Does anyone have the Pentair ETi high efficiency heater in their pool or the Pentair Hybrid Dual Fuel Ultratemp unit that uses natural gas and a heat pump? Want to save money heating the pool but don't want to wait super long time for pool to heat up. So many friends say they never use their heater except for the jacuzzi spa because it is expense to heat the pool. So instead of getting a Pentair Mastertemp 400 that these friends all have I am considering the ETi high efficiency or the hybrid dual fuel. Having a hard time deciding.