I have no idea what gas costs in your area but run the numbers and make certain it isn't cheaper to run on gas. Natural gas in many places tends to be cheaper than electric for heating. Yes the up front costs might be more but that's a one time cost.My guess is gas is at a minimum double the cost.
And the initial cost is thousands of dollars plus heater. Between permit, running the gas line out, etc. etc. I can save some of the cost digging the whole myself but still it will be very costly.
I have an electrical outlet. Now I just realized that it probably has to be 20A? (it might be that anyway)
EDIT: Nevermind, my pump and lights are on 20A circuits.
Heat pumps are an AC unit so you should install a dedicated line for the heat pump. Include a quick disconnect to it. You need to look at the requirement specs per the manufacturer. Probably need at the very least a 40-50 amp dedicated circuit.