A lot of time and energy is focused on geothermal energy to heat and cool your home. This is very important, and in almost every home is the largest contributor to energy costs. However, another large energy user in a home is the heating of domestic (potable) water. This is where Heat pump water heaters come to the rescue! What if the same geothermal energy that is used to heat your home could be adapted to heat water as well. Is there a way to use highly efficient equipment to make water warm?
Heat pump water heaters use the same technology as geothermal heat pumps but apply energy to heating water instead of heating air. The water heater can pull in warm air to heat water and/or water that comes from the ground loop. The same piping (buried geothermal piping outside) that is connected to the HVAC equipment in the building can be connected to the heat pump water heater to heat domestic water. Some use one of these options, but many use both.
Are Heat Pump Water Heaters More Efficient?
The short answer is yes! They do not use combustion (such as natural gas) or electrical resistance heat to heat water, both of which are inefficient processes. Heat Pumps are more efficient heat transfer mechanisms than most conventional types of equipment. They have higher performance and fewer by-products. In fact, lots of residences have gas powered water heaters as their sole gas connected device. Using a heat pump water heater would eliminate this utility connection entirely in this case.
One of the most efficient uses of geothermal to heat potable water is the condition where the building needs to be air conditioned but domestic water needs to be heated (showers, sinks, etc.). The main heat pump(s) are in cooling mode, where they are bringing in water from the ground loop and running it through the heat pump. When the heat pump is in cooling mode, it blows cool air to the building, but this creates hotter water in the geothermal loop. Hotter water in the geothermal loop is actually better for the heat pump water heaters. They bring hot water in, transfer that heat to the potable water, and then place cooler water back in the geothermal loop. This water is what goes outside into the ground loop to stabilize temperature. You see, these systems can work together to increase efficiency of the WHOLE system by using geothermal water at optimal temperatures.
Does a Heat Pump Water Heating System Require More Equipment?
No. If you already have (or are thinking of installing) a geothermal HVAC system, you will already have a pump that circulates water through the geothermal loop. These pumps are typically large enough to provide water for domestic heating purposes. The system will utilize a storage tank similar to gas and electric powered water heating systems.
You might not know this but every water heater, whether it’s gas, electric, or geothermal has a small device called a thermocouple inside the storage tank. This thermocouple serves the exact same purpose as the thermostat in your house or office. You can set it to a certain temperature and it is what controls whether the water inside is too warm or too cool. A water heater, no matter the source, will control to that adjustable set point.
I’m on the Fence, is it Worth it?
Each person has to make up their own mind on this, but I cannot imagine installing a heat pump system to heat and cool my home or office building without including the ability to heat water. In most cases, it does not increase pipe sizing or pump sizing. In several cases it eliminates a natural gas connection to your building. Also, water heating costs are typically the second highest contributor to the average residential electricity bill behind HVAC. If you are installing a system that will operate more efficiently than every other alternative, why not spend the money to replace a gas or electric water heater with a heat pump water heater?
The bottom line is you should do it. You will make your two most expensive energy users more efficient by adding very little system capacity. Heat pump water heaters are certainly a compliment to the larger geothermal system. However, installing both will have large impacts on your utility bills and you will save more money over the long term.