I have a digital space heater. I set it at 84 and it fluctuates +- 2 degrees but it keeps the water in the room a constant temp about 80. You'd have to put it in a smaller room with a door that can shut (like a bedroom). For your room and space heater you may need to set it differently.. you can experiment and see.
I was wondering if one ml. of stress coat+ and 2 drops of prime per gallon of water is too much conditioner? I'd normally just do the prime, but I want to use stress coat for the Betta I was talking about.. The one with his caudal bitten off. (I bought him yesterday afternoon) I'm still waiting to put him in his tank until I finish testing the heater.