Residential buildings with high performance thermal enclosures and thermal mass have been demonstrated to have daily temperature swingsof less than a few degrees. When such buildings are built on slab foundations with radiant floor distribution it is possible to utilize the mass todelay the delivery of cooling to times when lower outdoor temperatures result in higher energy efficiency ratios (EERs). This paper presents theresults of more than a year of monitored performance of a hot climate house and calibrated simulations that demonstrate the energy savingspotential as well as the capability to fully shift load to times when the cost of generating electricity is lowest, and identifies strategies foraccommodating latent loads.