It depends on the climate in which you will place your tiny house. We typically recommend mini splits for both heat and AC. However, if you are off grid this is not as good of an option. If you live in a very cold climate, you may want supplementary heating sources.
Most climates in the US are okay. We use energy efficient Pella Windows which are energy efficient. For supplemental heat we can install a propane marine heater or a wood stove.
Just let us know where you will put your tiny house and we will advise you with several options and their respective prices.