Central Maine Power has known for months that its new billing software was rife with problems, raising questions about its assertion in April that its software has nothing to do with why hundreds of customers have had unusually high bills over the winter.

More than 250 pages of documents filed at the Maine Public Utilities Commission show persistent problems with CMP’s new billing system, a situation that was downplayed by a top manager who in early April said the new billing system was not contributing to extraordinarily high bills for some 1,500 customers.

According to the internal documents, CMP was beset with problems when it switched over from its 27-year-old mainframe computer system on Oct. 30, 2017 — the day a powerful windstorm that knocked power out to more than 400,000 CMP customers. The problems included:

• Customers who paid their bills with an auto-pay feature were being de-enrolled.

• Some customers saw double usage on their bills, but zero cost.

• Some so-called net energy accounts, such as customers with solar panels, had very high estimated bills.

• SimplePay customers, who pay the same amount over the year to smooth out their bills, were dropped for minimal non-payment.

• Bills couldn’t be seen on iPhones.

The documents also show that staff from CMP and companies affiliated with Avangrid, CMP’s parent company, worked diligently, racking up overtime and weekends, to track down complex software errors.

This is a copy of an email warning that the billing problems could lead to an investigation.

A Jan. 15 email, from Susan Clary, CMP’s director of electric supply, to Rachel Grenier, who heads customer services, and other managers, discusses the topic of enrollment errors and supplier complaints stemming from electronic data exchange glitches in November and December.

“The company needs to get a handle on these and other issues soon or we will find ourselves in the middle of a Commission investigation,” Clary wrote.

She went on to say that CMP was aware that, “some customers are calling to complain that we are not billing the correct supplier rate or with the correct supplier.”

In February, according to a confidential Avangrid presentation, managers tried to figure out how to bring enough resources to bear to handle the billing system problems, as well as issues with customer service functions, meter reading and finance and accounting.

“At the current level of customer billing staff proficiency and productivity,” the presentation stated, “the resources are unavailable to effectively work backlog and keep up with normal volume of daily billing exceptions, even with help from other areas of Avangrid.”

The presentation noted that through the end of January, the company had carried out “35 fixes to bill print programs to reduce out of balance bills.”

The glitches had resulted in delayed billing to customers, high call volumes and long wait times and increased complaints to the PUC, it noted.

The presentation also mentions Avangrid’s relationship with the Deloitte consulting firm. It makes reference to a $266,700 contract and 9,920 hours of work over four months. It adds: “In the spirit of solidifying our relationship, Deloitte is offering an investment of more than 2,300 hours.”

These exchanges between CMP employees call into question the assertions made last month by CMP’s top management that an internal audit of more than 1,500 customer complaints found no problems with the company’s systems that would explain unusually high electric bills.

The company says it had reviewed about 25 percent of the 1,580 complaints of excessive bills it received this winter.

Auditors have so far found no anomalies in the company’s new billing software or its smart meter network to explain bills that for some customers were two to three times what they had been during the same period in the previous year, CMP President and CEO Doug Herling said in a conference call with reporters on April 5.

“We have done our investigation, at this point in time we have not found anything about our system or smart meters that would artificially increase customers’ usage,” he said.

The new documents are being circulated as the PUC is poised to hire at least one consultant with the experience to conduct what’s called a forensic audit – a comprehensive, technical examination of CMP’s meter and billing and systems. Work is scheduled to begin May 15, and wrap up no later than Dec. 31.

Hundreds of CMP customers are in an uproar over unusually high bills that have been coming in since November. Some people say their bills have more than doubled or tripled and they’re not convinced by explanations that CMP’s changeover to a new billing system, the early winter cold spell and an 18 percent hike in standard-offer electric rates in January combined to cause the spike.

The PUC’s staff also has been conducting a data-request audit with CMP, searching for answers.