Pepco vigorously defended itself Monday in its first self-assessments since last month’s derecho storm, saying it responded aggressively and effectively to restore power to nearly half a million customers left sweltering in the dark.

The electric company accepted limited responsibility for software glitches that affected tens of thousands of calls for service and for its inability to give customers a better sense of when their power would be restored. But it asserted in the reports, required by Maryland and District regulators, that those issues are common in utilities across the country.

In addition, Pepco argued that it moved more quickly than other utilities to restore power after the violent June 29 storm.

“Unlike hurricanes that are tracked for days in advance, [Pepco] had little advanced warning to pre-position assets prior to the storm,” said the self-evaluation sent to Maryland regulators. “Pepco restored power as quickly as possible, particularly given the sheer number of outages. . . . Pepco mobilized quickly, calling on both internal and external resources to respond to the storm.”

The reports offered a look inside the company’s response to what it said was the most destructive storm for its network of power lines since Hurricane Isabel in 2003.

But they also ignited a new round of criticism that the utility is tone-deaf to complaints from customers and politicians.

“It’s more excuse-making. They are like the failing student that blames the teacher, the course and the books — everyone but themselves,” said Del. Tom Hucker (D-Montgomery). “The problem is not the system or the expectations of customers. The problem is Pepco.”

Del. Sam Arora (D-Montgomery) said the utility’s self-assessment was “overly rosy.”

“I suppose that is to be expected when you ask a company to grade itself,” he said. “This is like asking your child how he did in school before a bad report card hits your mailbox.”

A series of protracted Pepco outages dating to “Snowmaggedon” in 2010 as well as reports of poor reliability have put the company’s performance in the crosshairs of regulators.

In December, Maryland’s Public Service Commission levied a $1 million fine, its largest in recent memory, against Pepco for failing to keep up with tree-trimming and other preventive maintenance that could limit power disruptions due to storm damage.

In the aftermath of the June storm, unreturned calls or ones directed to automated answering services, along with conflicting reports about the timeline for power restoration, were at the heart of consumer complaints.

Hundreds of thousands of people in and around Washington fled or hunkered down in sweltering, darkened homes with no idea when the lights — and, more important, the air conditioning — might return.

Similar reports made public Monday by other utilities in Maryland show that Pepco customers were not alone in their misery. In the District and in Maryland, Pepco had a total of 483,639 customers without power at the peak of the outage. Baltimore Gas and Electric, which serves Baltimore and its suburbs, had 429,841 customers affected.

According to the reports, Pepco had all its customers back online by 4:30 a.m. on July 8, more than a week after the storm. BGE had full restoration at 2 p.m. that day. The average outage time for Pepco customers was about 26 hours; for BGE customers, it was 37.5 hours.

But Pepco customers who turn to the report for explanations about why the estimated times for the return of service were broad, or for why they sat in the dark as the company reported that their neighborhoods were back online, may be disappointed.

As with past storm reviews, Pepco acknowledged that it needs to improve its method for estimating restoration times.

The company said that it “very much recognizes that significant additional work remains to be done” to provide customers with more precise estimates of when their power will return.

On July 1, about 36 hours after the storm, Pepco gave what it called a “global estimate,” saying most customers would have power back by 11 p.m. on July 6.

The company reported that it beat that broad estimate for its customers in the District and in Montgomery and Prince George’s counties. But as it refined the estimates as damage reports came in, Pepco told some Montgomery County customers that they would probably be in the dark until July 8 — which also proved true.

Pepco said that it is working with a group set up by state regulators to improve its process but that delays in getting specific information to small clusters of customers happen because it waits for damage reports from on-site crews. That lag was also criticized in a 2011 report to Maryland regulators from a consultant hired to assess Pepco’s reliability issues.

Making up about half of the reports given to regulators Monday are news releases and company statements issued during the storm, presented to illustrate how Pepco communicated with government officials and the public.

About a dozen pages are filled with weather reports and maps showing the progression and intensity of the storm as it reached the Washington area.

In anticipation of outages from the heat wave, Pepco said, it had prepared to have 450 employees and contract workers on call. In the ensuing hours, however, the company was inundated with 7,446 calls about downed power lines.

It requested thousands of additional workers, but because of severe outages in neighboring areas, it took days for an additional 1,200 utility workers and hundreds of trucks to arrive, mostly from Florida and Georgia.

The morning after the storm, June 30, Pepco had 58 damage assessors, 335 line workers, 220 tree trimmers and 115 support workers responding to the storm. By July 3, that grew to 172 damage assessors, 1,411 line workers, 451 tree trimmers and 551 support personnel.

In Maryland, Pepco said, it prioritized restoring power to six hospitals, 106 nursing homes, the National Institutes of Health and 16 schools, including one elder-care facility in Montgomery that required the work of 50 crew members and 26 trucks for two days.

In all, Pepco’s 534,601 Maryland customers experienced a total of 786,766 sustained interruptions.

In the first three days after the storm, Pepco’s Web site received 108 million hits, more than in the first five months of the year combined. More than 54,000 people downloaded the company’s mobile app — nearly three times as many as had before — and used their phones 500,000 times to find out about the status of the power at their homes.

Victor Zapana contributed to this report.