Systems Run Down

Final few days of tweaking, touch ups and inspections. We spent the morning getting a run-down on our heat pump, HRV and heat-pump water heater. We were able to test all the systems, set the thermostats to the desired setpoints, and listen to the dB of all units indoor / outdoor. Bonus - our Carrier heat pump is nice and quiet 🎉.

We cover HVAC system selection and sizing in earlier posts 11/15/23 and 12/22/23. For more on our heat-pump water heater, read on!

Traditional water heaters either use natural gas or electric resistance heating to generate hot water. It was always our intent to run the house off 100% electricity, so that ruled out natural gas and left us with an electric resistance or heat-pump water heater.

Heat-pump water heaters are fairly new technology but on the verge of going mainstream (Ref: Canary Media). Heat pumps use energy to move heat, not to make it. Like air conditioners, they pull heat from the surrounding air and move it into the water tank with efficiency levels that traditional water heaters can’t come close to.

The metric that measures water heater efficiency is known as the “uniform energy factor” (UEF) 🤓. Essentially this measures how much energy ends up as heat in the water vs. how much comes into the appliance in the first place. The higher the UEF, the more efficient the product. A UEF of 1.0 means zero energy is wasted in the water heating and delivery process. Typical gas and pure electric-resistance water heaters have a UEF of between 0.63 and 0.95. In comparison, heat pump water heaters can have UEF ratings of 3.3-4.1, which translates to 330-410% efficiency! (Ref: DOE).

Our Rheeam heat-pump water heater is a 50 gallon tank with an integrated heat pump and a UEF rating of 4.07. It’s modeled to use around 10% of the home’s energy or ~4GJ/year of a total of 41GJ. An electric resistance heater, by comparison, would use at least twice this amount over the year in practice (Ref: CCHT). This matters for the net zero energy balance.

We will be playing around with all the systems in our first couple of weeks of occupancy and have a chance to refine further.

Up next - the move!