All About Electronic Programmable Thermostats

When used in heating and air conditioning systems, a thermostat contains equipment and controls to sense the temperature of a room or area and turn the air conditioning, heating, and fan on and off to maintain the levels set by the user.

Whether added to your existing air conditioning and heating or part of a new system, programmable thermostats are clearly one of the lowest cost, highest impact improvements you can make. Your decision will affect both your indoor comfort and the monthly utility bills for your home or business. Within the HVAC industry, thermostats are also known by the more general term controls.

Primary benefits of programmable thermostats

Increased comfort:

  • Maintain an indoor temperature range to match your comfort needs.
  • Have your home or office comfortable when you walk in without wasting energy the rest of the day or night.
  • If you prefer to be cool or toasty while falling asleep or waking up, you can set the temperature in your bedroom to change in the hours after you fall asleep, before you wake up, or both.


  • Save footsteps and time with fewer trips to your thermostat controls.
  • Make changes to the settings as often or infrequently as you want.
  • Have the option to make them remotely-either from another room in your house or with some models, from another location by telephone or internet.

Saves energy:

  • Lets you find and manage the balance between comfort and use of energy—either when you are present or away.
  • You can manage not only the overall temperature of your indoor space based on time, but the temperature sensitivity.
  • This determines how many degrees/ how often your HVAC system adjusts to changes in inside temperature.

A brief history of thermostats
Thermostat controls for indoor climates have benefited in a major way from advances in electronics. Before today’s electronic programmable models, the earlier thermostats contained mechanical components such as spring-like coil or a clear glass vial filled with mercury. As the spring expanded or contracted or the loaded bulb tilted one way or the other based on indoor temperature, it would make or break contact with an electrical circuit that would control the heating, cooling, and fan. This arrangement usually required the location of the temperature sensor and thermostat control to be within the same unit.

In addition to no moving parts or (toxic) mercury filled bulbs, some of the new digital thermostats offer, separate sensors, touch screens and other convenient features.

Features and costs of programmable thermostats
Thermostats must be compatible with the type of air conditioning and heating system they control and the power source for the thermostat. To deliver the best results, we recommend you get your thermostat professionally installed. Since labor costs vary around the U.S. and could be combined with scheduled maintenance on your system, we will not attempt to give installed prices here. Generally, the cost of the thermostat parts (not installed) will start at about $30 and go up to well over $100 depending on how many features you need. If you have a zoned system, plan on a separate thermostat for each zone.

Remote Access
Rather than the sensor being part of the control unit of the thermostat, on programmable thermostats the two can be separate. While the temperature sensor for each room or zone must be located within the room or zone the thermostat covers, the thermostat controls can be located most anywhere you like. If you have several zones you have the sensors placed where essential but the controls all in one place, such as a utility or security room. This is particularly useful where you:

  • Have one person responsible for energy usage for the home or business.
  • Wish to keep control of the settings from occupants, guests or children (without the use of a security device or cover over the controls or a security setting).
  • Want to change the settings without disturbing an occupant, guest or sleeping child.

Reset after power goes out
Since they are electronic and have a timer, programmable thermostats share some features with an electric clock. After a power sag or outage, the clock will reset on some thermostats. When this happens, you have to reset the thermostat time. If you don’t, any timed programs will run at wrong time or perhaps not at all, depending on the model. Look for thermostats that have battery backup power to help avoid resets.

If you are sometimes intimated by having to program electronics, don’t worry. Most programmable thermostats have logical settings. Some will divide your programming options into basic settings and advanced options. Most air conditioning and heating contractors offer several thermostat brands and models that are compatible with your system.

Advanced settings
One useful but less obvious feature to know about is the feature to adjust the number of degrees of drop (or rise) before the heating or cooling system will turn on to reach the target setting. When set at the optimum level, this saves energy, extra wear on the system, and avoids the extra sound produced during start-ups.

If you would like the option to change your thermostat setting while away from home, you should check out communicating programmable thermostats. These offer the option to connect your thermostat with your telephone or internet. For those who travel a lot or have pets at home, this could give extra peace of mind while you are away. In case you forgot to set your program before you left, it could also provide you with a more comfortable welcome home.

When it’s neither hot nor cold outside…
For those moderate times of the year or climates where the outside temperature pivots below and above your target indoor setting, it can sometimes be difficult to choose between heat and cool. On many programmable thermostats, you have to choose a mode—either heating, cooling, fan (or Off…) —along with a target temperature setting. To stay comfortable you might have to switch modes during the day.

There are a couple of possible solutions: (1) There are some thermostats that will make the mode switch for you, or (2) Heat pumps and their thermostats are designed to respond to this type of scenario. If you go with option 1, you will want to verify that the sensitivity settings on the thermostat are set at the optimum to save energy within your comfort level. This setting might be located in the advanced settings options.

Another factor to consider during the “shoulder” season or moderate latitudes is air movement without heating or cooling. To keep the indoor air moving, you can use the “fan only” setting. Some air handling systems give the option to bring in fresh air ventilation with the “fan only” setting. In case your current air conditioning and heating system does not offer this feature, you can ask about it when you go to replace it. Humidity control should also be part of this discussion. A related feature to consider is a variable speed fan. Keeping indoor air moving and fresh is particularly useful for rooms that tend to become stuffy overnight or in a multi-person dormitory type room.

Thermostats and energy conservation
Programmable thermostats play a major role in energy conservation for air conditioning and heating. They allow you to turn heating or cooling system down or off when not needed, yet have your home or office in a comfortable temperature range when you arrive. More thermostats now offer the advanced sensitivity settings. This gives you the choice to save additional energy by having a slightly wider range of temperature variance before the heating or cooling turns on to adjust to the target temperature. You can also fine-tune your thermostat to change to use less energy after you go to sleep. You can experiment with different temperature settings while you sleep to find the optimum temperature for your body.

Upgrading to a programmable thermostat is a low cost way to save energy on an older system in case you are not ready to invest in an entire new system.

Best way to get a programmable thermostat
To make sure the thermostat works correctly and for safety reasons, unless you are licensed for air conditioning and heating, have the installation done by your local HVAC contractor. To add one to your existing system, get the new thermostat installed during a spring tune up on the A/C side of your system or the fall heating inspection and tune up. When you buy a new air conditioning and heating system, you will be able to choose the power source, features, and brand of thermostat that matches your new system. When you make the appointment for the work, be sure to tell your contractor you want a programmable thermostat installed, in case this affects their choice of technician to send. The city links on the right side of this page include contractor information for your area.