We are talking LPG but his LPG gas bill is high and he’s considering switching to LNG or compressed natural gas(CNG). I assume there are no natural gas utility lines close enough to connect.
LNG needs to be stored around -270 F and requires special handling so I doubt he could have it delivered in that form to his store. I’m not sure about compressed natural gas but it would be a massive tank based upon his daily BTU needs. By the way, propane is made from natural gas. Since propane is a 3 carbon molecule versus a 1 carbon molecule(NG), it can be stored in the liquid state at room temp under around 100PSI of pressure.
When I looked at fuel cost of the two fuels a few years ago, it was approximately 1/2 the cost to run a kitchen with grid supplied natural gas versus propane in my area.
Based upon a $2,000/month bill it sounds like rg is using around 1500 gallons per month or 50 gallons of propane per day. That seems high.
What kind of ovens and other equipment are you using rg? If you have a double conveyor oven, do you turn the extra ovens on only during the push? Are the air loss prevention shields at the end of the entrance and exit of the conveyors as tight as they can be given the product your cooking.