Yeah, heat pump water heaters don't use any outdoor air. There is no combustion or anything going on. Think of them as kind of like a reverse-refrigerator. Your fridge takes heat from the contents inside the fridge and dumps said heat into your kitchen. The heat pump water heater takes heat from your mechanical room and dumps it into the water inside the heater vessel.
Heat pump heaters are a great idea in warmer climates, because they essentially work like an air conditioner that dumps the heat into your water rather than dumping it outdoors at a condensing unit. In more humid climates they tend to be very helpful in keeping the basement dry too, as they act just like a dehumidifier.
In our climate we need to add heat to our houses most of the year, meaning it's taking air you've already had to heat up to keep the house warm and dumping it into the water. Your water heating system is essentially robbing Peter to pay Paul, making making your space heating system work a little harder. It also dries out your already arid basement even further, meaning your humidifier needs to work harder.
As such I think they're a crappy solution for the average Albertan.
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