"Ty Colman, a cofounder and the chief revenue officer at Optera, a carbon-accounting firm that helps organizations quantify their emissions, said that in general, a fully remote company with no offices has the lowest impact-per-employee per year, at less than 1 metric ton of carbon-dioxide equivalent. That includes the uptick in energy used to power computers, keep the lights on, and maintain a comfortable temperature at home."
(versus 1.4 tons for hybrid and 1.7 tons for full time in the office). There's quite a lot more about the effects on the environment in the article.