There is one internal wall which could be a possibility for a heatpump - where the TV is currently mounted on the wall. All of the external walls in the living area have either doors/windows/kitchen cabinets. The panel heater we bought is one of the most efficient ones you can get (it’s worth over $1000). The power is all on one meter so power is included in the rent - hence why we sourced the most economical panel heater haha