The BTU of a home furnace should typically average between 40 to 45 BTU pre square foot, though this average applies only to homes located in cooler climates. Square footage measurement is generally considered a rudimentary calculation and can yield a large range of results.
When choosing a home furnace, it is important to get the correct size to maximize its effectiveness. An oversized furnace generally will often turn itself off and result in a larger electricity drain when it has to be turned on again. An undersized furnace can fail to sufficiently heat up a house while at the same time constantly draining electricity.