Which voltage model should I choose? 115V or 230V?Updated a year ago

That will depend on the slot you have open. The 230V systems require a double pole breaker, therefore, it will require two slots in your panel. The 120 V system will require a single slot. Please note that the unit has to be wired to the breaker or circuit. Wiring directly to a wall outlet might cause an extreme fire hazard. Consult a local electrician for more assistance on what type of unit you can install.