If your furnace is beyond the repair limit and has become old and worn-out then you would start to realise that it need to be replaced. Once you make the decision of replacing your central heating system with a new one a lot of questions pop up in your mind. Relying blindly on a sales man will lead you to choosing a unit that they would get commission for, so it is necessary to do an extensive research on the various brands and models available in the market so as to save yourself from a biased choice. As a consumer you need to be aware of the different types of furnaces that are available in the market they are as follows, Single Stage, Two Stage, Two Stage Variable and Modulating. Before purchasing a unit you need to understand the significance of sizing the furnace.
The BTU rating of the furnace determines its capacity. Your furnace should not be over or under sized as it would significantly affect the efficiency of the unit. To calculate the right size you need to find out the total square feet of the space to be heated and then divide it by .04. For instance if the square feet calculated is around 1000 then dividing it by .04 you get 25000 hence you need to choose a furnace with 25000 BTU capacity. For older homes a more capacity unit has to be chosen as such homes lacks proper insulation. Keep in mind not to choose an oversized unit as it will consume more energy.