People have successfully owned/bred Sulcatas all over the world. You really want to try and keep the winter house above 60-65 degrees during the winter. A lot is trial and error at first but you will find something that works best for you. I live in AZ so the coldest nights we get are around 35 degrees and I have a space heater hung inside their tort house which has flaps to keep the draft out. I have a thermometer that I place inside to get a reading 24/7. The space heater also has it's own built in thermostat so it turns off when it reaches 80 degrees during the winter. My Sulcatas will go in/out as they please. I do daily checks on them which include monitoring the heater and making sure everything is safe and working correctly--I also do one nightly check to make sure both torts are inside at night and out of the cold. I have separator built in between so this keeps the bigger gal away from my smaller one.
This is their winter house which has an entrance to the front and back--they are blocked from each other for safety reasons.

I have tried heat lamps but find the space heater to be much more practical and in my opinion a lot safer!! I stayed away from the heating mats only because I was told that when a tort sits on a heating mat for hours and hours it can turn into a nesting site for parasites. But I've also talked to a few people that love the mats, I just found the heater to work ideally for me.