Automation that sets heating and cooling depending on forecast

Surely this exists already right?

At (time), check the weather forecast. If the forecast is above X then turn on cooling, if the forecast is below Y then turn on heating.

Seems like simple logic but I can’t find a blueprint that does it. Could somebody point me in the right direction?

I’ve been thinking about this topic, and it appears to be pretty complex. Temperature and humidity changes have an immediate effect - depending on sunshine/cloudiness and on humidity, but also a delayed effect. The delay depends on insulation and mass (there’s some term for it). The heating system itself has a lag, depending on how it works and the mass of the building; compare massive concrete floor heating with direct air heating. The system is hard to create, and each building is unique, so generalizing is even harder. Then you might decide to turn on the sauna or the fireplace, or cook some food - further complicating the system. I would also like to base the target temperature on the electricity price for the coming hours.

I wonder if the characteristics of a building can be inferred from outside/inside temperature history and electricity consumption. All consumption contributes to heating. Cooling would flip this upside down.

I think you’re overcomplicating it.

All I want it to do is look at the day’s forecast temperature and either heat or cool.

Haha, that’s probably true, but in that case you are too :slight_smile: . You can look at current inside temperature and decide whether or not to heat or cool. If your heating system has enough power, it can react faster than weather ever changes. Anyway, in my case, the case for predictive heating is to spend electricity when it is cheaper, and avoid when it is more expensive. It changes by the hour. By looking forward, I could heat my home a little extra when the prediction is that more heating is necessary in the next few hours and the price will rise, and a little less when the price will drop and temperature forecast allows for it. However to do it properly, I must figure out at least the natural lag of my house. I already know the base consumption, which is about 1kW, which heats the house about 13 degrees over the outside temperature. The more granular one wants to get, the more aspects must be taken into account. If it was simple, we would have this figured out by someone else ages ago.

I’ve been thinking about doing this but with the fan. If the high outside is, say, 75 I dont need to circulate air to keep the different levels even but if its hotter I do.

If forecast is above x or below y temperature run HVAC fan for next z hours.

I appreciate you replying to my post but I still think you’re overcomplicating it.

I have rarely in my life experienced a case where the weather forecast in the morning was not pretty close to accurate for the day.

All I really want to do is have it poll the weather service for the max temperature predicted. If the max temperature is above a certain value, turn on cooling. If it’s below that temperature, turn on heating. The air conditioner units themselves regulate the temperature on their own.

In reality it is a complex system. I’ve been thinking of this and will probably take a stab at it - that’s why I’ve tried to get to the bottom of it and understand what’s going on. If the model (in my mind) doesn’t represent reality, I will fail without knowing why, or at least end up unsatisfied. I agree that a very simplistic system can reap the lowest hanging fruits, but the engineer in me wants to do it properly. It can still be represented to the user in a simple way.

Why exactly do you want a predictive system? Is it to have a more stable temperature inside?

I found this thread as I’m looking for something broadly similar (but not the same).
I haven’t found a blueprint that does this either. However, the automation to do this is relatively simple and would only take a few minutes to set-up.

My interpretation of the requirement is:
At time X, look at the forecast temperature.
If forecast temperature is > Y then turn off heating and turn on cooling
elseif forecast temperatuer is < Z then turn off cooing and turn on heating

Assuming the heater and cooler have their own thermostats then this will serve to control the room temperature. If there’s no thermostats then the room temperature will likely be very unstable due to over-cooling/heating.

It needs weather forecast data. Getting data from the OpenWeatherMaps integration is easy and will expose sensors with forecast data. Create a simple automation in the GUI to use the data and switch devices on/off.

@nilux I agree, getting the HVAC to provide “perfectly controlled” heating and cooling is very complex and unique to every room in a house. Thermal inertia, solar gain, wind chill, ambient temperatures, energy losses through roof & walls & floors & windows, heat transfer coefficients… etc. “should” all be taken into account. I am looking at this just now for storage heater control in my house. I envisage an “energy balance” approach where I calculate the gains/losses in the room and calculate the energy required to input to the storage heaters to balance the heat loss.
I need a predictive system as the storage heaters only charge up at certain times of night & day. If tomorrow is going to be warm and sunny then I don’t want the heaters to charge up unnecessarily tonight.
If anyone has any experience or links to share I’d be super grateful.