Bug in the way heating activity is calculated
According to Tado's app my heating system has been on for 20h per day on average during the last month, and 24 full hours the day before yesterday. In reality my boiler has been on for only about 10 minutes the day before yesterday, and the same goes for the rest of the month.
The reason for this funny discrepancy becomes obvious if you look at the top heating areas in the house: Out of the top three only the Living Room (the third) is attached to the zone controller, and thus has the ability to call for heat and turn the boiler on. The radiators in the two other areas (Toilet and Bathroom) are independent radiators that can only piggy back on the heating system when the boiler is already on due to other requests.
This mode of calculation has been historically messing all the numbers in my Tado app, and it won't surprise me if the servers make wrong decisions or suggestions based on these erroneous data.
It would be much more useful if the app could report the real on time of the system, which is a much better proxy for the actual energy consumption, or at least give us the choice.