Building operation accounts for a significant portion of global greenhouse gas emissions. Hawaii is committed to 100 percent clean energy by 2045. This study demonstrates a replicable process using early design phase energy modeling to reduce energy use in multifamily residential buildings in subtropical climates. The team simulated the design of air‐conditioned buildings that can reduce annual energy use 29–61 percent compared to the International Energy Conservation Code, with an additional 10 percent savings if air conditioning is not used. The results inform the design of multifamily residential buildings by identifying building characteristics with the largest impact on energy use, energy cost, peak loads, and greenhouse gas emissions. The study demonstrates that generating 100 percent of annual site energy is possible using a combination of design measures and rooftop solar panels.
