The info you provided isn't enough to size the propane tank. You also need to consider the scenario and what applainces will be running at the same time and for how long. The big drivers will be the heating system, freplace, generator and hot water. Find out the gallons per hour ratings for each of these and multiply by the number of days you need. Keep in mind that the propane tank is only filled to 80% of maximum capacity to allow for expansion, so a 500 gallong tank will only have 400 maximum gallons; 1000 gallon tank has 800 gallons. Also- you need to figure that when an outage occurs you probably won't have a full tank. I looked at the Kohler 15kW specs and it is rated for about 1.5 gallons per hour of propane usage at a 50% load (idle speed). A 2 week outage would use over 500 gallons assuming you ran the generator continuosly for that entire time. So that alone would put you in the 1000 gallon tank class. But I would really think hard about this 2 week requirement. If that is what you really want - then you probably would need a generator that is liquid cooled and not air cooled (air cooled are cheaper). The liquid cooled gensets may consume more fuel - check the specs. 2 weeks of continuous operation is a long time on a genset. I worked out the tank capacity with the propane service provider. They not only sized the tank, but they also provided a special valve to ensure that the pressure was regulated when the genset is running. The tank size won't change the gas pressure coming into the house since it the regulator keeps the right pressure. I would also look at the genset size. Since your hvac is gas, you don't need a lot of power to keep the house comfortable and rive all of you appliances and well pump. A smaller generator will use less fuel and will be cheaper to install. I have a 12kW Kohler unit and it is more than enough to run the house during an outage. We live in VA and have had some long outages - over 24 hours with no power with near zero degree temps is a long outage. The 12kW works like a champ. Also - make sure you get BOTH the carburetor AND batttery warmer heater accessories for your genset. These are a must in cold weather and will make sure the unit starts in very cold weather.

A local Richmond, Va TV station recently did an expose on this industry. As it seems in the South Propane Dealers are NOT REGULATED in terms of home much they charge, what delivery fees are or what proper business practices & policies should be. This is why they get away with locking you in. Charging you more if you are not "their" customer and putting you on a minimum purchase required plan. It is all done in the name of their profits not yours. Personally after I found out I could buy my own 500 gal tank for 1500 & get my excavator to bury it. Pay a plumber who was a gasfitter to run the line to my house & fireplace & generator . I decided it was cheaper to do it myself & contract the jobs. Their charge would have been 5500. Then I would also be locked in to purchase my fuel only from them. Thats a bunch of crapola. Saved 3 Grand doing it my way. My excavator charged me only $200 to bury it & the plumber charged 800 for the line & the fittings. Their is very little required maintenace for this tanks. Don't let them pull that ruse on you!!!!. Here is a link that might be useful: WWBT12-Propane annual fee

Hm well I am far from an expert on this, but there is of course, (unfortunately for the environment, as unburned hydrocarbons are a serious source of pollution) a certain amount of wastage as (at least in my bbq-bottle filling experience) they fill the tanks, to allow bleed off etc) but I agree, this probably has nothing to do with technical issues, and all to do with profit. Perhaps you should talk to your rep again, and discuss contacting the bureau of weights and measures (or relevant authority in your area) because their equipment doesn't measure correctly, or it's a form of 'price gouging' - not unlike where i work, where we tech support reps are now forced to try to sell to our customers as well, and are supposed to add a $1.99 'handling fee' every time we sell to our (U.S.) customers. Most of us think it's loathesome and counter to good sales, so 'forget' to add the fee.

Underground tanks will be and must be listed as underground tanks, this info is on the data plate. There are three types: aboveground(AG), AG/UG, and underground(UG). The AG/UG tanks can be used in either service. The underground tanks usually have some form of an epoxy type coating instead of paint, and scratches in the coating should on be repaired with the same coating available from the manufacturer. Anodes are used to protect the tank from corrosion, with magnesium being the most common type but depending on soil conditions other types are used as well, and a certain size anode or multiple anodes are used depending on soil type and tank size. Clearances from property lines, structures, wells, buried power lines etc. must be met as well. Most LP companies do this quite often and can line up everything needed to do it. It is recommended by the anode manufactures that the space around the tank be backfilled with the original soil, or completely with sand but never both unless thoroughly mixed. Rocks should be removed from the backfill and special care should be taken to prevent damage to the coating while backfilling. It is a very simple job to do, usually taking about 30min to one hour to do.