Did you ever buy & install a 500 gallon above ground propane tank?
Over 10 years, if it's filled four times a year, the captive cost is about: $60/month rental over 10 years = $7,200 4 fills/year at $3.50/gallon = $7,000 Total 10 year propane cost comes to about $14K (depends a lot on prices)
In contrast the customer owned tank (COT) costs would be lower in both ways: 4 fills/year at $3.25/gallon = $6,500 (assumes 25 cent/gallon COT discount) Assume one inspection per 10 years is about $500 (give or take) Total 10 year propane cost comes to about $7K
Did you ever have an above ground 500 gallon propane tank delivered (in this situation the hookup is easy as it's already on a cement platform)?
Which company did you use & how much was it for that 500 gallon install?