Arizona Solar Energy Systems: Key Terms and Glossary

Arizona's solar industry operates within a layered framework of state statutes, utility tariffs, building codes, and federal incentive programs — each with its own specialized vocabulary. This glossary page defines the core terms used across Arizona solar energy system design, permitting, installation, and operation. Understanding these definitions helps property owners, contractors, and analysts interpret utility agreements, permit applications, and system specifications accurately. For a broader orientation to how these systems function in practice, the Arizona Solar Energy Systems conceptual overview provides a process-level complement to this reference.

Definition and scope

A solar energy system, as defined under Arizona Revised Statutes § 33-439, means a system that uses solar devices to collect, store, or distribute solar energy. Arizona law distinguishes between solar thermal systems (which convert sunlight into heat for water or space heating) and photovoltaic (PV) systems (which convert sunlight directly into electricity). These two categories carry different permitting tracks, different utility interconnection requirements, and different incentive structures.

Scope of this page: This glossary covers terminology applicable to residential and commercial solar energy systems installed within the state of Arizona. It draws on Arizona Revised Statutes, Arizona Corporation Commission (ACC) rules, Arizona Department of Revenue guidance, and relevant federal definitions from the U.S. Department of Energy. Terms related to federal-only programs (such as Investment Tax Credit mechanics governed exclusively by IRS code) are defined at a structural level only — the federal ITC page addresses those details. This page does not cover solar installations in other states, tribal land installations subject to separate sovereign jurisdiction, or utility-scale generation projects governed by FERC rather than the ACC. HOA-related solar rights, addressed under Arizona HOA rules and solar rights, are referenced here only at a definitional level.

How it works

Solar energy system terminology maps to four functional layers: generation, conversion, storage, and grid interaction. The key terms within each layer are defined below.

Generation layer

• Photovoltaic (PV) cell: The fundamental semiconductor unit that generates direct current (DC) electricity when exposed to photons. Standard silicon-based cells convert roughly 15–rates that vary by region of incident sunlight into electricity (U.S. Department of Energy, Office of Scientific and Technical Information).
• Solar module (panel): An assembly of PV cells encapsulated in a weatherproof frame. Rated output is expressed in watts-peak (Wp) under Standard Test Conditions (STC): 1,000 W/m² irradiance, 25°C cell temperature, AM 1.5 spectrum.
• Array: The complete collection of modules installed at a site, wired in series strings or parallel branches.
• Irradiance: Solar power per unit area, measured in W/m². Arizona's statewide average peaks at approximately 5.5–6.5 peak sun hours per day — among the highest in the continental United States (National Renewable Energy Laboratory, PVWatts Calculator). See solar irradiance and sun hours in Arizona for location-specific data.

Conversion layer

• Inverter: The device that converts DC electricity from the array into alternating current (AC) electricity compatible with building loads and the utility grid. Three primary inverter types are relevant to Arizona installations:
• String inverter: One centralized inverter processes output from an entire string of modules. Lower cost; performance degraded if any module is shaded.
• Microinverter: One inverter per module. Higher per-unit cost; module-level maximum power point tracking (MPPT) mitigates shading losses.
• Power optimizer + string inverter (DC optimizer): Module-level DC conditioning feeds a central string inverter. Intermediate cost and performance profile.
• Maximum Power Point Tracking (MPPT): An algorithm that continuously adjusts electrical operating point to extract maximum available power from modules under varying irradiance and temperature.

Storage layer

• Battery energy storage system (BESS): An electrochemical storage device paired with a PV system. Arizona's high grid rates under time-of-use (TOU) tariffs from utilities including Arizona Public Service (APS) and Salt River Project (SRP) make battery storage economically relevant. Common chemistries in residential Arizona installations are lithium iron phosphate (LFP) and nickel manganese cobalt (NMC). See Arizona solar battery storage overview.
• State of Charge (SoC): The percentage of total usable capacity currently available in a battery. Systems are typically configured with a minimum SoC floor (commonly 10–rates that vary by region) to protect battery longevity.
• Depth of Discharge (DoD): The percentage of rated capacity discharged in a single cycle. Higher DoD per cycle generally reduces total cycle life.

