How a heat pump copes with an Ottawa winter
A heat pump moves heat instead of making it. In summer it pulls heat out of the house like an air conditioner. In winter it runs the other way and pulls heat out of the outdoor air, even well below freezing. Cold-climate models are built to keep going through a January here.
The colder it gets, the harder a heat pump works and the less heat it puts out. That's why most homes keep a second source of heat for the coldest nights. Ontario's Building Code uses −25 °C as the heating design temperature for most of Ottawa and −26 °C for Orléans, so whatever you choose has to cover that night.
Hybrid: a heat pump with your gas furnace
In homes with natural gas, the common setup is a ducted heat pump paired with a furnace. The heat pump heats and cools through most of the year, and the thermostat hands off to the furnace when it gets colder outside than a set temperature. You keep gas heat for the cold snaps and burn far less of it the rest of the time.
Ductless for rooms the ducts don't reach
Mini-splits suit a finished basement, an addition, a room over the garage or a home with no ductwork at all. A small line set runs through the wall to a slim indoor unit, and one outdoor unit can serve one room or several.
Ice on the outdoor unit
Some frost on a heat pump in winter is normal. It clears it with a defrost cycle, which can send up a cloud of steam and sound strange the first time you hear it. A unit that's encased in ice, isn't defrosting, or is being dripped on from the roof edge needs a technician.
Rebates
Ontario's Home Renovation Savings Program, run by Save on Energy and Enbridge Gas, has offered rebates on qualifying cold-climate heat pumps. The amounts and rules change, so check saveonenergy.ca before you buy.