I just got my propane bill and was surprised as to how much I used- 263 gallons for 3 months. I'm not home much and keep thermostat low. I have an underground tank and furnace 5 years old. Goodman GMNT-120-5.

The label on the furnace says energy efficient, but I don't see it especially after this bill.

Are Goodmans a reliable brand?

How can I determine BTU usage per gallon of propane- hours furnace is on = gallons used conversion?

First get your tank tested for any kind of leaks. This would also include any couplings and lines. Check to see if your thermostat is working correctly and accurately. If you smell any gas inside your home, immediately have this checked out. Also get your furnace recalibrated.

You didn't say where you lived and it has been pretty cold up north lately, so possibly you have just had more cold weather. Also wind chill needs to be factored in as well as this does make a big difference. Also, make sure you have properly insulated your home with window caulking, doors, etc. as this could make a difference also.

Also, you said you keep your temp low. Just how low do you consider low? I keep my home a balmy 61 degrees both day and night and don't bother changing the thermostat setting. That's what sweaters are for... to keep warm.

I wouldn't complain too much if I were you as some guy on here not too long ago got a $400 bill for one month's propane usage, so you're ahead of him!

$400... I received my bill last week for $702 for on month, Pacific NW, mild winter, 2400 sq ft home.
Propane used for heat and hopt water... tyou tell mde