I've seen the Zuba operate at -20C and output 43C. I'd say that is pretty amazing. What's more amazing than that is the fact that the defrost runs for only 3 minutes in roughly 6 hours of heating. I have one installed in my house and I've saved around $700 in heating over last year and this winter is much colder.
I wish i was getting any where close to that with my Zuba system. The installers are now on the way back for the third time this week. My Zuba was installed Aug. 2012 worked good for A/C. but my system does not heat at all! outdoor unit freezes up solid to a block of ice, it is not even below 0c yet and my system just circulates air. I thought it was supposed to defrost, if its a block of ice will the suction pressure not be very low, causing low discharge pressure and there for lack of any heat? The pipes coming in to the indoor unit are both cold, to me there is something wrong. Installers twice now have said the system is working.