Which thermistor or temperature sensors are less power draining?
There are various way to approach the problem… an NTC/PTC has obviously as load its value at the temperature of interest (usually around 10kohms but even more depending on the model)
Active temperature sensors vary wildly: the almost overused LM35 needs about 100µA to work and gives an analog voltage, the TMP05 has a 600µA active mode but can be put in standby at some 10µA (output is a pulse duration by the way).
And now the most important trick of all: just power off the sensor when you don't need it. Even a PT100 RTD (which is a 100 ohm resistor, more or less) consume almost no power if you power it up only, say, every 5 seconds (depending on the application)