You shouldn’t close more than one register in your home. Closing off or even adding coverings registers will not save you energy because they still will have heat gain from the outside. This heat gain is transferred to the rest of the house through doors, walls, and ceilings causing your AC to work just as hard as if all the registers were open.
What is the difference between Gas Heat and Heat Pump?
A gas heat furnace typically uses natural gas or propane to create a flame that heats metal heat exchanger plates, inside the furnace. Air from the home is then blown over these hot heat exchangers and is then returned as warm air to the house through ducts.
A heat pump does not use gas and is simply an air conditioner running in reverse. To supply warm air, the unit reverses the normal refrigeration cycle and transfers heat from the outdoor air to the inside of the house through the refrigeration inside the system.