Residential water heating accounts for 3% of all US greenhouse gas emissions and 19% of home energy use, which means it uses a large chunk of a home's energy while adding emissions to our environment. An intelligent heat pump-based water heater is a step in the right direction on both fronts. In this episode of Hardware to Save a Planet, Dylan talks with Michael Rigney, CEO and co-founder of Cala Systems, about their innovative heat pump water heater. They delve into the environmental impact of residential water heating and the need for sustainable solutions. They also discuss the challenges of finding a job at the intersection of hard tech and climate and how the current climate tech wave has opened up more opportunities in this field. Michael highlights the importance of shifting when energy is used and the advantages of using thermal energy storage in water heaters. They discuss the key components of a water heater and how Cala Systems has optimized its system for comfort, cost, and carbon emissions. He emphasizes their goal of providing helpful intelligence for homeowners. The conversation also touches on the challenges faced during hardware development and the potential for Ka water heaters to participate in demand response programs.