I found this while snooping around on the internet. For those of you who keep hearing about heat pumps but still know nothing about them, this is a pretty good visualization.
A fridge but in reverse? The fascinating science of heat pumps – visualised – The Guardian (newspaper in the UK)
…except that boilers are certainly not the norm here in western Canada. Substitute boiler with heat exchanger.
So I’ve had a heat pump at 520 for over a year now, and it works well. To be honest, though, we still haven’t had much of a winter yet this winter. If / when it ever gets down to -40°C, then we’ll actually put it to the test.