These units are the easiest and most affordable AC units to install while also taking up the smallest footprint of space. We install a steel framed cutout for these to fit through and then a base to hold the actual AC unit on the outside. There are heating and air combos as well as just air conditioning units available ranging from 12,000 - 18,000 BTU. You will want a BTU comparable to the size of the container you choose for max efficiency. It is important to remember that these units will need to be installed on the outside of the container for proper airflow and ventilation. They are able to be plugged into an installed outlet on the interior of the container.