Looks like the mini split inverter technology is now available in a window unit. LG is offering the first window inverter for sale in the U.S. Not a bad price at $469 either. The EER is significantly higher than a traditional window unit. They are claiming a 25-40 percent energy reduction compared to a standard window unit.
https://www.digitaltrends.com/home/lg-smart-ac/
(broken link removed to https://www.lg.com/us/air-conditioners/lg-LW1517IVSM)
https://www.digitaltrends.com/home/lg-smart-ac/
(broken link removed to https://www.lg.com/us/air-conditioners/lg-LW1517IVSM)