What Is TEP (Tonne of Oil Equivalent)? How to Calculate It

In short: TEP (Turkish abbreviation for tonne of oil equivalent, toe) is an energy unit used to add up different energy sources in one number: 1 TEP = 10 million kcal = 41.868 GJ = 11,630 kWh. In Turkey, TEP is calculated by multiplying the annual quantity of each fuel and of electricity by the conversion factor of the Ministry of Energy and Natural Resources and summing the results; for example, 1 MWh of electricity counts as 0.086 TEP and 1,000 m³ of natural gas as 0.825 TEP.

What is TEP and why is it used?

A facility buys electricity in kWh, natural gas in Sm³, diesel in litres or tonnes and coal in tonnes. These units cannot be added directly. TEP converts all of them to a common denominator: "equivalent to the heat energy of one tonne of crude oil". In international literature the same unit is called toe (tonne of oil equivalent); according to the International Energy Agency (IEA) and OECD definition, 1 toe = 41.868 GJ, i.e. exactly 11.63 MWh.

In Turkey, TEP matters legally: Energy Efficiency Law No. 5627 (Official Gazette 02.05.2007) and the Regulation on Increasing Efficiency in the Use of Energy Resources and Energy based on it (Official Gazette 27.10.2011, last amended 21.09.2024) tie obligations such as appointing an energy manager, energy audits and ISO 50001 to a site's total annual energy consumption expressed in TEP. Getting TEP wrong can mean missing an obligation or taking one on unnecessarily.

• 1 TEP = 10,000,000 kcal (10⁷ kcal)
• 1 TEP = 41.868 GJ
• 1 TEP = 11,630 kWh = 11.63 MWh

Official TEP conversion factors

The original 2011 text of the regulation contained Annex 2, a table titled "Net Calorific Values of Energy Sources and Conversion Factors to Oil Equivalent". That annex was repealed by the amendment of 06.07.2022; Article 9 of the regulation now states that "the energy consumption calculation methodology used to determine the obligation status is published on the Ministry's website". The "TEP Conversion Table Calculation Tool" published on the Ministry's energy audit page uses the same net calorific values and factors (as of 2026). Frequently used items:

All factors in the table follow the same logic: net calorific value (kcal) ÷ 10,000,000. For natural gas, 8,250,000 kcal ÷ 10⁷ = 0.825 TEP. For a fuel not listed here (e.g. wood, petroleum coke, olive pomace), check the full table in the Ministry's tool; because the Ministry can update the official methodology, check the current version before reporting.

How to calculate TEP step by step

1. Define the period. Obligations are assessed on total annual consumption.
2. Add up the annual quantity of each source. Electricity bills or meter readings (kWh), the corrected volume on natural gas bills (Sm³), fuel purchase records (litres or tonnes).
3. Convert to the factor's unit. Electricity from kWh to MWh (÷1,000), natural gas from m³ to thousand m³ (÷1,000), liquid fuel from litres to tonnes (litres × density ÷ 1,000).
4. Multiply by the factor. TEP = quantity × conversion factor.
5. Sum all sources. The result is the site's total energy consumption for that year.

The regulation also requires looking at the average of the last three years each year. For newly established buildings and plants, if first-year consumption exceeds twice the threshold, the obligation applies without waiting for a three-year average.

Natural gas: Sm³, net and gross calorific value

Natural gas causes the most confusion in TEP calculations. According to the BOTAŞ (Turkish state gas pipeline company) definition, a standard cubic metre (Sm³) is the quantity of natural gas, free of water vapour, that fills 1 m³ at 15 °C and 1.01325 bar absolute pressure and has a gross calorific value of 9,155 kcal. The raw volume shown by the meter depends on line pressure and temperature; the distribution company converts it to standard conditions with a correction factor on the bill and turns it into kWh using the average gross calorific value.

The TEP table, however, uses the net calorific value for natural gas (8,250 kcal/m³). The gross value is higher because it also includes the condensation heat of the water vapour in the flue gas. The correct method is therefore to take the corrected volume (Sm³) from the bill and multiply it by 0.825 TEP per thousand m³. Multiplying the kWh figure on the gas bill by 0.086, as for electricity, overstates the result by roughly 10% because that figure is based on the gross calorific value. To track gas consumption monthly, see the natural gas monitoring page.

