GREENFIELD — A mailing was sent in error to approximately 700 homes last week, to residents who do not currently subscribe to Greenfield Light & Power, due to a mistake on the part of the city’s supplier.

This mailing was part of a routine mailing to new electric accounts as part of the “opt-out” for Greenfield Light & Power. Residents who had opted out of the program when it was first launched years ago were not removed from the list, and received the opt-out letter again erroneously. The city apologized in a statement posted on its website.

According to Carole Collins, Greenfield’s director of energy and sustainability for the city, “We are still trying to get to the bottom of what exactly happened, and we will not enroll anyone who received this letter in error. Please accept my sincere apologies for the confusion.”

Greenfield Light & Power is a municipal aggregation under Massachusetts General Law and approved by the Department of Public Utilities. There are approximately 150 aggregations in Massachusetts, according to Greenfield’s website.

Per the state, customer participation is voluntary. The town provides customers with an opportunity to opt-out of participating. Customers who do not opt out will be automatically enrolled in the aggregation program, but may opt out at any time after that.

Any Greenfield electricity customer may join or leave the program at any time by calling 1-866-968-8065.

Greenfield Light & Power is designed to make 100 percent renewable energy available to city residents and businesses, the Greenfield website states. For the last three years, it has offered residents a savings over Eversource’s basic services and has saved Greenfield subscribers more than $1 million dollars, though Eversource’s prices change every six months and a savings cannot be guaranteed. Currently, Greenfield Light & Power’s program price is fixed until January 2021.

“We are tireless advocates protecting the most vulnerable in our community who are targeted by predatory suppliers,” Collins said. “And we have filed several complaints with the attorney general’s office on behalf of Greenfield residents. Just last week, our office helped a resident who had been unknowingly switched to a third party supplier and was paying in excess of 16 cents per kilowatt-hour.”

Reach Melina Bourdeau at 413-772-0261, ext. 263 or mbourdeau@recorder.com.