Heat pump technology is improving the category in a big way by lowering operating costs to consumers without any compromise on performance or reliability. WHY IT EARNED THE SEALOur experts in the Good Housekeeping Institute Home Improvement & Outdoor Lab have been testing A. O. Smith’s Signature 900 series of hybrid heat pump water heaters for the last few years. The latest in the model line, the A. O. Smith Signature 900 Smart Hybrid Heat Pump Water Heater with Hot Water Plus, delivers the same exceptional performance we’ve come to expect with several enhancements that make the all-around experience even better for homeowners. With this A. O. Smith water heater, there’s no risk of the water running cold in the middle of your morning shower. One note on installation: because heat pump water heaters are still relatively new, it’s important to work with a qualified installer to make sure the siting and hookup are done properly.