A severe storm passed through Joliet earlier this week, leaving thousands without power.
The power outage took 16 units offline on Monday night, according to data from IIR.
Among them are a 127,000-barrels-per-calendar-day (bcd) vacuum distillation unit and a 98,000-bcd fluid catalytic cracker unit. Four hydrotreater units and three sulfur recovery units also went down during the outage.
The units are expected to be down for a week with plans to restart over the upcoming weekend, according to IIR.
Exxon did not immediately respond to a request for comment.
The outage sparked panic buying in the Chicago wholesale market, pushing prices higher for refined products in the region. Chicago diesel traded at a discount of 2.50 cents against the ultra-low sulfur diesel futures benchmark on Wednesday, 15.25 cents higher than Tuesday.
