Natural gas and propane differ in CO₂ output, cost, storage, and infrastructure. The current EIA CO₂ coefficient table lists natural gas at 116.65 lb CO₂ per million BTU and propane at 138.63 lb CO₂ per million BTU. That makes natural gas lower on a gross heat-input basis.
That simple comparison is not a permit calculation. NOx, SOx, PM, CO, VOC, CH₄, N₂O, controls, equipment class, sulfur content, supplier heat content, source-test data, CEMS data, and reporting method can change the answer for regulated use.
CO₂ Coefficients and Calculation Method
The source-aware app uses EIA CO₂ rows: natural gas at 116.65 lb CO₂ per million BTU and propane at 138.63 lb CO₂ per million BTU. Natural gas is about 15.9% lower than propane when the comparison is expressed as propane-minus-gas divided by propane.
A facility burning 50,000 therms of natural gas per year produces about 583,250 lb CO₂ using that EIA row. The same gross heat input from propane produces about 693,150 lb CO₂. Those are screening numbers only.
For greenhouse gas reporting, check the current EPA GHG factors or 40 CFR Part 98 method. CH₄, N₂O, GWP basis, reporting year, default high heat value, fuel records, and program instructions may be required.
Natural gas: Therms × 0.1 × 116.65 = lb CO₂
Propane: Gallons × 0.0915 × 138.63 = lb CO₂
Quick factors: 1 therm NG = 11.665 lb CO₂
1 gallon propane = about 12.69 lb CO₂
Natural Gas vs Propane Emissions Calculator
Compare CO2, NOx, and total emissions between natural gas and propane for heating and process applications. See emissions per MMBtu delivered and annual totals based on your usage.
Cost Per Million BTU Comparison
Cost comparison still needs a common heat basis. Natural gas at $1.20 per therm is $12.00 per million BTU before equipment losses. Propane at $2.50 per gallon and 91,500 BTU per gallon is about $27.32 per million BTU before equipment losses.
Equipment efficiency is not guaranteed to be identical. Use the actual AFUE, combustion test, manufacturer data, or project model for the installed equipment. The app uses AFUE only to screen delivered heat and CO₂ per delivered MMBtu.
Fuel switching economics also need conversion parts, labor, controls, tanks, utility extension, downtime, service availability, and contract terms. The emissions screen does not calculate those costs.
Infrastructure and Conversion Considerations
The biggest factor is often infrastructure availability. Natural gas service may require utility extension, meter capacity, pressure review, code approval, and gas-piping work. Propane requires on-site tank storage, delivery access, regulator layout, supplier terms, and LP-gas code review.
Equipment conversion between fuels requires manufacturer-approved parts and setup. Orifice size, manifold pressure, combustion-air setup, venting, controls, listing limits, and commissioning all matter.
Treat any cost ranges as local bid items, not universal pricing. Ask the gas utility, propane supplier, HVAC contractor, and permitting authority for project-specific requirements.