All Herschel Thermostats can operate without wifi.
Using wifi makes the controls easier to use and enhances the range of control features available to you (like linking with a PIR sensor; Voice Control or Group Control of multiple thermostats). It also allows you to manage your thermostats while you are away from home.
But all our thermostats will work as thermostats (i.e. turn heaters on if it is too cold and turn them off at the correct temperature) without wifi.
Specific wifi-free operation varies per controller:
Without Wifi, T-PL; T-MKS and T-MKS operate only in manual mode (i.e. manage to a fixed set temperature only).
All other thermostats (T-BT; T-MT; MD2; T2/R2) offer a full weekly schedule of 4 programs a day.
T-BT is not wifi enabled.
What if wifi fails while my thermostats are connected?
Should wifi be lost for whatever reason while your thermostats are running, then:
T-MT, T2/R2, MD2 will run with the locally stored schedule.
T-PL, T-MKS, T-MKW will continue running the last set temperature.