The unit is now trashed (expected) but things are missing (e.g. bathroom mirror, thermostat). 

I do have regulated locked thermostats so I know there is no- over use  

I'd give more consideration to the end user interface... the devices, how well the rooms heat up, air flow, and thermostat controls.

He may think the heat is on because he adjusted the thermostat before he left.Give him notice that the heater is not kicking on and you intend to enter the unit to inspect and verify the heat is operating.

We've now started investing in a few high tech features such as programmable thermostats and smart locks to keep up with the demands of our target audience.

Think clunky looking light switch & electric outlet covers, thermostats, door knobs with "brass" plating peeling off, etc.

On the money saving note I wish I could post photos so you could see my 12$ smart watch, my air mattress ,and my scotch taped at 68° thermostats.

I didn’t find any unicorns yet of how to keep it super warm but will see if the cover makes a material difference Insulate your pool: Adding a pool cover or blanket can help to keep heat in the water and reduce the amount of energy needed to maintain a comfortable temperature.Set the thermostat correctly: Set the thermostat to the desired temperature and avoid making frequent adjustments, as this can cause the heater to cycle on and off more frequently, which can increase energy usage.Keep the heater clean: Make sure to clean the filter and other parts of the heater regularly to ensure it is operating at its best.Use a timer: Use a timer to turn the heater off when it is not in use.

You cannot set limits on thermostats, water usage, etc., nor can you charge a differential above a set amount.  

Plus we have an Emerson Sensi WiFi thermostat.