I Installed a Programmable Electronic Thermostat, Should You?

For the past several months I’ve been working to make my house greener by doing a number of DYI projects around the house. Thus far I have replaced our incandescent light bulbs with compact florescent bulbs, applied reflectorized metal film to sun-facing windows, installed dual flush toilets, installed low-flow shower heads and installed more efficient landscape irrigation. To be totally honest, I have done all this as much to save money as to save the environment. I hope that admission doesn’t make me a bad person in your eyes.

My family lives in a semi-arid region of Southern California where summer temperatures often reach and sometimes exceed 110 degrees. During those times it can be difficult and expensive to keep our home cool and landscape alive. When I say expensive, I mean electric bills exceeding $400 per month and water bills pushing $200. The months of August and September often see days where the air conditioning runs around the clock, especially when night time lows are still in the nineties.

When I recently had our central air conditioning serviced, the technician suggested installing a programmable electronic thermostat in place of the aging, mercury switch thermostat that came with the house. He told me of the numerous advantages of doing so but my ears really perked up when he mentioned that I could save up to 33% on my energy costs with a programmable electronic thermostat. That could be as much as $133 on a $400 monthly electric bill. I immediately decided I should follow his advice.

So I sat down in from of my computer and started to research home programmable electronic thermostats and found that two manufacturers dominate the home market, Honeywell and Rite-Temp. I also found you can spend anywhere for $25 to a couple hundred dollars. Thermostats are available with remote control (even over the internet), remote temperature sensors, touch screens and much, much more.

I was looking for a basic model that would allow me to automatically adjust the temperature based on a simple schedule yet still provide the energy savings I was looking for. I didn’t need all the bells and whistles found in the expensive models. Programmable electronic thermostats typically can be programmed 3 ways; 7 day programmable, 5-2 programmable and 5-1-1 programmable. A 7 day programmable can have each day programmed individually, a 5-2 unit allows you to program Monday through Friday differently from the weekend and the 5-1-1 units allow you to program the weekdays and Saturday and Sunday with different schedules.

I ended up settling on the Honeywell 5-2 Day Programmable Thermostat (Model # RTH2300B) for my home. It is a 5-2 day schedule model with a backlight. Since I didn’t need to be able to program Sunday any differently from Saturday, I had no need for a 5-1-1 day programmable unit. I chose the Honeywell unit because of their reputation in the market, reviews of the unit on the internet, the recommendation of my AC technician and because the existing thermostat was also a Honeywell. I hoped that by staying within the same brand it might make installing the new thermostat easier.

The Honeywell model I chose has the following features:

• One program for the weekdays; a separate program for the weekends, up to 4 periods per day
• Easy to use, basic operation keeps programming easy
• Backlit display, easy to read, even in dimly lit rooms and hallways
• Precise temperature control, this thermostat holds +/-1F accuracy to maximize comfort
• Energy savings, save up to 33% on your energy bill (if used as directed)
• Designed to install in 15 minutes or less
• Compatible with most heating and cooling systems (does not work with electric baseboard heat (120-240V), heat pump systems and multi-stage heating/cooling)

I purchased the Honeywell thermostat at a local Home Depot outlet for $24.98 plus tax, of course. They are also available at most other home improvement centers and available online at Amazon and other sites.

Easy Installation

The instructions say the unit is designed for easy, 15-minute installation. This is just about right, if you don’t include the time taken to sit down and read the installation instructions thoroughly which I highly recommend. The installation truly was easy and within the reach of just about anyone with some basic tools.

Required Tools

To install this and similar thermostats you will need the following:

• Small flathead screwdriver
• Small Philips head screwdriver
• Wire Strippers
  
• Utility knife
• Touch up paint
• Hole putty

Before You Start

Before you start to remove your old thermostat in preparation for installing your new thermostat be sure to turn off the power to your air conditioner and furnace at the service panel. This will insure you encounter no live circuits when installing your new thermostat.

Remove Your Old Thermostat.

You will want to be careful removing your old thermostat so that you don’t damage your wall. This is where the utility knife comes in handy. Your old thermostat may be stuck to the paint on the wall especially if it had been painted around. Use the utility knife to carefully score the paint along the edges of the thermostat. Don’t cut deep, just enough to separate the thermostat from the paint. This will keep the drywall paper from tearing when you remove the old thermostat.

Remove the cover of your old thermostat. Most snap on but you may need to remove a screw or two to remove the cover. You will see anywhere from 2 to 4 screws holding the guts of the thermostat to the mounting plate. Mine had 4 screws. Remove these screws and set aside.

You should now be able to remove the thermostat from the mounting plate. You will notice a number of wires coming through the wall and attached to the thermostat. Note also that the thermostat will have a letter associated with each of the wires, usually C, R, Y, W, B and X.

Before you disconnect these wires from the thermostat, use a piece of tape to mark each wire with the appropriate letter. Normally, the color of the wire will correspond with the letter on the thermostat. This may not always be the case, thus, the need to mark the wires.

Unscrew the terminal screws and disconnect the wires. Set the old thermostat aside. We will discuss what to do with it later.

The old mounting plate should be all that is attached to the wall at this point. Remove the mounting screws holding the mounting plate and set aside. Mine had 4 screws hold it on. Carefully remove the mounting plate being careful not to tear the drywall paper.

NOTE: There is a very good chance that your new thermostat is noticeably smaller than the old one. You may need to paint the installation area, if the old thermostat had been painted around. You may want to pick up some touch up paint when purchasing your new thermostat.