Grid interaction layer

• Net metering / net energy metering (NEM): A billing mechanism under which excess PV generation exported to the grid offsets future consumption charges. Arizona's NEM policy is governed by ACC decisions; Tucson Electric Power (TEP) and APS operate under ACC-approved tariffs. Full details appear at Arizona net metering policies and utility billing.
• Interconnection agreement: The contract between a system owner and the utility authorizing parallel operation with the grid. Governed in Arizona by utility tariffs filed with the ACC and by IEEE Standard 1547-2018 technical requirements.
• Anti-islanding protection: A safety function required by UL 1741 and IEEE 1547 that forces an inverter to cease export if the utility grid de-energizes, preventing energization of downed conductors.

Common scenarios

Arizona solar terminology appears across four recurring application scenarios, each with distinct classification boundaries.

1. Grid-tied residential PV system

The most common Arizona configuration. The system comprises a rooftop or ground-mounted array, a string or micro-inverter, an AC disconnect, and a utility-interactive interconnection. No battery is required. The system qualifies for the Federal Investment Tax Credit (ITC) and Arizona's residential solar income tax credit under Arizona Revised Statutes § 43-1083, which provides a credit equal to rates that vary by region of installed cost, capped at amounts that vary by jurisdiction per system (Arizona Department of Revenue).

Contrast — grid-tied vs. off-grid: A grid-tied system exports and imports power freely; an off-grid system operates in isolation and requires battery storage sized to cover rates that vary by region of load during low-irradiance periods. See Arizona grid-tied vs. off-grid solar systems for a full comparison. Off-grid systems face different permit classifications in Arizona and are not subject to utility interconnection agreements.

2. Commercial and industrial (C&I) PV system

Larger arrays (typically 25 kW–2 MW AC) on commercial rooftops or ground mounts. C&I systems may involve demand charge management strategies, three-phase inverters, and Power Purchase Agreements (PPAs). See residential solar vs. commercial solar in Arizona and commercial solar incentives in Arizona.

3. Battery-paired hybrid system

A PV array paired with a BESS for self-consumption optimization or backup power. Relevant terms include backup gateway, critical load panel, and islanding mode — the last being the operating state where the system intentionally disconnects from the grid and serves only designated loads during an outage.

4. Community solar subscription

A subscriber does not own on-site generation but purchases a share of a remote array's output, receiving a bill credit. Arizona's community solar landscape is covered at Arizona community solar programs.

Decision boundaries

Accurate application of solar terminology requires understanding where classification lines fall.

Numbered classification boundaries:

1. System size threshold for simplified interconnection: Arizona utilities typically apply a fast-track interconnection process to systems below 10 kW AC (residential) without additional engineering review, per ACC-approved interconnection tariffs.
2. Commercial licensing threshold: Arizona contractors must hold a Registrar of Contractors (ROC) license in the appropriate solar classification (C-72 Dual Element, or Electrical CR-11) regardless of system size. Licensing requirements are detailed at Arizona solar contractor licensing requirements.
3. Storage fire code trigger: Battery systems exceeding 20 kWh of energy storage capacity in residential occupancies require additional review under NFPA 855 and Arizona Fire Code amendments.
4. Permit requirement: The Arizona State Fire Marshal and local Authority Having Jurisdiction (AHJ) require building and electrical permits for all grid-tied PV installations regardless of size. The permitting process is described at permitting and inspection concepts for Arizona solar energy systems — nahb.org
5. U.S. Bureau of Labor Statistics, Occupational Outlook Handbook — bls.gov/ooh
6. International Code Council (ICC) — iccsafe.org

Related resources on this site:

• Arizona Solar Energy Systems: What It Is and Why It Matters
• Types of Arizona Solar Energy Systems
• Process Framework for Arizona Solar Energy Systems