At one time, the best models of furnaces featured single-stage operation. The heating system was strictly able to blast at maximum capacity. When indoor temperature fell below the thermostat setting, the furnace would start up and blow air at full capacity. Once the indoor temperature rose up to meet the thermostat setting, the furnace would shut down completely. This repetitive on and off cycling created unpleasant temperature swings. Eventually, the industry introduced two-stage operation. These improved furnaces are able to operate at high and low speed. Today, advances in engineering have led to adaptable-speed technology. Modern furnaces are able to reach AFUE ratings of 98% by automatically adjusting output to satisfy the exact and changing demands of the indoor space. The heating system can adjust in tiny one percent increments anywhere between forty and one hundred percent speed. There is rarely a time when the furnace is required to operate at maximum capacity. Most of the time, the heating system can run at lower speeds. This innovation has provided a more consistent temperature. The furnace costs less to operate, makes less noise and has less impact on the environment. Components tend to offer superior reliability and longevity. There are fewer concerns with insufficient humidity. Along with adaptable-speed technology, new furnaces include wifi connectivity and zone control. Each room can be set to a different temperature, accommodating personal preference for comfort, occupancy of the space and those areas that tend to be overheated or chilly. Plus, adjustments can be made through an app on a smartphone from virtually anywhere.