Stay cool while saving money and energy

If you could make the rest of your summer better, just by spending 5 minutes to program your thermostat, would you do it?

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Program your thermostat for the following:

  • 12am: 73 F; 23 C
  • 7am: 78 F; 25.5C
  • 5pm: 79 F; 26 C
  • 7pm: 77 F; 25 C

Then gradually change the schedule over the next few days - until you are comfortable.

Who should read this?

  • If you set your thermostat at one temperature all summer, you might be spending more on electricity than you need to.
  • If you like to put the AC on “max” whenever you want it “on” then swing it the other way to turn it off, it’s possible you’re not even as comfortable as you could be, all while wasting money.
  • If you want to reduce your energy consumption because you’re concerned about climate change, this might give you some ideas.

Programmable Thermostats

For this howto guide, you will need a programmable thermostat. The following links can help you to get started. This guide was written for Ontario (Canada) but the general idea will work in many countries.

How to buy a programmable thermostat

The most affordable thermostat that is programmable will cost about 40 CAD. In most cases, that’s all that is required.

How to install a thermostat

Installing a thermostat is a relatively simple home DIY project. Often times, the only tool required is a screwdriver.

  • https://www.youtube.com/watch?v=La9IyRWrRVk
  • https://www.youtube.com/watch?v=JGAvTG55iQs
  • https://www.youtube.com/watch?v=La9IyRWrRVk

How to program a thermostat

Cheaper thermostats tend to have fewer features - and they can actually be simpler to program, as a result. It may be as simple as pressing “set”, “up”, and “down” to program the disired times and temperatures.

  • https://www.youtube.com/watch?v=uun8HJhM3h4
  • https://www.youtube.com/watch?v=izEcRomoetY
  • https://www.youtube.com/results?search_query=how+to+program+a+thermostat

Facts about thermostats, temperature, and feeling cool

Consider how the following facts could make you happier and more comfortable:

Fact 1. Ontario - and other regions - charge different rates for electricity depending on when it is used. This means that the same task can cost more or less if you do it at a certain time of the day. Here is the Ontario electricity price/time schedule: https://www.oeb.ca/sites/default/files/rpp-graphics-tou-en.png

Fact 2. You feel cool when water evaporates off your skin. This means that what actually makes you feel good isn’t a specific number on the thermostat; it’s whether your body can cool off or not.

Fact 3. Moving air increases evaporation. Fans feel good because they move air across your skin. When your air condition is actively blowing cool air, it feels even cooler because it’s moving.

Fact 4. Humidity decreases evaporation; when there is already water in the air, it makes it harder for water to evaporate into it. This means that it is harder to sweat when the air is humid, so you feel hotter than the temperature would feel if it were less humid.

Fact 5. Air conditioners reduce humidity, which makes your skin feel cooler than the temperature otherwise would. When humid air is cooled, water condenses onto cooler surfaces, creating a puddle in/around your air conditioner’s condenser unit; this is good.

Fact 6. Your thermostat turns the AC on when the temperature is higher than the number you set it to. When the AC turns on, it gradually lowers the ambient temperature until the thermostat reads a value that is lower than the set value, at which point the thermostat turns off the AC. This happens automatically.

Fact 7. When the outside temperature is hotter than the temperature inside the house, then the house will eventually become the same temperature as outside - or even hotter.

Fact 8. The greater the temperature difference between indoors and outdoors, the more energy that must be expended to cool the indoors. When they are the same temperature, it requires no energy to maintain the indoor temperature. As the outside temperature increases, it starts to require electricity for Air Conditioning to maintain a specific indoor temperature.

Fact 9. The more extreme the thermostat temperature setting, the more difficult it becomes to maintain that setting. This means some temperature settings are actually impossible to reach. When the AC runs 24/7, that’s the maximum cooling it can provide. If the thermostat is set to a value even lower than whatever the AC can achieve, then that temperature is impossible.

Fact 10. Any time the ambient temperature is lowered, it feels cool to our skin. This means that if it’s 27C outside, then 26C indoors will actually feel cool. As long as the indoor temperature is ANY lower temperature than outdoors, it will feel cool to walk indoors.

Fact 11. Any time the AC turns on, it will feel cool. The simple act of the AC turning on is going to immediately change the sensation of the indoor air. This means that changing the thermostat temperature to a colder value will be immediately perceived and felt as a cool breeze.

Fact 12. The outdoor temperature changes throughout the day due to heat from the sun. Since the sun follows a pattern, the temperature also follows a pattern - and we can take advantage of this to predict what will happen on a regular schedule.

