Another way I have handled this in unheated basements is to install a small electric baseboard heater with a thermostat.

We have upgraded the baseboards to hydronic, and upgraded the old mercury thermostats to digital, and added insulation in all areas, which has helped to reduce winter time electric bills, but tenant turnover remains high due to lack of summertime cooling, and high wintertime electric bills (electric bills range from $50 to $400). 

They notified me that also the thermostat is broken and they aren't able to set it to a reasonable temperature, this is not good since as the landlord I need to keep the heat at a certain temperature (Right now in Maine temps are in single digits).

Hello,I would like to know if there are solutions to this problem:Despite the thermostat being set to 68-70 degrees, the tenants will plug in electric space heaters and drive up the electric costs.This is a 4 unit building and it would be very costly to add additional electric panels and meters.Thanks!

Not many work from home, so if internet happened to go out periodically.. it wouldn't be the end of the world; but I'd still like to have reliable connection - I have cameras and wifi thermostats. 

DO NOT use the cheap Nest Smart Thermostat.

When I bought Previous owner was paying for heat but had “Lockboxes” on thermostats in units to minimum 68 degrees.

It's all about having a rock solid team in place, systems, and processes to run things smoothly: Some of my favorite systems are: Hospitable - Channel Manager to automate messages, reviews, text to cleaners, syncs calendarsPricelabs - Dynamic pricing softwareHostfully - Online guidebookSchlage/Yale lock - Keyless entry lockMinut/NoiseAware - Noise sensorRing Doorbell - Security cameraNest Thermostat - Monitor temperatureFurnishing/supplies list calculator Property onboarding form 

I have several units in TX where I pay for heating/cooling and have installed a smart thermostat.

Owned water softener, owned alarm, and nest thermostat.