It is not cheaper to heat with propane at current prices...you get a lot more BTUs out of kerosene.
In Watauga county, 250 gallons of propane costs $2.80 per gallon and 250 gallons of kerosene costs $3.77 per gallon.
One gallon of propane yields 91,000 BTUs.
One gallon of kerosene yields 135,000 BTUs.
7.4 gallons of kerosene=1 mill BTUs, cost $27.93
10.99 gallons of propane=1 mill BTUs, cost $30.77
This really adds up over time. It is not cheaper to heat with propane at current prices and that is why Monitor and Laser heaters that operate on K1 Kerosene are so popular in the High Country where the temperatures are sometimes extreme.