90,000 BTUs - the 090 is what tells you the BTUs of the unit.
80000
Most likely 42,000 BTUs, 3-1/2 tons
4800 BTUs will 150 square feet.
1 gal of #2 fuel oil (or diesel for that matter) has an equivalent of 115,000 BTUS. I say equivalent because it has a little more than that raw (like 136k or so) but the furnace that burns it is only around 85% efficient, therefore you only get 115K BTUS.
trane air handler tonnage for model BWV760P100A1
A small room is about 5,000 BTUs. Most people don't have a room that would require more than 10,000 BTUs.
5,000
There are approximately 6,700-8,300 BTUs per pound of lignite coal. A ton of lignite coal contains 20-24 million BTUs.
6,520 Btus
1 kilowatt is equal to 3,412 BTUs (British Thermal Units).
A romm 20x9 is 180 square feet. You will need 5000 to 6000 BTUs for this.