I was very confused about the heat pump when we moved here. Thanks for that explanation, KelvinAng.
I was under the impression in the US that a "heat pump" was pumping heat (hence the name) from the earth through deep piping that moved water (oil?) up and down. I think the piping goes something like 50 meters into the ground--where the temperature is constant all the time. These systems are VERY expensive ($30,000 and up)
So I was confused to find the NZ heat pump is basically like the little heaters/ac units they have in cheap motel rooms. They will heat/cool a tiny motel room but not your whole house. Air sourcing seems silly and inefficient.
We froze our butts off in our first rental. It was awful. I ran the heat pump 24 hours a day and used 2 oil heaters 24 hours a day. We were NEVER warm.
But now we are warm and cozy with a new home with modern insulation and double glazing. The house is passive solar and I never turned ANY heat on during sunny days over the winter.
I rarely used anything on cloudy days either as I have learned to be cold (and cheap!!) the kiwi way.