Heat Pump Water Heater in Cold Climate
Living in a northern climate, I can’t understand if it makes sense to get a hybrid electric/heat pump water heater for my house. My house is a split level design. The lower level is always colder than the upper level because it is half underground. This is the level that we have an unfinished utility room (housing the water heater) as well as our guest room and the large rec room where we watch tv in the evenings. Since we already struggle keeping the area warm enough in the winter to be comfortable, I am concerned that the hybrid water heater would add to this challenge. But I am really interested in energy efficiency so I want to make sure I fully explore this before I write it off. Can anyone offer some guidance?
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Read this post by Alex Wilson: Heat-Pump Water Heaters in Cold Climates. He addresses your concern around comfort, saying: "In a typical New England [cold-climate] house that has a furnace or boiler in the basement producing a lot of waste heat, a heat-pump water heater can use some of that waste heat and it’s not very noticeable. The less efficient the heating system, the less noticeable is the effect of the HPWH.”
If your main heating system is already struggling, you could turn the hybrid tank into electric-only mode for the cold months. It wouldn't be nearly as efficient but it'd still be good for the other 8-9 months out of the year.
You're really asking two separate questions here.
A heat pump water heater takes its heat from the heating system in winter. Whether that is a good idea depends upon what your heating source is and what your alternative is for heating water. If you're all-electric it usually makes sense. If you have natural gas probably not, at least from a financial perspective. But keep in mind that in the next 30 years or so we're going to have to stop burning fossil fuels on an individual basis. We're starting to get to the point where within the life expectancy of equipment being installed today we're going to have to be all-electric.
The second question is that the lower part of the house has trouble maintaining a comfortable temperature. This means your heating system isn't putting out enough heat to make up for heat losses. You either need more heat or less loss (ie more insulation). It could be as simple as balancing your ductwork. Yes, taking heat out of that part of the house without doing anything will make the problem worse. But that's not a flaw of heat pumps.
Thanks - you are right this is two separate problems and I appreciate you calling it out as such. We are planning on installing solar panels within the next 6 months so switching from our natural gas water heater to an electric seemed like a no brainer. But realizing how much energy that actually uses in relation to how much we can produce (based on shade and our rooftop angles we estimate that the electric water heater would use up to 50% of our annual energy production), makes it more of a question mark for me.
As for the other part of the problem, we just had a heating specialist over and all they did was open the dampers more to let more air into the lower level from the upper level and that has had minimal impact. But I suppose that might be worth more investigation.
If solar produces 50% of your annual energy usage, then the question is which 50%, and what produces the rest. I assume the answer to the second question is natural gas in your case. Water heater might be a good candidate for part of the 50% though.
A side benefit of a heat pump water heater is it assists with the cooling in the summer and dehumidifies.