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General Terms and Definitions

Certified solar and wind

Click here for interconnection inverter-based certified solar and wind general steps.

Connected Capacity

The output capability of a Distributed Generation (DG) Facility before applying any protective or operational limitations. This is most often the nameplate capability of generating systems or the rated capability of inverters used in renewable DG systems.

Distribution rate schedules

Click here to see the schedules.

Distributed renewable generation (DRG)

Electric generation from a renewable energy source with a capacity of less than 2,000 kilowatts that is installed on a retail electric customer's side of the meter. Renewable energy sources include sun, wind, geothermal, hydroelectric, wave or tidal energy, and biomass or biomass-based waste products, including landfill gas. They do not include fossil fuels, waste products from fossil fuels, or waste products from inorganic sources.

DRG meter

A meter that separately measures in-flow and out-flow energy at the Oncor point of common coupling, also known as the point of delivery. A DRG meter is also known as a dual register meter or an in-flow/out-flow meter.

DRG system

DRG systems describe a generator that produces energy from renewable sources, such as solar photovoltaic (PV) panels and on-site wind generators and is interconnected to the electric utility's distribution system at voltages less than 60 kV.

Electric Reliability Council of Texas (ERCOT)

ERCOT manages the flow of electric power to 24 million Texas customers representing about 90% of the state's electric load. ERCOT as the independant system operator administers customer switching in competitive choice areas, manages financial settlement for the competitive wholesale bulk-power market and transmits consumption and/or generation meter data between REPs, Oncor and other utilities, and ERCOT.

Electric Service Identifier (ESI ID)

A 17-digit customer identification number found on your electric bill. The first 10 digits represent the Oncor company code, either 1044372000 or 1017699000, and the remaining seven digits are a unique code for your specific account.

Impact study

An Oncor study to determine how its system will be impacted by the interconnection of proposed customer-owned generation. This study specifies and identifies the modifications that will be needed on the Oncor system for a reliable interconnection. The Pre-Interconnection Study Fee schedule is included in the interconnection Application and can be obtained here.

In-flow kWh

Energy flowing from the grid to the customer. Oncor smart meters show an in-flow kWh (001) display register which represents the cumulative customer consumption, similar to your car odometer. Yesterday's reading subtracted from today's reading would yield one day of kWh usage, if your meter multiplier is one.

Interconnection Agreement

The standard form of agreement, which has been approved by the Public Utility Commission of Texas (PUCT). The agreement sets forth the contractual conditions under which a company and a customer agree that one or more facilities may be interconnected with the company's utility system. Oncor will forward this agreement to you after you submit a completed interconnection application. You can find a form of the agreement on our website. Select "Tariff for Retail Delivery Service (PDF)." In Chapter 6, Section 6.3.4, you will find the Agreement for Interconnection and Parallel Operation of Distributed Generation.

Interconnection Agreement effective date

The Interconnection Agreement becomes effective when executed by both Oncor and the customer. The effective date is the latter of the Oncor or customer signature dates.

Interconnection Application
PUCT approved tariff application used to submit a request to Oncor for interconnection of customer-owned generation. It asks for information such as name, address, generator size, generator type and one-line diagram. For a copy of the application, click here.

Layout sketch

Shows the plan view (overhead) of the physical layout of the generating system which includes the Oncor meter,  the visible, lockable and labeled AC disconnect (VLLD) and customer's generation. One of the requirements of the layout sketch is to identify if the VLLD is near the Oncor meter. i.e. within10 feet and in a readily accessible location. This sketch is not required to show a high level of detail for the entire system, but identify the components listed above.

Oncor placard guideline

Oncor's requirements related to specifications for safety placard guidelines. To get the guideline go to: Interconnection Application Request and select Oncor Placard Guideline.

One-line diagram

A diagram that shows the sequence of switches, breakers, devices, etc. starting at the Oncor meter and continuing to the customer's generator. This diagram shows the location of the visible AC disconnect in relation to the Oncor meter and other equipment in the electrical circuit.

Operating Capacity

The output capability approved for online operations with the utility system. In some cases, customers operate their DG Facilities with only a portion of the Connected Capacity at a given point in time. Other customers may have spare generating capacity and limit what is used at a given point in time.

Out-flow kWh

Energy flowing out from the customer to the grid. An advanced meter shows the out-flow kWh (057) display register which represents cumulative excess generation. Yesterday's reading subtracted from today's reading would yield one day of kWh generated and sent to the grid, if your meter multiplier is one.

Public Utility Commission of Texas (PUCT)

The state agency that regulates Texas' electric and telecommunication utilities, implements respective legislation and offers customer assistance in resolving consumer complaints.

Retail Electric Provider (REP)

A person or entity that sells energy to retail customers in competitive areas of Texas. A REP may not own or operate generation facilities. A REP may purchase energy, including out-flow energy, from a distributed generation customer.

REP agreement

The confidential agreement between you and your REP to buy electricity (in-flow kWh) and, if applicable, to sell excess generation (out-flow kWh).

Service study

Generally performed for smaller certified solar and wind systems and covers many of the same issues as an impact study.


A website sponsored by a consortium of electric transmission and distribution utilities in Texas. If you have an advanced/smart meter, you can visit smartmetertexas.com to find out how much energy you’re using and make smart decisions to help lower your energy bills.

Transmission and Distribution Utility (TDU)

 Oncor is a TDU – a Texas company that owns or operates for compensation equipment or facilities to transmit or distribute electricity. This does not include a municipally-owned utility or an electric cooperative. A TDU may also be referred to as a Transmission and Distribution Service Provider (TDSP).  For additional information, refer to PUCT Substantive Rule 25.5(139).

Visible, Lockable and Labeled AC Disconnect (VLLD)

A switch that isolates the customer's generation from the utility system. The VLLD is not a breaker. It’s a switch – usually with a handle on the side – and should have a visible air gap for a utility lineman to verify that the alternate source of power is open. The switch should be labeled in accordance with National Electrical Code (NEC) specifications and should be within 10 feet of the Oncor meter.

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All Rights Reserved.