1

Technical Support Document: Net Energy Output Monitoring and Reporting 

Draft 4/8/2014 

Table of Contents 

Background...................................................................................................................................................2

Monitoring of Electric Generation................................................................................................................ 3

Equipment standards.................................................................................................................................3

Specification and frequency of quality assurance testing ......................................................................... 4

Proposed definition of net electric output................................................................................................. 4

Default apportionment of parasitic loads to multiple units....................................................................... 5

Monitoring of Non-electric Output at CHP units.......................................................................................... 5

Reporting of Net Electric Generation and CHP Net Energy Output ............................................................ 6

Reporting of Monitoring Plan Data and Quality Assurance Testing Data.................................................... 7

 
2

Background

This document provides additional information relating to the proposed Emission 

Guidelines for Greenhouse Gas Emissions from Existing Stationary Sources: Electric Utility 

Generating Units. It is intended to discuss topics regarding the monitoring and reporting of net 

output energy at electric generating units (EGUs) for which the agency is seeking comments in 

the proposal. 

The proposed emission guidelines would establish a rate based emissions performance 

goal for each state on a net energy output basis. A state could meet this goal by establishing 

greenhouse gas emissions rate standards for EGUs for which EGUs would need to monitor 

emissions and net energy output. Emissions and net energy output data would be monitored and 

reported under 40 CFR Part 75 and would be reported via the Agency’s Emissions Collection 

and Monitoring Plan System (ECMPS). 

Currently, reporting under 40 CFR Part 75 under the Acid Rain Program requires the 

reporting of gross load (either electric or steam) for the main purpose of apportioning emissions 

to units that are monitored at a common stack and establishing load bins for data substitution 

procedures. Currently, under Part 75 reporting, there are no quality assurance requirements for 

gross load because it is presumed that the operator of an EGU would have the accurate 

monitoring of generation in its best interest and because the Acid Rain Program and other cap 

and trade programs require compliance on a mass basis and not a rate basis, so generation data is 

not necessary for compliance purposes. 

Under the proposed emission guidelines, reported energy output data would be used for 

compliance purposes. Therefore, quality assurance of output data is as important as quality 

assurance of emissions data. The EPA is proposing and taking comment on requiring states to 

use net energy output as the measure for any rate based emission standards. A rate-based 

standard, whether gross or net, would necessitate quality assurance of output data above and 

beyond what is currently required under Part 75 to ensure that all output data are of the same 

quality. 

 
3

Monitoring of Electric Generation 

Electricity is used at power plants for a variety of purposes and is commonly described as 

auxiliary or parasitic load. The EPA understands that electric generation and parasitic loads are 

universally measured at EGUs. These parasitic loads can include any of the following: electric 

motors used for pumps, fans, air compressors, coal handing equipment (such as conveyor belts 

and pulverizers), gas turbine starters, air pollution control equipment (such as electrostatic 

precipitators), and building use (such as lighting, air conditioning, computer systems, etc.). Gross 

generation is measured at the generator terminals (via current and potential transformers) enroute 

to the unit high voltage step up transformer, plant HV switchyard, and transmission into the 

electric grid. A unit auxiliary transformer typically steps down generator voltage to provide 

separately measured medium voltage electricity to in plant auxiliary/parasitic loads. Station 

service transformers typically provide separately measured electricity from the grid to plant 

auxiliary loads when the EGU is not in operation or is starting up. The EPA understands that 

steam boiler based plants typically have station service transformers, while combustion turbine 

based plants commonly do not have separate station service transformers and back feed through 

unit and unit auxiliary transformers to measured aux loads when the EGU is not operating or is 

starting up. Given these measurements commonly occur at EGUs, the EPA understands that the 

equipment needed to convert gross generation to net generation on an hourly basis exists at all 

EGUs. 

Equipment standards 

The EPA understands that there are several equipment standards including those that 

require 0.2 accuracy meters and 0.5 accuracy meters. The American national Standards Institute 

(ANSI) published an American National Standard for Electricity Meters – 0.2 and 0.5 Accuracy 

Classes (ANSI C12.20-2010) and published a Code for Electricity Metering: ANSI C12.1-2008. 

The EPA is seeking comment on the proposed requirement that would specify 0.2 accuracy class 

meters to determine net electric output (or gross electric output). The EPA is seeking comment 

on the use of ANSI C12.20 to specify the minimum accuracy of equipment that would be used to 

measure net electric output under the proposed emissions guidelines. The EPA is seeking 

comments on the use of equipment standards that would ensure a level playing field regarding 

the minimum acceptable accuracy of equipment used to measure net electric generation while 
4

minimizing any additional burden of upgrading equipment used to measure net electric 

generation. 

Specification and frequency of quality assurance testing 

The EPA understands that, on a regular basis, EGUs typically perform checks on their 

electricity meters to ensure that the equipment is operating as designed. The EPA is seeking 

comments on the specifications of such checks and the frequency at which they are typically 

performed. The EPA is seeking comments on industry’s best practices that would ensure 

adequate net electricity measurement accuracy while minimizing additional burden of quality 

assurance testing procedures. 

Proposed definition of net electric output 

The EPA is proposing the following definition: 

Net-electric output means the amount of gross generation the generator(s) produce 

(including, but not limited to, output from steam turbine(s), combustion turbine(s), and 

gas expander(s)), as measured at the generator terminals, less the electricity used to 

operate the plant (i.e., auxiliary loads); such uses include fuel handling equipment, 

pumps, fans, pollution control equipment, other electricity needs, and transformer losses 

as measured at the transmission side of the step up transformer (e.g., the point of sale). 

For hours or partial hours when there is no gross generation, net electric output shall be 

zero. Measurements must be performed using 0.2 accuracy class electricity metering 

instrumentation and calibration procedures as specified under ANSI Standards No. 

