ANDOVER — Energy efficiency is a priority in the town's 10 school buildings. At West Elementary School, the quest for lower utility bills was given as a homework assignment this fall.

Under a program sponsored by National Grid, students were asked to survey their families' household energy consumption.

They monitored the use of electronics, checked for drafts and gaps in insulation, and asked their parents if they considered energy efficiency while shopping for major appliances.

Students also made poster projects about topics related to energy and the environment.

On Thursday, parents will be invited to Go Green Night at the school, where they can see the posters and enter to win a raffle for compound fluorescent light bulbs.

The best posters, as judged by a panel, were made by first-graders Kiana Park and Jenna Freeland, third-graders Colin Elmer and Katelyn Tsai, and fifth-grader Gillian Cowe.

Today, the five students will receive tickets to Halloween Town at the Seaport World Trade Center in Boston, which is also a stop on the Energy Star Home Exhibit Tour on Saturday and Sunday.

West Elementary is one of just five schools in Massachusetts and Rhode Island participating in National Grid's Power to Save program.

The program is part of the utility company's Whole Building Assessment Initiative.

National Grid has performed energy audits at all of Andover's 10 schools in recent years. The town has reduced its annual electrical bill by more than $100,000 by upgrading to energy-efficient lighting.

At West Elementary, heating and lighting in the building is controlled through a townwide energy management system. Boilers have been upgraded to burn natural gas and the new roof is heavily insulated.

Principal Elizabeth Roos said students at West Elementary have enjoyed learning about energy efficiency. They also reinforce the importance of going green to their parents and teachers, she said.

"They're bringing adults on board," Roos said. "The kids are the ones who are really going to make it happen."