Gross inputs to U.S. petroleum refineries, also referred to as refinery runs, hit the highest annual average on record in 2018, the U.S. Energy Information Administration (EIA) said on Tuesday.

U.S. refinery runs averaged 17.3 million barrels per day (b/d) in 2018, also the fifth consecutive year of refinery runs.

Refinery runs peaked in June at an average of 18.0 million b/d.

The record-high U.S. gross refinery input levels are mainly driven by refinery operations in the Gulf Coast and Midwest regions.

In the Gulf Coast, which is home to more than half of all U.S. refinery capacity, refinery runs averaged over 9.2 million b/d in 2018, or 8 percent higher than the previous five-year average for that region and the first time the annual average surpassed 9.0 million b/d.

The Midwest regions have the second-highest refinery capacity, and refinery runs averaged 3.8 million b/d in 2018, or 6 percent higher than the previous five-year average.

As a percentage of operable capacity, refinery utilization averaged 93.2 percent in 2018, an increase of about 2.1 percent from 2017, but still not surpassing the record of 95.6 percent set in 1998.

In the March update of its Short-Term Energy Outlook, EIA expected U.S. refinery runs in 2019 to be relatively flat compared with the record-high 2018 levels, partially as a result of expected high levels of refinery maintenance in 2019. Refinery runs in 2020 are expected to increase and reach a new record of 17.8 million b/d.