Originally Posted by Denis mcintosh
The label shows INPUT is 10,000 BTUH and OUTPUT 7,000 BTUH.
Input BTUH is the amount of energy contained in the fuel consumed per hour of operation.
Output BTUH is the amount of energy contained in the heat that goes into your camper per hour of operation.
The difference is due to the inefficiency in burning the fuel and heat that goes out the exhaust instead of into your camper.
When calculating how much fuel you are going to use in an hour (running the furnace full-blast) use input BTUs.
When calculating how hot it's going to get in your camper, use output BTUs.