What Makes a Thermostat Smart?

Figure 22 – Making a device smart 

What makes a device smart? A thermostat is a great example. You can have dumb thermostats that that don’t do anything as well as thermostats on the wall that dial the temperature up and down. These dumb cheap thermostats don’t do much but are great for manual fiddling.

The user interface to a smart thermostat is provided by software, not hardware. This is an open-source thermostat interface which is similar to a nest, except that I still have a clunky programmable thermostat on the wall. But because it is a Z-wave thermostat I can find software for it that gives me the interface of a Nest thermostat, without the additional hardware cost. I can check on the thermostat through any device, cell phone or desktop, provided that smart hub is connected to a network. I can program with the thermostat. All of this advanced functionality does not come with the thermostat out of the box, it’s an  added value that comes with connection to a smart hub. 

Before getting started on a thermostat swap, be sure to power down not just the thermostat and outdoor unit, but the indoor unit as well. Failure to power down the system can blow a fuse in the indoor unit which will need replacement for the air conditioner to work. The fuse can be purchased at a local hardware store, but it is easily avoided by not rushing into the project.

Figure 23 – Thermostat Types 

Programmable thermostats are hated by many. They’re clunky and difficult to program but with the right peak versus off-peak rate structure, programming the thermostat correctly can result in real savings on the electric bill. But not all thermostat adjustments are easy. A proprietary “smart” thermostat may not have all the functions needed for easy programming.The Nest may be programmable for different zones at different times of day, but a regular programmable thermostat can do that too. But is a Nest solar friendly? Does it increase the air conditioner when the electricity is otherwise being sold for cheap back to the grid? Can its programming account for holidays or just days of the week?

Figure 24 – Smart Thermostat Functions 

A true smart device to me is one that can communicate with the other smart devices on your smart network, making it easy for this communication to result in computer-driven automations to do useful things. That doesn’t have to be a Nest. It can be a $40 clunky programmable thermostat so long as it has a Z-wave antennae.

After pairing a smart thermostat into the smart hub and enabling voice services, basic voice commands should work immediately. The smart hub provider often provides an automation menu for basic automation programming. But advanced programming features may require access to the software source code, so that you can program an energy automation such as to run the air conditioner harder when the solar array is being over-productive.