In greenhouse gas inventories , energy audits , and the implementation of sustainable development goals, businesses frequently use two units of measurement: tCO₂e (tons of CO₂ equivalent) and TOE (tons of oil equivalent) .
Although both play important roles in the energy and environmental sectors, these two units reflect different quantities. Understanding the nature, calculation methods, and application scope of tCO₂e and TOE helps businesses effectively manage energy use, control greenhouse gas emissions, and develop appropriate emission reduction strategies.
1. What is tCO₂e?
tCO₂e (Tonnes of Carbon Dioxide Equivalent) is a unit of measurement for greenhouse gas emissions, converted to an equivalent amount of CO₂ that contributes to global warming.
Because greenhouse gases such as CO₂, CH₄, N₂O, and others have varying levels of impact on the climate, using tCO₂e helps to standardize the measurement, aggregation, and comparison of emissions.
The unit tCO₂e is commonly used in:
- Inventory and reporting of greenhouse gas emissions.
- Prepare ESG reports and sustainability reports.
- Assess your carbon footprint.
- Develop an emissions reduction strategy and a Net Zero roadmap.
- Activities related to the carbon market and carbon credits.
How to calculate tCO₂e
Greenhouse gas emissions are typically determined based on operational data, emission factors, and the global warming potential (GWP).
tCO₂e = ∑ (Emissions of each type of greenhouse gas × corresponding GWP)
In there:
- Operational data: Information on fuel consumption, electricity usage, transportation activity, or other emission sources.
- Emission factor: A factor that represents the amount of greenhouse gases produced per unit of activity.
- GWP (Global Warming Potential): A coefficient that expresses the potential of each greenhouse gas to contribute to global warming compared to CO₂ over a defined period of time.
The emissions of each gas can be calculated from operational data and appropriate emission factors, then converted to CO₂ equivalent. The final result is expressed in tCO₂e.
Legal basis in Vietnam
Greenhouse gas inventory activities in Vietnam are regulated and guided through a system of legal documents, including:
- Decree No. 06/2022/ND-CP on mitigating greenhouse gas emissions and protecting the ozone layer, amended and supplemented by Decree No. 119/2025/ND-CP .
- Circular No. 17/2022/TT-BTNMT stipulates the technical regulations for measuring, reporting, and assessing greenhouse gas emission reduction and greenhouse gas inventory in the waste management sector.
- Circular No. 38/2023/TT-BCT stipulates the technical regulations for measuring, reporting, assessing greenhouse gas emission reduction and greenhouse gas inventory in the Industry and Trade sector.
- Circular No. 13/2024/TT-BXD provides guidance on the method of greenhouse gas inventory and the measurement, reporting, and assessment of greenhouse gas emission reduction in the construction sector.
In addition, businesses need to use emission factors and calculation methods that are appropriate for each sector, emission source, and reporting period, in accordance with current regulations.
2. What is TOE?
TOE (Tonne of Oil Equivalent) , or ton of oil equivalent , is a unit of energy measurement used to convert various fuels and other forms of energy into a common unit.
Through TOE, businesses can aggregate energy consumption from multiple sources such as electricity, coal, oil, natural gas, and other fuels, facilitating the assessment and management of energy efficiency.
TOE is used in:
- Conduct an energy audit.
- Develop and operate an energy management system.
- Compile and report on energy usage.
- Identify and manage key energy-consuming facilities.
- Assess energy efficiency and identify energy saving potential.
How to calculate TOE
According to international convention:
1 TOE = 41,868 GJ ≈ 11,630 kWh
In practice, energy consumption is converted to TOE using the following formula:
TOE = Energy Consumption × TOE Conversion Factor
In there:
- Energy consumption: The amount or output of electricity or fuel used during the calculation period.
- TOE conversion factor: The conversion factor for converting each type of energy or fuel into its equivalent tons of oil.
TOE conversion factor in Vietnam
According to Official Letter No. 3505/BCT-KHCN dated April 19, 2011, from the Ministry of Industry and Trade regarding the compilation of a list of key energy-consuming facilities, some energy conversion coefficients are used as follows:
| Fuel/Energy Type | TOE conversion factor |
|---|---|
| Electricity | 0.1543 TOE/MWh |
| Anthracite coal | 0.7 TOE/ton |
| DO oil | 1.02 TOE/ton |
| Fuel oil | 0.98 TOE/ton |
| LPG | 1.13 TOE/ton |
| Natural gas | 0.9 TOE/1,000 m³ |
Note: The above coefficients are quoted from Official Letter No. 3505/BCT-KHCN . When preparing reports as required, businesses need to compare them with the conversion coefficients and guidelines in effect at the time of reporting.
Converting to TOE helps businesses standardize energy consumption data, thereby identifying high-energy-consuming areas, evaluating operational efficiency, and proposing appropriate energy-saving solutions.
3. The difference between tCO₂e and TOE
Although both are used in energy and environmental management, tCO₂e and TOE differ in nature, purpose, and calculation methods.
| Criteria | tCO₂e | TOE |
|---|---|---|
| Nature | Units of measurement for greenhouse gas equivalents | Unit of energy conversion |
| Name | Tons of CO₂ equivalent | Tons of oil equivalent |
| Purpose | Measuring and managing greenhouse gas emissions. | Measuring and managing energy consumption. |
| Application | Greenhouse gas inventory, ESG, Net Zero | Energy audit, energy management |
| Computational basis | Emission factor and GWP | Heat value and energy conversion factor |
| The results reflect | Emission levels and their impact on climate change | Scale of energy consumption |
Simply put:
- TOE indicates how much energy a business consumes.
- tCO₂e indicates the amount of greenhouse gases generated from a business’s operations, after being converted to CO₂ equivalent.
These two indicators provide complementary perspectives, helping businesses simultaneously assess energy efficiency and greenhouse gas emissions.
4. Can TOE be directly converted to tCO₂e?
TOE cannot be directly converted to tCO₂e using a fixed coefficient that applies universally to all cases.
The reason is that TOE reflects the amount of energy consumed, while tCO₂e depends on the characteristics of the energy source and the amount of greenhouse gases generated during use.
For example, with the same energy consumption in TOE, using coal, oil, or natural gas can generate different greenhouse gas emissions due to the respective fuel characteristics and emission factors.
To determine emissions from energy consumption data, businesses need to:
- Identify the type of fuel or energy source being used.
- Collect actual energy consumption data.
- Choose the appropriate emission factor for each source.
- Calculate and convert greenhouse gas emissions to tCO₂e.
Thus, TOE can be used as input data for emission calculations, but it cannot replace tCO₂e in greenhouse gas inventory operations.
5. Conclusion
tCO₂e and TOE are two important units of measurement, serving different but closely related purposes in energy and environmental management.
While TOE helps businesses monitor consumption and assess energy efficiency, tCO₂e is the basis for measuring, controlling, and developing solutions to reduce greenhouse gas emissions.
Proper understanding and appropriate use of these two indicators not only improves the quality of management data but also supports businesses in effectively implementing energy audits, greenhouse gas inventories, ESG reporting, and gradually moving towards sustainable development goals.
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