Use a chart to determine the energy content of a barrel of crude oil, such as provided in the Resources. In this case, the chart claims one barrel will produce 6.1x10^9 joules (6,100,000,000 joules).
Multiply 6.1x10^9 joules by the number of barrels to be converted. For example, 3 barrels of oil = 3 x 6.1x10^9 joules/barrel = 1.83x10^10 joules.
Divide the number from Step 2 by 3.6110^6 to convert joules to kilowatt-hours. For example, 1.83x10^10 / 3.6110^6 = approximately 8,254,412 kw-h.
Multiply the kilowatt-hours by 1,000 to convert to Megawatt-hours. For example, (8.25x10^6 kw-h) x 1,000 = approximately 8.25x10^9 Mw-h.
Open an online conversion tool.
Choose the "Energy" conversion list.
Select "fuel oil equivalent @barrel (US)" under "Convert From."
Select "megawatt-hour" under "Convert To."
Enter the number of barrels to convert. Press "Enter." The conversion is displayed.