Single-package rooftop units are most commonly used on 1 and 2 story buildings for heating and cooling service.
These are usually electric cooling with either electric resistance, gas or oil heating, or heat pump heating designs. A careful review of installed costs and operating costs should be performed before deciding on the type to be used.
Air-cooled condensers are typically used, unless ground water is readily available. However, most cities regulate against use of once-through city water for condenser cooling and mandate water conservation such as a cooling tower system. While water-cooled cooling units typically operate more economically than air-cooled, the added maintenance costs of the tower system somewhat limits their use to larger stores or central systems in shopping malls.