Net Energy Metering for Biogas Digester Generator

IMPORTANT NOTE: Net Energy Metering for Biogas Digester Generators (NEMBIO) is closed to new customers, pursuant to Senate Bill 489 (Chapter 593, 2011). Eligible biogas digester generators may take service under the NEM Successor Tariff (NEM2). For more information about the NEM 2 Program and how to apply, visit the NEM 2 Program page.

What is NEMBIO?

PG&E’s Net Energy Metering Service for Biogas Customer-Generators (NEMBIO) rate schedule is an optional rate schedule for customers with an eligible biogas digester operated in parallel with PG&E to supply some or all of the customer’s energy needs. A biogas digester is defined as a generating facility used to produce electricity by a manure methane production project or as a byproduct of the anaerobic digestion of bio-solids and animal waste. The generating facility must meet all applicable safety and performance standards established by the National Electrical Code, the Institute of Electrical and Electronics Engineers, accredited testing laboratories such as Underwriters Laboratories and, where applicable, rules of the Public Utilities Commission regarding safety and reliability. Refer to our Interconnection handbook for a technical description of PG&E’s interconnection requirements and procedures. Visit Interconnection handbook.

Download Net energy metering service for Biogas customer-generators (PDF, 156 KB)

Please note that biogas digester generators must commence operation by December 31, 2009, to be eligible for the program according to Public Utilities Code section 2827.9 (the statute governing the NEMBIO program). It also specifies that NEMBIO generators in place as of December 31, 2009, are eligible to take service on this program for the operating life of the biogas digester generating facility. The statute caps availability of NEMBIO to 50 megawatts. Once this limit is reached, the NEMBIO rate will be closed to new customers unless extended by law. Contact PG&E to confirm program availability


NEMBIO works in conjunction with a second rate schedule, referred to as the customer’s otherwise applicable rate schedule (OAS). The OAS is selected by you and can be any PG&E time-of-use (TOU) rate schedule that would be applicable to your account, if you were not on NEMBIO. The significance of the OAS is that it provides not only the charges, but also the export credits for NEMBIO generators. The credits for export will be based on the generation component of your OAS. Other components, such as distribution and transmission, will not be included in calculating credits. NEMBIO customers need to consider their OAS options carefully. You can find complete descriptions (including the components) of all electric rate schedules by visiting our Tariff book. The NEMBIO tariff describes how your credits and charges will be calculated. Download NEMBIO tariff (PDF, 156 KB).

Generating capacity

According to the NEMBIO tariff, most generators interconnected under this rate schedule are limited to no more than 1 megawatt (MW) in generating capacity. As of January 1, 2006, the NEMBIO program now states: "Notwithstanding the generating capacity limit of up to one megawatt stated above, in the service territories of the three largest electrical corporations in the state, up to three large biogas digester electrical generating facilities with a generating capacity of more than one megawatt and not more than 10 megawatts, otherwise meeting the criteria above, shall be eligible for NEMBIO." It is recommended that you contact PG&E as soon as possible if you are considering a project over 1MW in size to check on program availability. 

Best available control technology (BACT) requirements

As of January 1, 2006, all biogas digester generators applying for NEMBIO service must attest that they meet the BACT requirements of their regional air pollution control district at the time of installation in order to be eligible for NEMBIO. You will be required to complete the affidavit in Appendix D of the NEMBIO interconnection agreement regarding these BACT requirements. Download NEMBIO interconnection agreement (PG&E form 79-997, effective 1/1/2006) (PDF, 433 KB).

How does the NEMBIO billing process work?

NEMBIO billing includes an annual true-up of usage and generation. Credits are based on the generation component of the energy charge in the OAS. You will be billed monthly for all other charges. The details of the billing are explained in the NEMBIO tariff. Download NEMBIO tariff (PDF, 156 KB).

NEMBIO requires PG&E to use a TOU meter capable of separately registering the flow of electricity in two directions (that is, bi-directional). If your existing meter is not bi-directional, you shall be responsible for all expenses involved in purchasing and installing a bi-directional PG&E meter.


