We had heat pumps installed by an engineer recommended on this site. He put in Toshiba, fab job. 2 heat pumps in different ends of our small 3 bedroom house. Were lucky we leave all internal doors open and get the heat through the house.
I only wish I had gone for the more expensive model for both as we use the air cleaning quite often in the lounge.
We set a timer for 4.30pm everyday for it to come on and put on low at night when we go to bed and just push it up to 22 in the morning then reset timer for the evening again. The good thing is is you have a sunny day it will only come on if it hits below 22 degrees.
We really noticed the difference straight away, our electric bill halved!! Have not used it in Summer as we used to live in Cyprus so quite used to the heat of NZ.
Get the biggest units you can afford as they have to work less and therefore more efficient. Our house is 120sft.
He ducked ours out of the floor and through a wardrobe so no pipes.