How many standard cubic metres of natural gas does a gas engine or turbine need for one unit of electricity?

From the Petroleum Planning and Analysis Cell (PPAC) figure of 4,541 standard cubic metres (SCM) a day for 1 megawatt (MW) of generation, one kilowatt hour (kWh) takes about 0.189 SCM. A cross-check from PPAC's 1,720 kilocalorie (kcal) heat rate gives 0.191. A small engine below 50% efficiency needs more.

PPAC's inputs

• Table 9.5, Natural Gas Conversions, credits GAIL (India) Ltd. Gas required for 1 MW of power generation = 4,541 SCM per day, with a station heat rate of about 1,720 kcal per kWh on a net calorific value (NCV) basis, 50% thermal efficiency, and natural gas gross calorific value (GCV) of 10,000 kcal per SCM.
• The same table says power generation from 1 million SCM a day of gas is 220 MWH. 1,000,000 / 4,541 = 220.2, so I read the unit as megawatts, not megawatt hours. That reading is mine.

The arithmetic

1. 4,541 SCM per day / 24 hours = 189.2 SCM per hour for 1 MW, which is 1,000 kWh. So 0.1892 SCM per kWh.
2. Cross-check from the heat rate: PPAC's NCV is 90% of GCV, so 9,000 kcal per SCM. 1,720 / 9,000 = 0.1911 SCM per kWh.
3. The two differ by 1.0%. PPAC's 4,541 implies 24,000 x 1,720 / 4,541 = 9,090 kcal of net energy per SCM, slightly above the 90% rule. PPAC does not explain the gap.
4. At a lower efficiency, scale up: SCM per kWh = 0.1892 x (50% / your efficiency), using net-basis (lower heating value) efficiency, as PPAC's heat rate is net. Engine datasheets may quote gross, so check.

Check your own engine

• Divide the month's gas in SCM, from the meter feeding the engine, by the kWh on the engine's own meter. That is your real figure.
• A gas engine at 38% electrical efficiency needs 0.1892 x 50 / 38 = 0.249 SCM per kWh. At 35% it is 0.270.
• A reading well under 0.19 would mean better than 50% efficiency on PPAC's basis. For a small engine, treat that as a meter or units mistake until proved otherwise. This is my reading.
• If the gas meter also feeds a boiler, sub-meter the engine or the result is meaningless.

20,000 SCM of piped natural gas and 75,000 kWh in a month

• Your figure: 20,000 / 75,000 = 0.2667 SCM per kWh
• PPAC reference at 50%: 0.1892. Implied efficiency: 0.1892 / 0.2667 x 50% = 35.5%
• Carbon dioxide (CO2) at 2.05 kilograms (kg) per SCM: 0.2667 x 2.05 = 0.547 kg per kWh
• At PPAC's reference 0.1892 SCM per kWh the same factor gives 0.388 kg per kWh. At 2.12 kg per SCM, the PPAC-based figure from the other gas page, it gives 0.401. The gas power page on this site, which starts from PPAC's 1,720 kcal, says 404 g per kWh, so 0.401 against 0.404 differs only by route

The 2.05 and 2.12 kg per SCM are the two figures discussed on the natural gas calorific value page on this site, which explains why they differ by about 3%.

What Senseible does here

Senseible reads fuel invoices and electricity bills into monthly records, and keep both bills with the engine meter reading. The engine's own kWh meter reading is a separate number you will need to keep.

• Gas generator CO2 per kWh against diesel and grid
• Gas power CO2 at a 1,720 kcal heat rate
• India natural gas GCV per SCM
• Gas volume to energy: two conversions

Sources: PPAC Ready Reckoner 2025-26, Table 9.5 Natural Gas Conversions (gas required for 1 MW, heat rate, GCV and NCV)

Last reviewed 2026-11-05. PPAC's figures are for a 50% efficient plant. Use your engine maker's heat rate or your own meters for a real site.