Changing to Heat Pumps

We live in Canada at 54 degrees north and are in Winter 5 months of the year, see temps as low as -30C.

Our gas hot water heater is 16 years old and while we aren’t having any issues with it yet I wanted to be proactive and change it on my schedule, not as an emergency in the middle of the night.

We have a Solar Panel system that’s generates about 8000 kWH/year, our current consumption is about 5000 kWH/year.

I would like to migrate away from gas and put in an electric heat pump water heater and a heat pump/electric furnace. Does anyone have any experience using these in colder climates and know what their power consumption is.

We are looking at the Rheem Prestige 50 gal. Have not done much research into home heating yet.

Thank you!

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Here in Northeast Ohio, I exist with all gas appliances. Heating with gas is warmer, compared to electric. Shifting the utility costs from gas to electric wasn’t beneficial, absent a solar presence.

I anxiously await your findings, given your solar augmentation!

Home heating via a heat pump with -30C outside is pushing it. i.e. won’t work.
The Mitsubishi HyperHeats will operate down to about -25C in heat mode but at significantly reduced efficiency. I’m not sure Mitsubishi (or others) even publish efficiencies at or near the operational minimum temp. The M-Series go from a COP of around 4 at 8C to 2.5 at -8C.

That said, on less than brutal days a heat pump (especially with solar) will save you a ton of energy. The most efficient workable non-fossil combination would probably be that plus a pellet stove to augment/takeover when the temp drops. Apart from a well-insulated house, the real key to efficiency is to have some form of thermal mass inside that you can heat at the optimal time, especially when the sun is out. The Germanic approach is to use as much hot water storage as possible. Posted this before but it’s always entertaining …

A heat pump hot water heater will certainly be more efficient than a regular resistive-element one. However, depending upon how you duct things it could be sucking the heat from your house in winter … so then the efficiency depends upon that of your house heating. You could duct it to the outside selectively when the outside temp cools down, but nowhere near -30C. In summer it gives you “free” cooling.

The most efficient heat pump water heater, and the most ozone-friendly one as well, is the Sanden SanCO2.

I’m in the SF Bay Area, so can’t speak to its cold-weather performance. They claim it works at -26 C and below. It might not work where you live, but I’d definitely investigate it if you’re still deciding on how to proceed. It’s fantastic equipment and technology.

The CO2 refrigerant in the Sanden is a great plus but the EF, I suppose as a consequence of that, is not as good as competitors from what I can see from the published numbers.

Unless I’m missing something, another aspect of the Sanden configuration is the lost chilled air in summer months. It seems like a good larger scale solution if noise, refrigerant production & leaks (and all that that implies) is your main concern.

I live in Burlington, Vermont and have a Rheem Prestige 50 gallon water heater. There are just two of us in our house and we run the dishwasher every day. According to my Sense stats based on the last 30 days, the unit will use 265 kWh per year. Previously I was using a 40 gallon gas water heater that cost over $200 a year. The Rheem will cost under $50 a year! The estimate on the Energy tag was around $100, but perhaps that was for a family of four. So your solar panels will cover it just fine. Outside temperatures shouldn’t make too much of a difference since your unit is inside the house. Hope this helps!


The gotcha I pointed out above is that if you are using a heat pump to heat your house in a cold climate, unless that heat pump is significantly more efficient than your hot water heat pump, you are taking “solar heated air” and essentially re-pumping it to heat your water. Meaning: In that situation, in winter, you are better off trying to duct the hot water heat pump to the outside.

That said, most high end house-heating heat pumps are much more efficient than the hot water heating variety.

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