA

Refers to PG&E, SCE and CCSE, who administer the CSI Program under the auspices of the California Public Utilities Commission (CPUC), in the service territories of IOUs. CCSE administers the CSI Program in the SDG&E service territory. 


Renewable Energy Credits or RECs

Also known as green certificates, green tags or tradable renewable certificates, RECs represent the environmental attributes of the power produced from renewable energy projects. By installing a renewable energy system (such as solar), you become the owner of these environmental attributes, or RECs. 


System Size

System size is the electricity generating capacity of a given photovoltaic system based on CEC-AC rating standards. In the CSI Program, the system size is limited to no greater than the amount of total electricity consumed at a site during the prior 12 months.  


Time-of-Use or TOU Rates

An electricity pricing plan in which the cost of electricity varies depending on the time period in which the energy is consumed or produced. In a TOU rate structure, higher prices are charged during utility peak-load times. Such rates can provide an incentive for consumers to curb power use during peak times. Solar PV panels tend to produce power during peak times, so they have higher value when used in conjunction with TOU rates. 


Tracker or Tracking Array

A number of PV modules mounted such that they track the movement of the sun across the sky to maximize energy production, either with a single-axis or dual-axis mechanism. 


Watt or W

A unit of measurement of electric power, named after physics pioneer James Watt.