Autumn HVAC Mode from Cool to Heat

Curious how others are switching from Cool to Heat mode now that autumn has arrived.

I created a rule that sets the mode to Heat if forecastHigh < 72 & forecastLow < 52 & season != summer.


We have the problem in Arizona that it can swing back and forth for quite some time. My solution is just to use Auto mode on the thermostat. During the summer my thermostat is just set to Cool, and in the true winter to Heat. But then there's a couple of months on either transition where Auto is needed. I don't try to automate these transitions. It just got cool here yesterday and today for the first time since last spring.

If your thermostat doesn't directly support Auto, you could use Thermostat Controller to give it an Auto mode.

Here in the northeast USA, we are just entering window season again. Cool enough outside at night to open the windows, but still warm enough during the day where the AC is necessary...especially in the later afternoon when the solar heating peaks on the house. Not really worth automating, beyond a "set air conditioner mode to off" to Siri on my Apple Watch as I open the first window every evening.

Our house has oil-fired baseboard hot water heat, and separate forced air central AC for cooling. The heat is hooked up to an Ecobee, and the AC has its own thermostat and also remote/IR control via a Tado. I have given thought to creating automations to use the Ecobee as the only manual control for both the heat and AC for WAF, but the change from heating to cooling doesn't happen often enough to make it worth the automation effort.....

I have an Ecobee 3 thermostat. In the summer, the cooling setpoint is 76 degrees F. In the winter, the heating setpoint is 70 degrees. In autumn, the house temperature is often between 70-76 degrees, so neither the heat nor cooling is required. The thermostat will change automatically to heating mode when the house temperature drops below 70 degrees and will automatically change back to cooling mode next spring when the temperature exceeds 76 degrees.

If you are trying to keep the heating and cooling temperature setpoints close to one another, you have to be careful that you do not end up with a situation that has the AC operating in the daytime and the heater operating at night. That is hard on the HVAC unit and hard on your energy budget. It is better to let the temperature vary slightly so this does not happen. Many HVAC technicians prefer changing from heating to cooling manually to insure that this switching back and forth does not occur.

I cannot recommend settings for you because I do not know where you live, what the temperature variations may be there, and how good your insulation may be. I also do not know what other heat sources you may have from lighting, electronics, etc.

The forecast temperature where I live near Chicago today is for a low of 59 and a high of 68. The current temperature outside is 67 degrees at mid-day, yet the temperature inside my home is 72 degrees, well above my 70 degree heating setpoint. So the HVAC unit is not running. By the weekend, the low temperatures are predicted to get down to 40 degrees and the highs are expected to stay below 70 degrees, so the heat may well come on later this week for the first time this season.

Adding onto @rwclements228 's points. I purposely keep it manual as I don't want to run into a issue where the AC comes on in spring when I may have my AC unit still covered.

I have added a Heat/Cold switch that sets the different set points of the thermostat. I also also have a few other rules that enable/disable based on the season.

Living this problem right now and just set our thermostat to Auto mode. Tucson mornings have dipped to low 40's, but high temperatures will return to 90+F soon. I will be leaving for an extended trip and am confident that my wife would suffer rather than touch buttons. So, I also had to explain to her what will be happening and why.

That is why I made the point about location. Those who live in low humidity areas often see large swings in ambient temperatures between day and night. My daughter lives in the Denver area and sees such swings.

If your home is well insulated, it may be able to contend with a 40-50 degree swing in outside temperature without the inside getting uncomfortable. That is why relying on the temperature forecast to switch from heating to cooling mode might not be wise.

Call me a luddite if you want, but I do this manually. Sometimes I even do it at the actual thermostat. [gasp]

Seriously though, my HVAC has just been OFF for most of the last 2 - 3 weeks here in MN. sometimes the house gets a little warmer, sometimes a little cooler. This morning it was 63 degrees in the bedroom when we woke up. Slept like a baby. I turned the furnace on for a couple minutes to take the chill out and then turned it back off.

I prefer letting the temperate drift to the extreme ends of my comfort range so that I can keep the windows open and heat off as long as possible. Saves energy this way, too.

That said, I understand that this isn't practical for some people or some places. If I had to do something automatic, I would almost certainly NOT use outdoor temperature as a deciding factor. As others have noted I would just use the auto setting on the thermostat and set a nice, wide range between heat and cool.