C12.20. 

The EPA is seeking comment on this definition, especially regarding the specification of 

the 0.2 accuracy class meters. The EPA is also seeking comment on the treatment of externally 

provided electricity when the unit is not operating or begins to start up in the determination of 

net electric output. Under this definition, grid supplied electricity (or other externally provided 

electricity) that is used at the station when the EGU has no gross generation, (such as when the 

EGU is not operating or when the EGU is beginning to start up) would not be subtracted from 

the zero gross generation, which would prevent net generation from being negative. This would 
5

effectively only subtract electricity that is used by the plant and that is derived from unit from 

gross generation. 

Default apportionment of parasitic loads to multiple units 

For plants that have more than one unit, apportionment of parasitic loads that share 

common auxiliary transformers would be necessary. The EPA is taking comment on a default 

system of apportioning parasitic loads among multiple EGUs. The proposed default 

apportionment, as mentioned in the preamble of the proposal, would be to apportion net 

generation to each unit at a facility that shares common auxiliary transformers or a common bus 

to the grid by the gross generation of each of the generators. For combined cycle units, the gross 

generation of the steam turbine would be apportioned to each combustion turbine by the gross 

load of each combustion turbine, as currently prescribed in the Part 75 Emissions Monitoring 

Policy Manual, question 17.2. There may be unique transformer and parasitic load configurations 

at a plant with multiple units that would make the default apportionment of net generation to 

each unit problematic. For example, if two units share a common steam header and a common 

generator, there are not two gross generation values to apportion the net electric generation. 

Also, for example, if two units have parasitic loads that are on a shared auxiliary transformer and 

if the equipment that serves one of the units typically uses a lot more electricity than the other, 

then the default apportionment of net generation to each of the units could be problematic. 

Therefore, as mentioned in the preamble to the proposal, the EPA intends to allow owners and 

operators of affected EGUs to propose alternative apportionment procedures for the EPA 

approval given unique plant configurations. The EPA welcomes comment regarding this default 

apportionment procedure. 

Monitoring of Non-electric Output at CHP units 

For affected EGUs that are combined heat and power (CHP) units (also known as 

cogeneration units), the combustion of fuel is used to provide both electric generation and other 

useful energy. Commonly, waste heat is captured and useful thermal output is provided for onsite use or sale. Thermal energy from CHP units can be used in direct process applications or 

indirectly to produce steam, hot water, hot air for drying, or chilled water for process cooling. 

Under the proposed rule, a CHP unit would demonstrate compliance with a rate based system on 

a net energy output basis: both net electric output and useful thermal output (converted into 
6

MWh equivalent) would be combined into net energy output. Therefore, for CHP units to 

demonstrate compliance with a rate based standard, the measurement of both net electric output 

and useful thermal output would be required. Mechanical energy from turbines can be used to 

drive rotating equipment, such as compressors, pumps and fans, and the exhaust of which may be 

routed through a heat recovery steam generator to generate electricity. Combustion turbines used 

for mechanical drive applications are typically used in the oil and gas industry. There may be a 

few such systems that meet the applicability requirements of the rule that would need to measure 

mechanical energy produced for net energy output. The EPA is seeking comment regarding the 

equipment used to measure and record mechanical output on an hourly basis for reporting 

purposes. 

The measurement of useful thermal output in the form of steam involves the monitoring 

of steam pressure and steam flow (and in the case of superheated steam, steam temperature). 

However, there are several potential methods depending on whether the heat content of 

condensate or steam return is measured and other considerations. Please refer to “Developing 

and Updating Output-Based NOx Allowance Allocations: Guidance for States Joining the NOx

Budget Trading Program under the NOx SIP Call”1 for more details, specifically section VI: 

Monitoring locations: Where could facilities monitor electric and thermal output and subsection 

D. How could sources monitor electric and thermal output at a cogeneration facility. The EPA 

presumes that a CHP unit that sells useful thermal output would already be using equipment to 

measure the saleable product. The operation and calibration equipment that measure pressure, 

temperate and steam flow leaving the unit and that measure the temperate and flow or returning 

condensate or the pressure, temperature and steam flow of returning steam would be needed. The 

EPA is seeking comment on the best practices for the measurement and recording of useful 

thermal output and the best practices regarding quality assurance protocols for such equipment. 

Reporting of Net Electric Generation and CHP Net Energy Output 

In order to facilitate compliance with a rate based standard, The EPA is proposing that an 

affected EGU could report hourly net electric generation under 40 CFR Part 75 via ECMPS, 

which would be included in emissions reports submitted quarterly. A CHP unit would 

                                                            

1 http://www.epa.gov/airmarkets/progsregs/nox/docs/finaloutputguidanc.pdf
7

additionally report net energy output as calculated from net electric generation, useful thermal 

output and any other useful mechanical output. Even if a rate based standard is based on gross 

electric output (rather than net), then an affected EGU would need to report gross electric output, 

and if a CHP unit, would need to also report energy output considering useful thermal output.

Reporting of Monitoring Plan Data and Quality Assurance Testing Data 

The EPA is seeking comment about including equipment used to measure net electric 

output (and net energy output for CHP units) in an EGU’s monitoring plan under 40 CFR Part 

75, as currently being reported via ECMPS. The EPA is also seeking comment on the reporting 

of the performance of tests on equipment used to measure net electric generation and net energy 

output for the purpose of determining whether the equipment is accurate or is operating as 

designed. Even if a rate based standard is based on gross electric output (rather than net), then 

monitor plan and quality assurance information would need to be submitted. The EPA invites 

comments regarding the quality assurance testing data that would be useful for reporting.