Sustainability has long been a major topic for data centers, which are among the world’s largest consumers of electricity. Optimizing power consumption and reducing carbon emissions are always top of mind for data center operators. So far, renewable energy procurement has been essential in allowing large cloud providers to run an almost entirely decarbonized infrastructure. The need for backup power systems, however, has made running a fully green operation elusive for many. The diesel genset — the most popular and robust backup power supply solution — is a double-edged sword. Though critical for ensuring operational continuity in data centers, their use means carbon emissions are unavoidable. At the beginning of 2020, initiatives around emission-free data centers were announced, pushing the industry to rethink the role of these stalwart systems.