We are considering getting a York heat pump to reduce our heating costs.Need to know if anyone has done this.?

We are currently on propane and pay around $5000 per year for fuel. If I switch to the heat pump I am concerned about how much higher my hydro bill will be. If hydro goes up by 100% it will take about 5 years for the unit to pay itself off. Anyone know how much extra hydro it will take? My back up furnace will be electric- high efficiency instead of propane.The salesman could not give us much of a range as to the increased hydro and we are waiting to see if any of his customers can tell us their experience but we could use help from anyone out there...Thanks