Recently, I had a conversation with someone who had just moved cross-country to a new apartment. "Got that Windmill hooked up to the window," she told me, as if she were name-dropping her cable company. "It's lit." I had seen the minimalist window air conditioning units in the background of some home decor Instagram posts, but didn't realize the company, which launched in 2020, had become another direct-to-consumer household name.