Stop heaters right by the shop open door, it is all wasted energy. Shut the door. Have a "We are open / you are welcome" sign on the door.
Why is this important?
Climate change is the number one 'Hot Topic', excuse the pun. Shops try to make customers feel comfortable by having hot air blasting down on their head as they walk through the doorway. It is all wasted. Not rocket science, if I want to go in the shop, I will go in. Put a welcome sign in, save money AND the Planet's precious resources.