Gasoline generator – Hours of operation

Download the gasoline generator operating hours calculator to help you estimate releases of National Pollutant Release Inventory (NPRI) substances.

Gasoline-powered reciprocating engine generators release criteria air contaminants (Part 4 substances). This release calculator uses default emission factors and can be adapted to use site-specific emission factors. If you want to use a site-specific emission factor, enter it in the emission factor column, but be sure to convert the units correctly. 

The spreadsheet calculators use emission factors based on uncontrolled emission sources. If you use an emission control device and the default emission factor is uncontrolled, use this formula to adjust the spreadsheet calculation:

Controlled emissions = uncontrolled emission x ((100 - control efficiency)/100)

Since NPRI reporting thresholds are for the facility as a whole, you may need to combine the air releases you calculate with releases from other sources at your facility.

The following sections explain how the spreadsheet calculator works.

Suggested estimation methodology: emission factor

The equation for estimation using an emission factor is:

E = (A x B x EF)/1000


  • E = emissions [tonnes]
  • A = hours of operation [hr]
  • B = operation horsepower [hp]
  • EF = emissions factor [kilograms (kg)/hp-hr]

Substance releases

Part 4 criteria air contaminants (CAC) releases
Substance Chemical Abstracts Service registry number (CAS RN)1 Emission factor (EF)2 EF units
Carbon monoxide (CO) 630-08-0 3.157E-03**  kg/hp - hour
Sulphur dioxide (SO2) 7446-09-5 2.681E-04 kg/hp - hour
Oxides of nitrogen (NOx), expressed as nitrogen dioxide (NO2) 11104-93-1 4.99E-03 kg/hp - hour
Total particulate matter (TPM) * 3.27E-04 kg/hp - hour
Particulate matter less than or equal to 10 micrometers (µm) (PM10) * 3.27E-04 kg/hp - hour
Particulate matter less than or equal to 2.5 µm (PM2.5) * 3.27E-04 kg/hp - hour
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