Renewable energy glossary


Affected Utility
A public service corporation serving retail electric load in Arizona, but excluding any utility distribution company with more than half of its customers located outside of Arizona.

Alternating Current (AC)
An electric current that reverses its direction at regularly recurring intervals, such as that used to provide electric service to electric utility customers.

Annual Renewable Energy Requirement
The portion of an affected utility’s annual retail electricity sales that must come from eligible renewable energy resources.

Arizona Corporation Commission (ACC)
The public utilities commission that regulates rates, operations and other aspects of most electric and gas utilities in Arizona.


Methane and other combustible gases released from the decomposition of organic materials.


Centralized Solar
A thermal solar facility that concentrates sunlight in order to collect heat and use that heat to create steam which then drives a steam turbine creating electric generation (also referred to as concentrating solar thermal).

Commercial Operation Date (COD)
The date which the generating resource started commercially producing power.

Concentrating Solar Power (CSP or CPV)
CSP technologies use mirrors to reflect and concentrate sunlight onto receivers that collect solar energy and convert it to heat. This thermal energy can then be used to produce electricity via a steam turbine or heat engine that drives a generator.

Conventional Energy Resource
An energy resource that is non-renewable in nature, such as natural gas, coal, oil, and uranium, or electricity that is produced with energy resources that are not renewable energy resources.

Customer Self-Directed Renewable Energy Option
A program approved by the ACC under which an Eligible Customer may self-direct the use of its allocation of funds collected pursuant to an Affected Utility’s Tariff.


Direct Current (DC)
An electric current that flows in one direction, such as with batteries and solar cells.

Dual-axis solar trackers
The trackers continually face the sun because they can move in two different directions. Types include tip-tilt and azimuth-altitude. Dual-axis tracking is typically used to orient a mirror and redirect sunlight along a fixed axis towards a stationary receiver.

Distributed Generation
Electric generation sited at a customer premises, providing electric energy to the customer load on that site or providing wholesale capacity and energy to the local utility distribution company for use by multiple customers in contiguous distribution substation service areas. The generator size and transmission needs shall be such that the plant or associated transmission lines do notrequire a certificate of environmental compatibility from the ACC.

Distributed Renewable Energy Requirement
A portion of the annual renewable energy requirement that must be met with renewable energy credits derived from resources that qualify as distributed renewable energy resources pursuant to R14-2-1802(B).

Distributed Solar Electric Generator
Electric generation sited at a customer premises, providing electric energy from solar electric resources to the customer load on that site or providing wholesale capacity and energy to the local utility distribution company for use by multiple customers in contiguous distribution substation service areas. The generator size and transmission needs shall be such that the plant or associated transmission lines do not require a certificate of environmental compatibility from the ACC.


Eligible Customer
An entity that pays Tariff funds of at least $25,000 annually for any number of related accounts or services within an affected utility’s service area.

Extra Credit Multiplier
A way to increase the Renewable Energy Credits attributable to specific Eligible Renewable Energy Resources in order to encourage specific renewable applications.


Fixed Tilt System (Fixed PV)
For a fixed PV array, the tilt angle is the angle from horizontal of the inclination of the PV array (0° = horizontal, 90° = vertical).


Green Pricing
A rate option in which a customer elects to pay a tariffed rate premium for electricity derived from Eligible Renewable Energy Resources.


Linear Concentrating Solar Power (CSP or LCPV)
Collectors capture the sun's energy with large mirrors that reflect and focus the sunlight onto a linear receiver tube.


Market Cost of Comparable Conventional Generation
The Affected Utility’s energy and capacity cost of producing or procuring the incremental electricity that would be avoided by the resources used to meet the Annual Renewable Energy Requirement, taking into account hourly, seasonal, and long-term supply and demand circumstances. Avoided costs include any avoided transmission and distribution costs and any avoided environmental compliance costs.


