Yes, it’s fine to put the heat pump water heater in a finished basement. You should just make sure the cool exhaust air from the water heater does not blow directly into commonly occupied areas. Yes, this will add a small amount of energy to the home’s overall heating load. However, this amount of cool air from the heat pump water heater will have a minimal effect on the home’s overall heating system performance/consumption. In addition, the cool air will help keep the basement cool in the summer months, reducing the energy used for air conditioning.