Usually this occurs on weekends after six pm and the companies they partner with are all charging emergency fees. i have had emergency services come for a thermostat that the vacationer couldn't figure out how to use. $200 for an hvac guy to say "turn the dial like this". 

It seems crazy to me to share the same refrigerator and thermostat.

It'd be even more of a pain when dealing with TVs and smart thermostats. 

.$74.00 Emerson Sensi WiFi smart thermostat - https://www.amazon.com/Emerson-Thermostat-Version-Energy-Cer...This is the exact one we have in our lake house.

The thermostat control is on the living room which will be part of the JADU.

"well, not like it used to" Ok, well what do you have your thermostat set on?

It appears guest somehow (by setting thermostat at below 61 degrees) about $450 of electricity.  

You can get:-$10,000 per unit for mini-splits - $5,000 per unit for knob and tube removal - 75-100% off insulation- FREE light bulbs and light fixture- FREE thermostats- FREE Shower HeadsWe just got $20,000 for knob and tube removal at a 4 unit and $30,000 to replace this shared boiler at a 3 family we own.

Maybe the thermostat is not working correctly.

If you do install any Cadet heaters though, for the love of god please pair them with the manual knob-style thermostats - the Cadet electronic programmable thermostats are maybe the single worst product I've purchased in my renovating life, and were replaced almost immediately after installing them.Doors and Trim.