When Do Programmable Thermostats Save Money and When Don't They?

Programmable Thermostat

It might surprise you to learn that simply installing a programmable thermostat won't automatically lead to energy savings or reduced bills.

In fact, it can lead to increased energy consumption if used incorrectly!

The Two Most Common Reasons Programmable Thermostats Don't Save Money

1. Failure to understand how to program them

The Problem:
Many people find their thermostat programming interface difficult to understand and instead of setting the desired temperatures they would like at various times of the day they often simply put them into 'Hold' mode most of the time - this overrides the program and essentially means they're using it like it was a manual thermostat.

This isn't just my opinion, there is quite a lot of research the topic. In fact Chris Mooney at the Washington Post pointed out that over 50% of people don't program their thermostats correctly - read his excellent report here.

The Solution:
If you're going to get a programmable thermostat then you need to spend the time necessary to read and understand the manual. If you're not prepared to learn how to program one then you can solve the problem by buying a learning thermostat which learns your patterns of heating and cooling over time and effectively programs itself - both Nest & Honeywell provide these options.

2. Not programming setbacks

The Problem:
Some people who do set up daily or weekly programs don't enter appropriate setbacks. These are when you program lower energy use such as lowering the temperature in winter for times when you're sleeping or going to work.

The Solution:
Simply program setbacks for the times when you typically don't need as much heating or cooling. If you have a change in schedule, there's no problem. simply use the 'hold' feature to keep your home warm if you're staying up late or not going to work - the program will then reset at the programmable period or when you take the hold off.

How Much do Setbacks Save When Done Correctly?

You can expect to save 1% for every 1°F the temperature is reduced by for an 8 hour period - source energy.gov.

Let's say you usually have the temperature set to 70°F in the evenings and you program a setback to 60°F for eight hours every night - this will produce a savings of up to 10% on your heating costs.

Or for the example above, let's say you sleep a little less or you prefer the heat to come back on before you wake up and you program the setback for 7 hours, then you'll be looking at savings of up to 8.75%.

I actually prefer it to be quite cool while I'm sleeping, so I go for a much lower setback all the way to 50°F - according to the example above that nets me up to a 20% reduction in heating costs by not keeping the house at 70°F all night.

How Else Can I Save?

It's quite simple really, the closer your home is to the outside temperature the more you'll save. This is because most of the energy you use is restore the heat that is slowly 'leaking' outside where it's cooler (assuming we're talking about winter). For a detailed explanation of this principal read If You Think Thermostat Setbacks Don't Save Energy, You're Wrong!.

There are two easy ways to take advantage of this fact:

  1. Maintain a lower temperature and wear warm clothing and slippers while inside - this is what my Nana used to make me do.
  2. Make sure you're not losing heat unnecessarily by stopping drafts, closing doors and windows, and only heating the parts of your home that you need to - IE don't leave the door to the basement open.

Summary

Learn to use your programmable thermostat correctly, program setbacks for when you don't need greater warmth, or get a smart thermostat which can do these things for you automatically, and you'll enjoy the savings modern thermostats offer.

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