Satisfaction among Pepco customers plummeted in the first quarter, putting it at the bottom of the 25 largest investor-owned energy utilities when it comes to keeping bill payers happy, according to a report scheduled for release Tuesday.

The annual survey was conducted by the American Customer Satisfaction Index, an Ann Arbor, Mich.-based organization that surveys satisfaction among a range of major industries and business sectors.

On a scale that goes from zero to 100, Pepco’s score fell to 54 from 70 in the first quarter of 2010, the report says. Pepco’s score had been falling slightly during most of the past seven years, according to the report, but never so steeply.

“Overall, utilities had a brutal winter, but [Pepco’s score] reflects that . . . other utilities didn’t struggle as much as Pepco did to get power back on and to respond to customers,” said David VanAmburg, managing director of ASCI.

The average score for the energy utilities in the survey was 75.

In a written response, Pepco spokesman Bob Hainey said: “We recognize the frustration that our customers have experienced over the last several months. That is why Pepco is collaborating with all relevant stakeholders to improve our service.

“To that end, our responses to recent storms, such as the violent thunderstorm on Saturday, have shown substantial improvement.”

Only two other utilities since 2000 have experienced so sharp a decline in customer satisfaction, VanAmburg said: Pacific Gas & Electric in California, whose scores dropped in 2001 after brown-outs, and Ameren, an electricity and natural gas provider in Missouri and Illinois that saw a big decline in 2007 after its response to a series of storms.

It took both utilities years to regain anything close to their previous customer satisfaction levels, the report shows.

The report was based on telephone interviews with 250 customers of each utility in the report, said VanAmburg.

The report comes a week after Maryland legislators passed a bill that imposes a $25,000-a-day fine on electric utilities for each violation of reliability standards. Those standards will involve how often power goes out, how long it stays out and a company’s response to customer calls, among other items. The exact standards still have to be drafted. They are to be enforced by July 2013.

Legislators passed the bill following public outcry over sustained Pepco outages last winter. The bill raises the maximum daily fine per lapse to $25,000 from $10,000 and specifies that utilities may not recover the cost of fines from ratepayers.

In March, utility regulators in the District separately proposed rules that would impose financial penalties on Pepco if it failed to meet new reliability standards and move into the ranks of top-performing utilities nationwide by 2020.

Pepco has about 778,000 residential and commercial customers in the District and Montgomery and Prince George’s counties.

A Washington Post investigation published in December found that Pepco’s customers in Maryland had substantially more day-to-day power outages than its customers in the District. The newspaper’s study determined that reliability began declining five years ago and that Pepco ranks at or near the bottom in industry surveys of reliability. The investigation also found that Pepco suffered reliability problems even on days with no storms.

Pepco has launched an extensive plan to improve equipment, trim trees that can cause outages and enhance customer service. The company said in an April 14 statement that in the last six months, it had trimmed trees along 1,600 miles of power lines, invested in equipment to carry more load and reroute power more efficiently during storms to help restore power, and made other changes.