Applying generation credit to other accounts (for dairy customers only)

PG&E will aggregate the load (usage) of all eligible metered Time-of-Use (TOU) accounts associated with your dairy operations designated on the interconnection agreement to determine NEMBIO credits and/or charges annually. All of the aggregated TOU metered service account(s) serving the dairy operation must be located on property adjacent, or contiguous, to the NEMBIO dairy facility including but not limited to accounts associated with the milking operations, milk refrigeration, or water pumping of the eligible dairy. All such metered service accounts must be under the same ownership and name as the account serving the NEMBIO account. As a general rule of thumb, PG&E recommends interconnecting the biogas digester generating facility on the account with the greatest load.


Starting your application

Distributed generation interconnection procedures are contained in Rule 21 (PDF, 7.52 MB).

The initial documents required are:

ItemGeneral Comments

Make sure that all applicable sections for your generator are completed. Contact us if you have any questions about this form.

Site Plan

Show generator location with respect to building, transformer, main switchboard, utility disconnect switch and other pertinent electrical equipment.

Single Line Drawing

Must include net generation meter (if required) and utility disconnect switch with manufacturer and model number.

Three Line Drawing

Required if the generator is not certified or an external relay is used.

Proposed Relay Settings

Required if the generator is not certified or an external relay is used.

Protection Operating Description

Required if the generator is not certified or an external relay is used.

Submit the application package to PG&E by registered U.S. mail.

Mailing Address:
Pacific Gas and Electric Company
Interconnection Services
Mail Code N7L
P.O. Box 770000
San Francisco, CA 94177-0001

The Review Process

PG&E will conduct some or all of the following interconnection reviews to determine the interconnection requirements for a generation project.

Application review
The application shall normally be acknowledged and reviewed for completeness within 10 business days of receipt of application. The application must be deemed complete before moving on to the initial review.

Initial review
The review shall be completed, absent of any extraordinary circumstances, within 10 business days of deeming the application complete. The review will determine if your generation facility qualifies for a simplified interconnection or if a supplemental review is required.

Supplemental review
The review, if required, should be completed within 20 business days of deeming the application complete. The review will determine if your generation facility can be interconnected or if a Detailed Interconnection Study is required.

Detailed interconnection study
You must enter into an agreement with Pacific Gas and Electric Company to perform such additional studies, facility design/engineering and to provide detailed cost estimates for fixed price or actual cost billing should interconnection upgrades be required. The study may be at your expense.


Prior to interconnection, both PG&E and you must execute the following agreements:

Interconnection agreement for net energy metering of qualifying biogas digester generating facilities (PG&E form 79-997, effective 1/1/2006): This agreement provides for the applicant to interconnect and operate its generating facility in parallel with Pacific Gas and Electric Company’s distribution system and establishes the ongoing business relationship between you and Pacific Gas and Electric Company including operating and communication protocols. The NEMBIO Customer–Generator must list any qualifying accounts eligible for aggregation under Special Condition 2 of Schedule NEMBIO. As a part of completing the interconnection agreement, PG&E also requires that you submit Proof of Liability Insurance. You must provide and maintain general liability insurance with a combined single limit in accordance with Section 9 of the "Interconnection Agreement for Net Energy Metering of Qualifying Biogas Digester Generating Facilities." Download Interconnection agreement for net energy metering of qualifying biogas digester generating facilities (PG&E form 79-997, effective 1/1/2006) (PDF, 433 KB).

Special Facilities Agreement: This agreement specifies the cost for special metering required for NEMBIO. Additionally it may include interconnection facilities to be constructed and owned by Pacific Gas and Electric Company as needed for your project. The agreements will be prepared by a Generation Interconnection Services (GIS) project manager after the completion of the review and study process and sent to you for execution. The GIS project manager will work with you to ensure that the appropriate agreements are properly prepared, at the appropriate time, and guide your project to interconnection.


When you notify PG&E that the facility is ready, be aware that scheduling an inspection can take up to 10 days for certified generators with no external relays and up to 30 days for all other generators. The following items must be completed prior to the scheduling of the inspection:


  • Execute all required agreements
  • Completion of all electric work by Pacific Gas and Electric Company
  • Completion of (utility-owned) electric service
  • PG&E approval of the single line and three line relay drawings


And the following documents must be received:


When the inspection has been successfully completed, PG&E will issue a "Permission to Parallel" letter authorizing operation of the generator in parallel with PG&E’s distribution system. Generators may not interconnect with PG&E’s distribution system without written authorization.