Fact 13. In order to guarantee the indoor temperature is lower than the outdoor temperature, the thermostat must be changed periodically throughout the day. Since the outdoor temperature constantly changes, then if the indoor thermostat is never changed, it might end up “out of sync” with whatever the weather is actually like.

Fact 14. A basic programmable thermostat can set the temperature to different values at different times of day. This makes it possible to use a time-based schedule to control what happens to the temperature in your house throughout the day.

Fact 15. There is an optimal thermostat schedule for YOUR house, region, time of year, etc, which is better than any other possible schedule. It’s easy to imagine how the thermostat can be “badly” programmed. So, the opposite is also true: it could be programmed “well.”

Applying the Facts

The optimal thermostat schedule takes into account the following:

  • the outdoor temperature throughout the day/night
  • the cost of electricity, based on the time
  • feeling comfortable, cool; better than it feels outdoors
  • your life’s schedule: wake, sleep, home, away

Every situation is different and these will all vary on an individual basis. Given those considerations, use the following schedule as a starting template for finding your own optimal schedule:

12am: 73 F; 23 C

We start the day by targeting a comfortable temperature. Since it’s midnight, the electricity prices are at their lowest - and it’s affordable to cool the home to this temperature. Also, since night is when outdoor temperatures are lowest, the least energy is required to reach the target indoor temperature because the temperature difference is at its lowest, compared to the outside.

This is a good time of day to drop the temperature in the home substantially because we are usually sleeping. Whenever the temperature falls so much, we perceive the dramatic drop as being cold - not just cool - and it can actually be uncomfortable to sit with the AC blowing on you for hours at a time. However, when this happens overnight, the temperature drop can actually feel really nice.

7am: 78 F; 25.5C

At 7am, Ontario switches to mid-peak rates, which are more expensive than overnight off-peak rates. During this time, many people are away for work until 5pm - so it just wastes energy and money to cool the home when nobody is in it.

At 7am, we set the temperature to a value that will be higher than the outdoors temperature for most of the day. Because the house was cooled overnight to 73F/23C, and because the outdoor temperature is also cool at the start of the day, it takes several hours before the indoor temperature starts to rise. This means the home remains a comfortable temperature for many mid-peak/on-peak hours without the AC running at all.

It might not be until the late afternoon for the thermostat to reach the set temperature, at which point the AC turns on. Even though 78F/22.5C would otherwise feel uncomfortable, when the AC starts blowing cold air throughout the home, it feels much cooler than 78F/22.5C. Therefore, the actual feeling/experience of 78F ambient temperature, along with cold AC blowing, is comfortable. You’d probably tolerate these conditions at the beach - and for many, 78F/22.5C with a cold breeze is a beautiful summer day.

Since Ontario charges peak rates from 11am-5pm, it is the most expensive time to use the air conditioner. During the afternoon, the higher thermostat setting ensures the indoor temperature is still cooler than outdoors, while reducing the energy the AC must expend to maintain the target temperature. As long as the outdoor temperature is higher than 78F/22.5C, it will always feel cooler indoors. This minimizes energy use and cost without completely sacrificing comfort.

5pm: 79 F; 26 C

Ontario switches back to mid-peak rates at 5pm. Meanwhile, this is the time of day when kitchens are creating heat indoors, which makes it that much harder for the AC to keep things cool inside. For this specific period, raising the target temperature can reduce the energy load without a serious reduction in comfort. Also, since the AC is likely to run almost constantly during this time of day, consider that cool air will be circulating throughout the home. Thus, it feels cooler than it really is.

7pm: 77 F; 25 C

At 7pm, off-peak rates start in Ontario and energy is the cheapest to use. The next 12 hours will be the best time to cool the house so it can reset the indoor temperature and get a head-start on the following day.

The AC begins lowering the temperature at this time and it is likely to run constantly - possibly for several hours - which means cold air will be constantly circulating during this period. Because the thermostat turns on the AC to lower the temperature from 79F to 77F (26C to 25C), the immediate effet of the AC is that it starts to feel cool. If the temperature drops too much too quickly, it can even feel uncomfortably cold because the AC just keeps blowing cold air on you. As long as everyone is still awake, it’s usually more comfortable to limit the size of this drop.

Conclusion

If you finished this, congratulations. You now understand air conditioning, what makes you feel comfortable, and how you can program a thermostat to feel good. You can expect that if you reduce your energy consumption - or even merely shift your energy consumption to the night - then you will probably save money. And finally, for those seeking practical and immediate ways to reduce energy consumption, getting control of your home temperature with a programmable thermostat is a great way to start.

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