Stem built its business on the idea that energy storage only reaches its full potential when paired with smart software. Founded in 2009 in San Francisco, the company developed Athena — an AI platform that controls battery storage systems to reduce energy costs, participate in grid services markets, and maximize the value of solar-plus-storage installations.
Athena manages over 30 GWh of storage and solar assets under management, making it one of the largest digitally connected energy storage networks in the world. The platform monitors real-time electricity prices, demand charges, weather conditions, and grid signals to decide when batteries should charge or discharge. For commercial building owners, this often means significant cuts to peak demand charges on their utility bills. For utility-scale operators, Athena optimizes revenue from energy arbitrage, frequency regulation, and capacity market participation.
Stem went public through a SPAC merger in 2021 and expanded aggressively through acquisitions, including AlsoEnergy (a solar monitoring platform) and other technology companies. Revenue reached the hundreds of millions, but rapid expansion and integration challenges put pressure on margins. In late 2024, Stem agreed to be acquired by AlphaESS, a global energy storage company, in a deal aimed at combining hardware manufacturing with Stem’s software capabilities. The company has approximately 800 employees. Stem’s trajectory illustrates both the massive opportunity in energy storage software and the difficulty of scaling a capital-intensive business in a fast-evolving market.
