When I spoke to the guy at our local pool store who LOVES heatpumps (PA state), he told me the heat pump was the way to go if I did not have a spa ( I don't). He told me if you have a spa he prefers a split system with a gas heater to heat the spa. I don't know how you would plumb such a system. Do you plan to swim all year? and what are your winter temps? My pool is 17,000 gallons and I have a heatpump that cranks out slightly less than 100,000 BTU which is fine for just the pool.