Heat Pump Water Heater

Heat Pump Water Heater, Installed

As part of our upgrades to the heating system in our house, including replacing the gas furnace with an air source heat pump system that could both heat and cool, we also swapped our old gas water heater for a new air source heat pump water heater, complete with Wi-Fi connectivity and and app.

Our gas fired water heater, although only ~15 years old, was something of a dinosaur in design terms, complete with a pilot light and thermocouple based thermostat that only had the mysterious values ‘A’, ‘B’ and ‘C’ marked on its temperature control. It was never clear what temperatures those represented, and, not surprisingly perhaps, the actual water temperature varied.

The new unit, from Ruud, is part of their Professional Ultra Series and includes access to Rheem’s EcoNet online controls. Ruud is part of the same company as Rheem, and it seems these units are essentially the same as Rheem ones – Rheem is the more consumer oriented brand, sold through retail stores like Home Depot, and Ruud is sold only to contractors.

From the app, we can control the settings of the water heater, but we can also monitor how much electricity is used by the hour, or day (as well as show weekly and monthly usage charts) which will be useful for estimating cost. There is also a scheduling capability, which will be useful for those on time-of-use plans.

The tank is officially a hybrid water heater since there are two resistive coils in there as well which it can use if necessary, assuming they are enabled. The tank has various modes allowing you to choose between heat pump, resistive coils or both, as well as what they describe as ‘eco mode’ where it will use the heat pump most of the time, but can use the resistive heating elements if needed.


In terms of plumbing, the unit installed pretty much the same way as the gas one we were removing. The only differences being a new line was required for the condensate to drain outside the garage, and the cold water feed enters the tank at the bottom instead of at the top, necessitating the long drop of copper pipe shown in the photo.

The big difference comes from the need to have a 30A 240V circuit to power the unit. For us, that meant running a new line from our main panel into the garage (diagonally opposite each other), but our electrician came up with a novel solution and used the old flue pipe as the cable conduit to drop the wires from the attic down into the garage right next to the water heater.

In Use

The controller on the tank is functional, but certainly not going to win any awards for ease of use. It reminds me a lot of the old style thermostats that were fitted in the house when we bought it; they worked, but they were a pain to program and were obviously designed to be set and forgotten.

In comparison, the EcoNet app is actually very well designed and much more modern in its presentation. The main control screen for the app shows the current state, the selected temperature, current mode and provides navigation for the various options.

The usage screens show current day in hourly slices (or week/month/year in appropriate slices) as green bars, but they also overlay the previous day’s (or period’s) data as a dotted line with points, letting you compare periods really quickly.

Also included in the app is a health check screen, showing the health of both the compressor and the heating elements, and the scheduling capability should you want to try to optimize based on a fixed schedule. The scheduling can be set based on day of the week (useful for those, like us, who have TOU rates that include weekday peak periods, but no restrictions on weekends).

There is also an Alexa integration, but currently it only allows the unit to be turned on or off, which is of limited use.

Perhaps the most important part of the unit in use is how well it delivers hot water. We have the unit set to 120℉ (49℃), which is plenty hot enough for us, and is also the “safe” temperature recommended by the app and by our pediatrician every time we go for the kids’ annual check up. The system has had no problem delivering that for showers even with all four of us. The tank we have is slightly smaller than the previous gas one was (65 gallons compared to 74 gallons), but it is still plenty for us.

Our garage is noticeably cooler too (the unit is drawing heat from the garage to heat the water), but not cold enough to be a problem. It is also being dehumidified, but again that is not really noticeable. The only noticeable change is when you go into the garage while it is running, and then you can hear the compressor and fan running. You can feel cool air from the outlet fan on the unit as well.

Outlet Fan


As with the heat pump based central heating/cooling, there are rebates available for heat pump water heaters too. In our case, BayRen has rebates on the water heater in addition to rebates from our local electricity utility in Alameda. Check your area to see whether there are rebates available, which will bring the cost of switching to one of these units down a lot. In our case, even with the more expensive unit and the cost of the wiring, after the rebates we should end up paying what we would have paid to just replace the gas unit. Whether we will see cost savings from the unit remains to be seen as my best guess as to how much we were paying for the water heater before was very low too. The zero carbon aspect as well as the smart controls make it well worth doing though, even if it costs slightly more.

Tank vs Tankless

While not an option for heat pumps, since they are not capable of instantly heating water, we did look into tankless options, both gas an electric. Our research suggested that the running cost of the heat pump systems should be lower than an electric tankless, and, while running costs for gas tankless were similar, the additional maintenance recommended for them would make them more expensive. They were both around the same price to install as the heat pump systems, but lacked any rebate options.

Finally, and this was not something we had considered before doing the research, having a 65 gallon tank of potable water in the garage can come in useful if we have a large earthquake which disrupts drinking water supplies.

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