Traditionally gas furnaces have been single stage: they are either off, or on, operating at 100% of their capacity regardless of the actual heat load required. Single stage furnaces cycle more, and tend to result in wider indoor air temperature swings and larger differences in indoor temperatures from room to room. Two stage, or multi-stage gas furnaces operate at a lower output capacity most of the year based on either a multistage thermostat, an outdoor thermostat, or the onboard logic of the furnace control. When the furnace operates and a lower output level, the blower speed and heat output is lower, and the furnace will have longer, gentler furnace cycles. This improves indoor comfort and noise levels significantly. Modulating gas furnaces can operate across a broad range of capacities based on the immediate needs of the building envelop. As the heat required changes, so do the furnace capacity. The result is significantly more comfortable and quieter operation, and often lower operating costs. Variable speed gas furnaces also make air conditioning better by allowing for the possibility of staged or modulating cooling, and much better dehumidification.