Installing the New Thermostat

Installing the new thermostat is essentially the reverse of the removal but with a few caveats. First, your new mounting plate may not require the same number of screws to hold it on. In my case, the new Honeywell mounting plate only required 2 mounting screws. If this is true for your installation, you will need to fill the extra screw holes with putty and let it dry prior to painting (if necessary) and installing the new thermostat.

I was also fortunate in that the 2 required holes for the new mounting plate aligned perfectly with 2 of the 4 holes from the original mounting plate. This was just what I was hoping for by purchasing the same brand thermostat. The original installation did not use wall anchors. The new thermostat came with them, so I carefully hammered the wall anchors into the existing mounting holes.

Next, pull the thermostat wires coming through the wall through the opening in the mounting plate. Then align the mounting plate over the mounting holes and attach the plate to the wall using the screws provided.

Once the mounting plate is attached, you can connect the wires using the chart in the installation instructions. Be careful to attach the correct wire to the correct lug.  If the wire colors do not correspond to the lugs, use the letter you taped to each wire.   Some new thermostats will not use all the wires required for the old thermostat. If that is the case (as was mine), be sure to cover the exposed end of the unused wire with electrical tape to prevent it from shorting against any other wires or metal parts. Push the unused wire(s) back through the mounting plate hole and into the wall.

Once all the wires have been connected to the correct lug on the thermostat mounting plate, it is time to mount the thermostat itself.  Position the thermostat body onto the top the mounting base, swing it down and snap it shut.  Some thermostats require a screw or two to tighten so read and follow the instructions for your particular model.  Most programmable electronic thermostats require a battery or two to maintain the programmable memory.  Install new batteries being careful to observe the correct polarity.

Once installed, restore the power to the AC and furnace at the service panel and test that your heater and air conditioner cycle on and off normally.  If everything works normally, your installation is complete!

Initial Programming

The Honeywell thermostat I purchased came pre-programmed with an energy saving schedule that can save up to 33% on your energy bills. I elected to use the default schedule until I get some idea how much it saves and where I will need to tweak the schedule.

So, the initial set up for me entailed setting the correct time on the unit, whether to use a 12-hour or 24-hour clock and that was it. As programming thermostats varies from unit to unit, read and follow the instructions in your manual to program your thermostat. You should give this some thought to ensure that your program fits your lifestyle and allows you to make best use of your new thermostat. If in doubt, most come programmed with a default schedule that will get you started.

Compressor Save Feature

Most new thermostats come with a compressor save feature. An AC compressor experiences the most stress when it first starts up. If a compressor starts up before the pressure from a previous cycle has had a chance to equalize, the compressor is subject to even more stress, wear and tear. If this happens frequently enough, it can significantly shorten the life of your AC compressor.

The compressor save feature prevents the compressor from restarting for a period of 5 minutes after it last cycled off. This gives time for the pressure difference between the high pressure side and the low pressure side of the system to equalize allowing the compressor to restart with the least stress possible.

My Honeywell thermostat came with this feature turned on by default. I left it that way and recommend you do likewise to help extend the life of your compressor.

Disposal of the Old Thermostat

If your old thermostat uses a mercury switch, then you can’t legally dispose of it by throwing it in your trash. Mercury is a highly toxic chemical that needs to be disposed of properly. If you have this type of thermostat, contact your waster disposal company for instructions on what to do. Additionally, some states like California have laws restricting the disposal of electronic waste. Anything with a circuit board or cord, including a thermostat, can only be disposed of at approved waste disposal centers.

Since my old thermostat still worked fine, I cleaned it up and offered it for free on Craigslist to anyone who needed it. Maybe you can help some family in need in a simple but practical way.

What are the Results?

We’ve had our thermostat installed for several months now and are very happy with it. Being digital certainly makes it easier to accurately set (time and temperature) and to use. Also, since the thermostat is programmable, we no longer accidentally forget to turn the AC off or come home to a stifling hot house because it hasn’t been on all day. We have it set to turn off when we head to work and to turn on about 15 minutes before we get home.

For those times we need to deviate from the program, the programmed temperature can be changed temporarily simply by pressing the up or down button to set the desired temperature. The new temperature will be in effect until the next program period is reached when it reverts back to the programmed temperature.

To determine if the thermostat is indeed providing the energy savings we hoped for we need to compare usage from year to year for any given month, i.e. compare July 2010 to July 2009. Our electric bill very conveniently provides our total kilowatt hour usage from the previous 2 years for comparison. While we haven’t seen a 33% savings as suggested in the manual, we have seen around a 25% drop in our electricity usage and a resultant drop in our bill. Keep in mind that this was using the default program that came with the new programmable electronic thermostat. I plan to experiment with the programming to see if we can realize even greater energy savings in the future. I don't know about you but saving $100 a month off my electric bill isn't chump change to me!

Bottom line, we love our new programmable electronic thermostat. We saved enough money on our first month’s electric bill to more than pay for the new thermostat and the savings continue. We no longer have to hover over our thermostat to ensure it doesn’t run all day and still remain comfortable. We also sleep easier (not literally) knowing that our AC compressor no longer cycles on and off constantly saving much wear and tear and prolonging the life of our unit.  It is clear to me installing a programmable electronic thermostat was a wise decision that not only will make us more comfortable but also result in substantial energy savings.

Now we look forward to the winter season to see how much it helps save on our natural gas bill. I installed a programmable electronic thermostat, should you?