Mandatory GHG Reporting - Asset Controlling Supplier

This page updated December 18, 2012

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Asset Controlling Suppliers -  System Emission Factors

Pursuant to section 95111(b)(3) of the Regulation for the Mandatory Reporting of Greenhouse Gas Emissions (title 17, California Code of Regulations, section 95100 et seq.), ARB publishes emission factors for all recognized and approved asset-controlling suppliers (ACS) to provide electricity purchasing and selling entities information about potential greenhouse gas emission compliance obligations associated with electricity from these sources.  

For data year 2012, Bonneville Power Administration (BPA) was the only ACS recognized by ARB.  BPA is a federal agency which markets electric power from all of the federally owned hydroelectric projects in the Pacific Northwest.  Section 95111(b)(3) of the MRR specifies that the ACS system emission factor assigned to BPA, which is to be used for emissions data collected in data year 2012 and reported to ARB in 2013, is 20 percent of the default emission factor for unspecified sources. This ACS system emission factor is shown in Table 1.  

Table 1
Asset-Controlling Supplier System Emission Factor
for Data Year 2012 (Reported in 2013)
Bonneville Power Administration (BPA)
ARB ID #4000
0.0856 MT CO2e per MWh


For data year 2013, ARB has recognized and approved two asset-controlling suppliers based on reports submitted and verified pursuant to section 95111(f) of the MRR: BPA and Powerex. Powerex is the wholly-owned electricity marketing subsidiary of BC Hydro – Canada’s third largest electric utility – responsible for marketing BC Hydro’s surplus electricity in the western United States. 


The ACS system emission factors applicable to data year 2013, reported in 2014, are listed in Table 2.


Table 2
Asset-Controlling Supplier System Emission Factors
for Data Year 2013 (Reported in 2014)

Bonneville Power Administration (BPA)
ARB ID #4000

0.0249 MT CO2e per MWh

ARB ID #3101

0.0293 MT CO2e per MWh


Use of Asset-Controlling Supplier System Emission Factors


Electric power entities (EPE) reporting 2012 data to ARB in 2013, and future data in future years, may claim power from an asset-controlling supplier (ACS) only when a power contract for a specified source is in place for those purchases. 


When reporting imported electricity supplied by asset-controlling suppliers under section 95111(a)(5), EPEs must utilize a specified power contract in order to claim ACS power. However, EPEs need not contract directly with an ACS in order to claim ACS power so long as the original buyer and any subsequent buyers and sellers shown in the NERC e-tag market path utilize a specified power contract to convey the right to receive ACS power. 


As amended by the Board in 2012, the definition of “power contract” in section 95102(a) states that a “power contract for a specified source is a contract that is contingent upon delivery of power from a particular facility, unit, or asset-controlling supplier’s system that is designated at the time the transaction is executed.” Acceptable forms of a specified contract may include, but are not limited to, modified versions of either the Western Systems Power Pool (WSPP) Agreement Schedule B (Unit Commitment Service) or Schedule C (Firm Capacity/Energy Sale or Exchange Service) that specify the power is from the ACS system. Other contract forms that specify the source (e.g., a particular facility, unit, or ACS system) at the time of entry into the contract are also acceptable. Unacceptable forms of contract include contracts for a source of electricity that is not a specified source at the time of entry into the transaction to procure the electricity.   

ARB is working on additional guidance for asset controlling suppliers concerning the reporting and verification requirements.

For technical questions about the calculation of the ACS system emission factors, please contact Wade McCartney at or (916) 327-0822.  For general reporting questions, please contact David Edwards at or (916) 323-4887.

Asset Controlling Supplier - Registration by June 1

Electric Power Entities may register as an Asset Controlling Supplier pursuant to 95102(a)(17) and 95111(b)(3). Applicants may download and complete the Asset Controlling Supplier application form here:

ARB has posted an Asset Controlling Supplier (ACS) System Emission Factor Calculation workbook in Excel. This workbook will facilitate entity compliance with the system emission factor calculation in Section 95111(b)(4) and 95111(b)(3).

For entities wishing to be considered an Asset Controlling Supplier for reporting 2014 emissions, please submit your application by June 1st. The submission by this date is needed to ensure sufficient time to process and review the application for the upcoming reporting year. Once the application is completed, please submit the form and attachments.

If you have Electric Power Entity questions please contact Wade McCartney, 916.327.0822.

For emissions data reporting questions, contact, or Patrick Gaffney, 916.322.7303

For general questions regarding Mandatory Greenhouse Gas Emissions Reporting, contact:
Dave Edwards, Manager, Climate Change Reporting Section, 916.323.4887