There are basically four types of furnaces, Single Stage, Two Stage, Two Stage Variable Speed and Modulating Furnaces. A single stage is a simple furnace that has only one speed and one heat setting. Once the unit starts functioning it will not shut off automatically even when the temperature has reached the thermostat setting. It is a cheaper option in furnace and comes with 5 year warranty. It makes loud noises while functioning. For a 60000 BTU furnace it may cost around $2100. The cost of running the unit is higher compared to the other ones.
A Two Stage furnace works in two stages. As soon as you switch on the unit first it will work at a lower stage and then it increases the burner to its maximum for attaining the set temperature on the thermostat. A 60000BTU Two Stage furnace will cost around $2300. A 2 stage Variable Speed furnace have more speed options on the blower motor. The furnace ensures more comfort. The air flow is more with this type of furnace hence all the areas will be heated. Whenever the temperature drops the furnace blower will increase its speed to make up for the drop in temperature. The price of a Two Stage Furnace is around $2800 and it has a lesser operating cost compared to the above two types of furnaces. Modulating furnace functions similar to a variable speed furnace, the only difference is found in the functioning of the blower motor as it ramps up and down. It generally has a DC motor. It is the most expensive type of furnace and will cost around $3200 for a 60000 BTU furnace.