Just as the winter set in, my heat pump failed.
The HVAC technician who came to diagnose it found a leak in the coils of the air-handler (interior) unit. Sadly I don't believe I have any documentation or a warranty.
Of course, when it failed I plugged in a space heater and somewhat to my surprise this single space heater has managed to heat the entire house all winter. In fact, if the outdoor temps get up to the mid 40s I often wind up turning the space heater off for a few hours. It has been a mild winter, with nighttime temps rarely dropping below 15°F.
I measured the power consumption of the space heater and it's drawing 1100 watts. My aquarium draws another 300 watts averaged over the course of the day.
Overall, a nice testament to the energy efficiency of the house.