Which Heat Pump Water Heater to Use?

In many applications the heat pump is a huge advance over other options for heating hot water. Now GE, Rudd/Rheem, and Stiebel Eltron have competing water heaters on the market. Both allow you to shut off your oil boiler for 6 months a year, and reduce the need to run your dehumidifier.

To Make a decision, first it’s important to understand a little bit about how a heat pump works. All heat pump water heaters on the market are hybrids, which means they have resistive back up in case the heat pump alone can’t keep up with the hot water demand. The reason for this is that the Heat Pump, by itself, is slow to make hot water. However, the heat pump is between 2 to 5 times more efficient than resistive electricity, depending on the temperature and humidity of the room (they run more efficiently in warm moist conditions).

The resistive element is located about 1/3rd down from the top of the tank. That means that when cold water has reached the top third of the tank, the electric element will kick on, and the efficiency of the heat pump will drop significantly.

GE Heat Pump Water Heater

The GE Heat Pump

When GE designed the heat pump they had primarily in mind to make the units interchangeable with electric water heaters. With this goal in mind, they kept the volume down to 50 gallons, and the insulation down to two inches. It has two 4500 watt electric elements built into the tank, just like an electric water heater. The beauty of the GE heat pump is that it will fit in most any space, it’s easy to install, and it’s elegantly designed. Another nice feature of the GE Heat Pump is the fact that it can be set to one of three modes; heat pump only, heat pump with the upper element, or heat pump with the upper and lower elements for times of high demand.

The drawback of the GE heat pump is that, given its small size, it is likely that during periods of high demand, either the resistive electricity will be used, or it will run out of hot water. For larger families, this will often be the case. The GE heat pump water heater installs for about $2,500.

Stiebel Eltron Accelera

The Stiebel Eltron Heat pump is designed to never or rarely need to switch to resistive. It has the highest energy factor of all of the Heat Pumps listed on the Energy Star web site. It has more insulation around the tank, and, most importantly, with a capacity of 80 gallons and a setpoint of 140 degrees, there is effectively 100 gallons of hot water waiting, so it is very unlikely that it will ever switch to resistive mode.

Stiebel Eltron Heat Pump

Because of its larger size and higher efficiency, the Stiebel Eltron water heater is both more expensive to purchase and more expensive to install. Stiebel Eltron Heat Pumps install for about $3,000.

Summing it up

We tend to recommend that people with larger families, larger homes and enough head room in the basement, go with the Stiebel Eltron Heat Pump water heater over the GE. Resistive electricity is no way to make hot water, and, with the GE model, larger families will find themselves doing just that. One or two people will do just fine with the GE, and save some money on the installation.

In any case, a heat pump water heater that shuts off the oil boiler 6 months a year, and lets you throw away your de-humidifier is a great investment.