Best AC Thermostat Temperatures to Reduce Energy Use and Keep Comfort

You set a number, go out for the day, come back, bump it again, then wonder why the place feels clammy and the meter spins.

This article is about picking a sensible temperature target and sticking with it, plus a few small habits that stop the system from working harder than it needs to. And yes, maintenance matters, even if you don’t want to hear it. Dirty filters, plugged outdoor coils, and half-blocked drains change how the whole thing behaves. If you’re already thinking about booking an AC maintenance visit, you’re probably at the point where the system is trying to tell you something.

We’ll also touch on when a new control makes sense and when it’s just a fancy screen on the wall. If your unit is undersized, oversized, or just plain tired, no amount of “perfect temperature choice” fixes that. Sometimes it really is time to look at a new central air installation and start fresh, especially if comfort has been a battle for years.

So we’ll keep it practical. A couple numbers that work in real Calgary summers, how to handle day vs. night, and why big swings usually cost you more than they save. Well, usually anyway. Most of the time, at least.

Recommended thermostat temperatures for home, sleep, and away hours (with humidity targets)

For “home hours” (you’re cooking, moving around, doors opening), most houses land comfortably around 24°C to 26°C. If you like it cooler, fine, just understand you’re asking the system to pull harder when it’s 30°C outside and the sun is baking the south windows. If you’re doing new heating and air conditioning installations, this is also where proper sizing and airflow make that 25°C feel a lot better than it sounds.

Humidity target while you’re home: aim roughly 40% to 50% RH in summer. If you’re sitting at 55% to 60% RH, the place will feel warmer than it is, and you’ll start noticing window sweat or that “basement towel” smell in corners.

For sleep, most people do well around 18°C to 20°C, sometimes 21°C if you hate cold feet. Bedrooms tend to have weaker airflow, or they’re over the garage, or somebody shut the supply vent halfway years ago and forgot, so you might need a different approach than just lowering the number. The cause is usually duct balance and closed doors.

Humidity target at night: about 40% to 55% RH, with a small caveat. If you wake up with a dry throat, your RH is likely low, but if you wake up clammy, it’s high or your fan is running too much between cycles and re-evaporating moisture off the coil. Also, if your family has allergies or you’re fighting odours, read How can I improve indoor air quality with my AC? because humidity control and air quality issues tend to show up together in real houses, not in brochures.

Away hours is where you can save a lot without making the place miserable when you get back. Set it warmer, usually 27°C to 29°C, and let the building coast. Don’t shut the system off completely in a humid stretch.

Humidity target while you’re out: try to keep it under about 55% RH. If you have a basic humidistat or a smart control that shows RH, use it. If not, at least keep an eye on signs: condensation on windows, musty smells when you open the door, or that “heavy” air feeling that doesn’t go away after the unit runs a bit.

Using schedules, setbacks, and smart modes to cut AC runtime

If you cool an empty house all day, you are paying to chill drywall. Set a simple weekday schedule: let indoor temp drift up a couple degrees after you leave, then bring it back down 30 to 60 minutes before you walk in. That “setback” window is where you save run time without feeling it. Smart modes like geofencing can help too, but only if you actually check the app once in a while. If cooling never kicks back on during a heat wave, people start wondering whether they need a whole new air conditioning installation, and we get it, but schedules usually prevent the panic.

Night schedules matter as much as daytime. Try letting the temperature rise a bit while you sleep, then pull it down just before you wake up, not two hours earlier. If your unit has “auto” fan, use it, constant fan feels nice but it can re-evaporate moisture off the coil and you end up lowering the temp more than you wanted. And please, don’t use massive setbacks thinking bigger is always better. If your place climbs way up all afternoon, the system has to grind to recover and that long recovery run is hard on older gear. That is also when people start asking about an AC replacement because the old setup can’t catch up, or they book our air conditioning repair service after it trips on high pressure from running flat out with a dirty outdoor coil. A small, consistent setback and a sane schedule usually keeps things calmer.