Net Billing
A system of billing a customer who installs an Eligible Renewable Energy Resource generator on the customer’s premises for retail electricity purchased at retail rates while crediting the customer’s bill for any customer-generated electricity sold to the affected utility at avoided cost.

Net Metering
A system of metering electricity by which the affected utility credits the customer at the full retail rate for each kilowatt-hour of electricity produced by an eligible renewable energy resource system installed on the customer-generator’s side of the electric meter, up to the total amount of electricity used by that customer during an annualized period, and which compensates the customer-generator at the end of the annualized period for any excess credits at a rate equal to the affected utility’s avoided cost of wholesale power. The affected utilitydoes not charge the customer generator any additional fees or charges or impose any equipment or other requirements unless the same is imposed on customers in the same rate class that the customer generator would qualify for if the customer-generator did not have generation equipment.


Owned (TEP owned or UES owned)
The utility owns, operates, and maintains the photovoltaic (PV) system, in which the Utility can either own the land or lease it from a third party under an agreement term.


Photovoltaic Solar
Solar generation that uses photovoltaic panels to convert sunlight directly to energy.

Previous Company
The name of a developer or company that previously owned or developed the project. In many cases, renewable energy projects are initiated by one company and later sold to another company.

Purchase Power Agreement (PPA)
A financial arrangement in which a third-party developer owns, operates, and maintains the photovoltaic (PV) system, and a host customer agrees to site the system on its roof or elsewhere on its property and purchases the system's electric output from the solar services provider for a predetermined period.


Renewable Energy Credit
The unit created to track kWh derived from an eligible renewable energy resource or kWh equivalent of conventional energy resources displaced by distributed renewable energy resources.

Renewable Energy Resource
An energy resource that is replaced rapidly by a natural, ongoing process and that is not nuclear or fossil fuel.

Renewable Resource
A resource whose energy source is not permanently used up in generating electricity. A resource that uses solar, wind, hydro, geothermal, biomass, or similar sources of energy to either generate electric power or reduce the customer electric power requirements.


Single-axis solar trackers
The trackers rotate on one axis moving back and forth in a single direction. Different types of single-axis trackers include horizontal, vertical, tilted, and polar aligned, which rotate as the names imply.

Solar Energy
Most renewable energy comes either directly or indirectly from the sun. Sunlight, or solar energy, can be used directly for heating and lighting homes and other buildings, for generating electricity, and for hot water heating, solar cooling, and a variety of commercial and industrial uses.

Solar Hybrid
A thermal solar facility with the ability to supplement heat from the sun with heat derived by burning natural gas.

Solar thermal collector
A device designed to receive solar radiation and convert it to thermal energy. Normally, a solar thermal collector includes a frame, glazing, and an absorber, together with appropriate insulation. The heat collected by the solar collector may be used immediately or stored for later use. Solar collectors are used for space heating; domestic hot water heating; and heating swimming pools, hot tubs, or spas.


A Commission-approved rate designed to recover an affected utility’s reasonable and prudent costs of complying with these rules.

The length of time for which TEP or UES will procure power from the resource. “Own” represents units owned by TEP or UES. “20” means the power is procured under a 20-year power purchase agreement.


Utility distribution company
A public service corporation that operates, constructs, or maintains a distribution system for the delivery of power to retail customers.


Wind energy
Kinetic energy present in wind motion that can be converted to mechanical energy for driving pumps, mills, and electric power generators.

Wind power plant
A group of wind turbines interconnected to a common utility system through a system of transformers, distribution lines, and (usually) one substation. Operation, control, and maintenance functions are often centralized through a network of computerized monitoring systems, supplemented by visual inspection. This is a term commonly used in the United States. In Europe, it is called a generating station.

Wind turbine
Wind energy conversion device that produces electricity; typically three blades rotating about a horizontal axis and positioned up-wind of the supporting tower.

The Renewable Energy Application Status report offers details about:

  • Applications to interconnect to TEP’s electrical grid for customer-owned, leased and new construction solar projects
  • Program budgets
  • Average system size of residential photovoltaic systems