BOSTON (CBS) — Boston-based energy efficiency company Next Step Living abruptly closed its doors without warning on Friday.

The sudden development came as a surprise to utility companies, who had partnered with Next Step Living for work on the enormous statewide Mass Save program. The announcement also leaves approximately 2,000 MassSave customers in limbo, WBZ has learned.

In February, an I-Team investigation revealed horror stories from homeowners who had energy improvements performed by Next Step Living, along with dozens of complaints filed with the Attorney General’s Office, and hundreds of negative online reviews on sites like Yelp.

Next Step Living has not provided any explanation for the closure, but a statement on its web site confirmed the news.

“After 8 years, and tens of thousands of customers served, we are incredibly grateful to all of our team members, customers, partners, and investors who helped us along the way,” the statement said. “As mission-driven people who wanted to positively impact our community and plant, we wish we could have done more and done better by all parties.”

Recently named one of the fastest-growing companies in the state, Next Step Living once boasted more than 800 employees and $100 million in annual revenue.

However, industry reports suggest the firm had dropped down to 200 employees and run out of cash after investors pulled away support.

Utility companies like Eversource and National Grid are now scrambling to identify affected Mass Save customers and help them find other vendors to complete work. All contracts and deposits will be honored, the utilities tell the I-Team.

Approximately 700 customers had signed up for home energy assessments with Next Step Living. Another 1,300 homeowners had scheduled weatherization work with the shuttered company.

Medford resident Erika DeRoche learned of the closure on Friday when subcontractors performing insulation work had to stop in the middle of the project.

“It’s been a frustrating process,” DeRoche said. “The project management had already left a lot to be desired. I’m kicking myself for not doing more online research about the company.”

Newton homeowner Kyle Marchesseault said he had a good experience with his home energy assessment. He had already paid Next Step Living a $500 deposit and had secured a loan for thousands of dollars of insulation work to be completed in April.

“I was a little bit shocked, frustrated and surprised when I heard the news,” he said. “I have to figure out who is going to get this work done now.”

National Grid and Eversource have set up a toll free number for affected customers to ask questions: 877-315-1941.

“We will also be reaching out to them to discuss their options,” Eversource spokesman Mike Durand told the I-Team.

Next Step Living had also partnered with several local governments around the Boston area to promote energy improvements.

In October, the company signed an agreement with the City of Newton with the goal of achieving 1,000 home energy assessments in a year.

“I was very satisfied with their work,” Director of Sustainability Andrew Savitz said. “I am now looking for a backup vendor who can keep that momentum going.”

In the I-Team’s February report, the utility companies acknowledged they were aware of customer issues with Next Step Living. They told WBZ they had increased inspections and demanded improvements from company leaders.

On Friday, a spokeswoman with the Attorney General’s Office said 44 consumer complaints have been received.

Ryan Kath can be reached at rkath@cbs.com. You can follow him on Twitter or connect on Facebook.