A Propane to Natural Gas Conversion does not necessarily require all new equipment. Most Propane burning equipment is actually a Natural Gas appliance with a Propane burning nozzle installed. The Propane nozzle can be removed and the same appliance can then burn Natural Gas.
The potential caveat is that burning Propane is harder on a Furnace than burning Natural Gas. When the HVAC professional comes to make the nozzle change he may find that the Heat Shield is cracked on an older system. If the Heat Shield of a furnace is cracked you will likely need a new furnace, regardless of which fuel you are burning.
Once all of the home's Propane appliances are converted to Natural Gas, and the Propane tank is no longer being used it must be removed per New Castle County ordinance. The removal process for a propane tank will depend on if it is a company owned, or homeowner owned propane tank. Each residents should contact their own propane supplier to determine who owns the tank, and what the removal process will be.
Oil Tank Removal
It is possible that a house has a Propane furnace but still has an old Oil tank as well. There was a time when New Castle County Code allowed for unused storage tanks to be left abandoned in place while no longer in use. Under current New Castle County Code this is a violation, and the old Oil tank will need to be removed when the current furnace is replaced. For more information on removing an Oil tank see the Oil to Natural Gas Conversion page.