A residential oil tank typically has a 275- or 330-gallon capacity. A double-wall heating oil tank with a steel exterior and a plastic interior lining to prevent oil leakage typically holds 160, 275 or 400 gallons. Tank capacities vary from region to region throughout the country.
Standard sizes for residential in-ground tanks in the Oregon region include 288, 340, 420, 518 and 555 gallons. Many Portland-area homes have 675-gallon capacity tanks. Usually, the price of oil per gallon decreases as the amount of oil the homeowner purchases at one time increases. A homeowner can fill the tank, decide on a specific amount of money to spend on oil, or order a certain number of gallons.