Saving energy at home starts with reducing heating costs, by far the biggest energy eater for most U.S. residences. In the Midwest heating typically accounts for more than 70 percent of utility expenses.
Although heat pumps need electricity, which is responsible for 25 percent of carbon emissions in the U.S., those emissions are lowered drastically by the increasing use of renewable energy sources like wind and solar. Heat pumps are also highly efficient, using less energy overall to produce the same level of comfort in a home as compared to a combustion-based furnace.
Even in areas of the U.S. where electricity is predominantly generated by burning natural gas or coal, heat pumps are still cleaner and more affordable than furnaces. Research has shown residential heat pumps can reduce carbon dioxide emissions by 38 to 53 percent over gas furnaces, depending on the region. A widescale switchover to heat pumps would also eliminate a lot of leaky fossil gas pipes and fittings, large sources of methane pollution, a greenhouse gas many times more powerful than carbon dioxide.
Do heat pumps require a back-up heat source?
Heat pump technology is rapidly evolving. Cold climate heat pumps can function efficiently even in subzero temperatures. Other models lose some efficiency as temperatures drop but can still maintain heat in the home. Although we experience a handful of negative-degree days each winter, the average winter temperature in Iowa City is 26 degrees and trending warmer.
For those new to heat pump technology, replacing an aging air conditioner with a heat pump can be an effective way to explore whether or not to retain a back-up heat source. The heat pump will cool the home just like an air conditioner in summer, and in winter it will work with the existing furnace to provide heat for the home. When it comes time to replace the furnace, the household can decide to rely entirely on the heat pump, supplement it with another type of electric heating like baseboard units, or replace the furnace based on how the heat pump performed in previous winters.
Some residents in Iowa City rely solely on heat pumps for their heating and cooling. Others have opted to retain a back-up heat source. Ultimately the choice to have a back-up heat source is a personal one based on comfort with the technology and what works best for your home.
How do you choose a system?
Heat pumps generally fall into two categories, ducted and ductless (sometimes called “mini-split”) systems. Ducted heat pumps consist of an outdoor unit, and indoor unit, and ductwork to help move heat throughout the home. For this reason, households with existing ductwork system often opt for a ducted system. This type of system is also most compatible with a dual-fuel system that used a forced-air furnace as a back-up heat system.
Homes without an existing central heating and cooling system often opt for a ductless heat pump system, which consists of an outdoor unit and one or more indoor units mounted to the wall, ceiling, or floor. These systems can be slightly more efficient than ducted systems, as less heat is lost in the process of moving it through ductwork.
Regardless of the type of heat pump you choose, it is important that it is sized correctly for your home. Bigger is not always better, nor are cold climate heat pumps always the best choice. An oversized or overpowered system can be costly and reduce the financial benefits of using a heat pump. An experienced HVAC contractor trained to install heat pumps can calculate the correctly sized system for your home. Getting multiple quotes can give you assurance the calculations are correct.
What about refrigerants?
Like air conditioners, heat pumps utilize refrigerants to help capture and move heat. When released into the air, these refrigerants can be powerful greenhouse gasses. The most common source of refrigerant leaks are old and poorly maintained units. On balance, though, heat pumps are still less harmful to the atmosphere than furnaces, and better refrigerants are being developed to power these systems.