Worked example: electricity + natural gas + diesel

Assume a site's annual consumption is 6,000 MWh of electricity, 500,000 Sm³ of natural gas and 20 tonnes of diesel for generators.

Interpretation: if this site is an industrial plant, it is below 1,000 TEP this year; however, the decision is based on the three-year average and the threshold can easily be crossed with higher production. If the same consumption belongs to a commercial or service building (hotel, hospital, shopping mall), the 500 TEP threshold is clearly exceeded. For reference: 1,000 TEP equals about 11,630 MWh of electricity alone, or about 1.21 million Sm³ of natural gas alone.

What do the thresholds mean?

Under Articles 9 and 10 of the regulation (after the 06.07.2022 amendment, as of 2026) the main thresholds are:

• Industrial plants, 1,000 TEP and above: appoint a certified energy manager; energy audit every four years.
• Commercial and service buildings, 500 TEP and above or at least 20,000 m² floor area: energy manager; building audit every seven years.
• Public buildings, 250 TEP and above or at least 10,000 m²: energy manager; building audit every seven years.
• Non-public industrial plants, 50,000 TEP and above: establish an energy management unit.

Those obliged to appoint an energy manager must also implement and certify a TS EN ISO 50001 energy management system and report their energy consumption data to the Ministry by the end of March each year. Tracking the obligation is the management's own responsibility. For details see our article on the energy manager obligation, and for the system side the ISO 50001 energy management system guide.

Common mistakes

• Mixing up kWh and MWh: the 0.086 factor applies per 1,000 kWh (1 MWh). Multiplying 6,000,000 kWh directly by 0.086 gives 516,000 TEP, a result off by a factor of one thousand.
• Mixing up raw m³ and Sm³: on pressurised lines, the raw volume shown by the meter can differ significantly from the standard volume. Use the corrected volume on the bill.
• Multiplying the gas bill's kWh by 0.086: the bill's kWh is based on the gross calorific value, while the table uses the net value. The result is inflated by about 10%.
• Mixing up primary and final energy: the TEP table counts electricity as final energy at the point of use (860 kcal/kWh), not the fuel burned at the power plant. The primary energy factor used in building energy performance calculations (BEP-TR; 1.826 from 2021 onwards according to an announcement of the Ministry of Environment, Urbanisation and Climate Change) serves a different purpose and must not be mixed into the TEP threshold calculation.
• Looking at a single year: the obligation is determined by the average of the last three years.
• Forgetting small items: generator diesel, kitchen LPG and vehicle fuel can push the total over the threshold.
• Confusing TEP with carbon: TEP is an amount of energy; greenhouse gases require separate emission factors. See the carbon tracking page for that.

Practical checklist

• Collect the last three years of electricity, natural gas and fuel bills in one table.
• Record electricity in MWh, natural gas in corrected thousand Sm³ and liquid fuels in tonnes.
• Confirm the factors against the Ministry's current TEP tool.
• Calculate the annual totals and the three-year average; for buildings, also check the floor area threshold.
• If you are close to a threshold, monitor consumption monthly and see early which item is growing. For saving ideas, read how to save energy.

How does Argus EMS help with TEP calculation?

The quality of a TEP calculation depends on the quality of its input data. Argus EMS reads on-site meters and energy analysers over Modbus TCP/RTU and M-Bus through a Field Agent running on site and sends the data to the server over TLS-encrypted MQTT; when the connection drops, it buffers data locally and sends it later, preventing data loss.

• It monitors electricity, water, natural gas, UPS and generators on one platform, with hourly, daily and monthly consumption dashboards.
• For electricity it shows the T1/T2/T3 (day/peak/night) time-band breakdown and the reactive ratio, and sends e-mail alarms for reactive and threshold violations.
• It provides month-end consumption and cost projection with budget tracking, and shows multiple sites on one screen.
• Data export makes it easy to carry annual kWh and m³ totals straight into your TEP table.

For the full picture of measurement-based efficiency work, see our energy efficiency solution page.