90,000 BTUs - the 090 is what tells you the BTUs of the unit.
80000
You take the size of your home in square feet and times it by how many rooms you have. A 70,000 BTU furnace will heat a house 1600 square feet.
30000 btus for every 400 square ft
30000 btus for every 400 square ft
4800 BTUs will 150 square feet.
The BTU input and output ratings are on the same tag as the model #.
how many square feet will 26,000.00 heat
A general rule of thumb in estimating the size of furnace needed to heat a home is to find the square footage of the home, and multiply that by 45 BTU (British Thermal Unit). For a 3200 square foot home a furnace somewhere in the range of 144,000 BTU would be a reasonable estimation of the furnace size needed to heat the home. To find the most efficient furnace for any given home, however, it would be best to contact an HVAC professional who can perform a load-calculation.
about 12,000
The answer depends on the city. Somewhere like Colombo (Sri Lanka) will probably require 0 btus.
to calulate your btu needs,you can use this link: http://hearth.com/calc/btucalc.html