Residential solar-panel installer Sunrun Inc. /zigman2/quotes/205021014/composite RUN -2.61% announced a deal Monday night to acquire rival Vivint Solar Inc. /zigman2/quotes/202100570/composite VSLR -2.05% for about $3.2 billion, including debt. In a statement, the companies said Vivint shareholders would get 0.55 shares of Sunrun for every share held, leaving Vivint shareholders with about a 36% stake in the combined company. The merger will deliver an annual cost savings of about $90 million, the companies said. "Vivint Solar adds an important and high-quality sales channel that enables our combined company to reach more households and raise awareness about the benefits of home solar and batteries," Lynn Jurich, Sunrun's chief executive and co-founder, said in a statement. "This transaction will increase our scale and grow our energy services network to help replace centralized, polluting power plants and accelerate the transition to a 100% clean energy future." Sunrun shares have gained 55% year to date, while Vivint has risen 46%, compared to the S&P 500's /zigman2/quotes/210599714/realtime SPX -2.27% 1.6% decline this year.