The Longwood Software Inc., headquarters at 107 Main St. has become the town’s first commercial building to install a solar energy system. The solar project was initiated by the software company to provide clean, cost-effective energy for its office and staff, according to an announcement. The system, installed by Mass Renewables and made by the Lawrence-based company Solectria Renewables, is a 5-kilowatt system consisting of 20 power-generating panels. “Our solar energy system is good for our company and for the environment,” said Scott Richardson, president of Longwood Software in the news release. In November, Massachusetts was named the most energy efficient state in the country by the American Council for an Energy-Efficient Economy in its annual scorecard. - Derek McLean