A barbecue grill is rated at 1,500 Btu per hour. How many foot-pounds of energy are released in one hour?

The problem is simply asking us to convert the units from BTU to units of foot pound force. To do this, we use the conversion ratio 1 BTU/778.169 ft-lbf. We do as follows:

1500 BTU/hr (777.169 lbf-ft / 1 BTU) = 1165753.5 lbf-ft/hr

Hope this answers the question.