MRCOOL DIY 4th Gen 18,000 BTU Mini Split vs MRCOOL DIY 5th Gen E-Star Series 18K BTU, 1.5 Ton, 21.5 SEER2 Ductless Mini-Split Heat Pump System with Ceiling Cassette Air Handler – R-454B

Both are 18,000 BTU MRCOOL DIY single-zone heat pumps, so capacity and the DIY pre-charged line set are shared. The 4th Gen is the simpler, proven wall-mount system with broad smart-home support and a conventional indoor head. The 5th Gen E-Star steps up on efficiency (21.5 SEER2), uses R-454B refrigerant with lower global warming potential, and puts the air handler in a ceiling cassette that fits between 16-inch joists for a low-profile look. Buy the 4th Gen for a straightforward wall install and easy app control; buy the 5th Gen if you want the higher efficiency, newer refrigerant and a ceiling-mounted head.

• Choose the MRCOOL DIY 4th Gen 18K if you want a familiar wall-mounted head, Google Assistant and Alexa control, and the simplest DIY install.
• Choose the MRCOOL DIY 5th Gen E-Star 18K if you want higher efficiency, the newer R-454B refrigerant, and a discreet ceiling cassette that fits standard joists.