When thinking about energy-efficient heating and cooling, heat pumps quickly become part of the conversation. Heat pumps are commonly used in well-insulated new builds and therefore also commonly used in Passive House buildings.
There is no doubt heat pumps are saving on energy and reducing your carbon footprint when compared to conventional heating and cooling systems. But when researching the topic in more depth, there appears to be some confusion about heat pumps counting as renewable energy...
What is a heat pump?
In basic terms, a heat pump extracts heat from one side of the system and transfers it to the other side of the system. One side of the system represents the outside of your house, the other one the inside. Such a system can operate in just one direction or both depending on the system and the season.
There are different types of heat pumps available for residential applications:
Air-to-air heat pumps, used for heating or cooling the air inside your home,
Air-to-water heat pumps, used for heating your house via hot water supplied to radiators or an in-floor heating system, or used to heat your domestic hot water for faucets, showers, laundry, etc.,
Ground-source heat pumps (or geothermal heat pumps) that we have blogged about in a previous post, and sometimes
Water-source heat pumps.
Ground-source or water-source heat pumps can be used to either heat air or water.
We recommend checking out this video for a good technical overview of the different types of heat pump systems.
What counts as Renewable Energy?
Heat pumps are often labeled as "sustainable", "green" and when you search online often also as "renewable energy". Some of the confusion lies in the fact that none of these terms are standardized.
Renewable energy sources generally include resources that are replenishing naturally, like the wind, sunlight, flow of water. So far so good, because you can clearly argue that the heat trapped in the outside air, ground, or water is generally available and being replenished by Mother Nature.
But that's not what's going with heat pumps! Heat pumps require electricity to operate. It's needed to run the compressor and the pump(s) and ventilator(s). The requirements a heat pump has on external electricity are similar to other heat exchange systems, let's say a conventional air conditioner or your refrigerator. These devices cannot be called "renewable" by any stretch, and the heat pump should not be labeled as "renewable" either.
Where is the confusion coming from?
We believe three reasons contribute to the potential misunderstanding of heat pumps as a renewable energy source:
Heat pumps are often associated with geothermal energy production. The term "geothermal" leads people to think of geysers or natural hot springs. This very same phenomenon that's causing these beautiful hot pools in places like Iceland is used in industrial-scale geothermal energy production where steam turbines are used to produce energy or heat. Ground-source heat pumps are also known as geothermal heat pumps that draw energy from underground, but this terminology doesn't make them renewable per se.
Heat pumps are highly efficient compared to conventional heating and cooling systems. When calculating this comparison, the energy savings typically outweigh the input required to operate the heat pump. This makes them so beneficial.
There is no external fuel that's needed to operate a heat pump. You don't need any natural gas, wood, oil, or other fuel to operate a heat pump. Yes, some electricity is required as mentioned above, but there is no additional fuel source needed beyond that.
These reasons may lead to some misconceptions overall, especially when it comes to the marketing of this technology and online resources.
Where does this leave us?
So, heat pumps do not count as renewable energy. But this is not as important as understanding the basic principles of the technology and its benefits to you as a homeowner. There are many excellent applications for heat pumps in residential construction. Some houses even have multiple heat pumps, either for heating and cooling different areas of the house, or one heat pump for heating and cooling and another one for domestic hot water. At the end of the day, these appliances are very efficient and there are good reasons why some countries even incentivize them.
Where the lines to renewable energy get a little more blurred is when heat pumps are combined with renewable energy. This happens frequently in very energy-efficient home construction, including Passive House. Two of the use cases are
A parallel installation of a solar system that produces electricity. Here the electricity produced by the solar system powers the heat pump (amongst other things), which offsets the energy demand from the heat pump and creates a possible "net-zero" or even "net positive" energy effect.
A combined thermal solar and heat pump system; called "solar-assisted heat pump". In this case, the solar system produces hot water that either goes straight to the hot water tank or the evaporator of the heat pump. Both devices act in unison and optimize hot water production (for heating or domestic use) in varying environmental conditions.
Whatever the use case is, heat pumps can be a good and energy-efficient alternative to conventional heating and cooling systems. Mechanical designers and contractors are familiar with the technology and can help you make the best decision for your home.
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