I have a 10,000 gallon above ground pool and want to get a heater. The fuel company we use is certified in Hayward heaters. I found one online for a good price online. It is 100,000 BTU. Can anyone help me calculate what it may cost to run this thing for the summer? Would like to keep the pool at 80· It seems like right now the water is only dropping a couple degrees at night. even though the weather has been pretty could (in the 40s).