What is a heat pump?
Heat pumps are the latest and greatest heating technology to meet the heating and cooling needs of your building. Heat pumps are clean and efficient heating systems which use electricity to efficiently transfer heat from outdoor ambient air into your home.
How does a heat pump work?
Heat pumps transfer heat using a compressor, an expansion valve, and a refrigerant. Much like how a refrigerator uses a compressor and a refrigerant to cool the inside of your refrigerator or freezer, a heat pump uses the same process, but in reverse.
The compressor is responsible for heating the refrigerant. At the beginning of the compression cycle, the cold refrigerant enters the compressor where it is heated and turned into a high-pressure, high-temperature vapor. This vapor is pumped into an air handler in your home and the thermal energy is then distributed via a fan in the handler.
The refrigerant next passes through an expansion valve, expanded in volume, and cooled back into a low pressure, low temperature, part liquid, and vapor mixture. This mixture is pumped outside to the outdoor heat exchanger where it collects new outdoor thermal energy to repeat the cycle.
How can heat pumps help to lower my heating bills?
Heat pumps are extremely efficient at moving heat. Because heat pumps simply transfer heat from outdoors to indoors, and do not create heat, they can achieve efficiencies of up to 250% to 350%. Another way to think of this is that for every unit of electrical energy used to power a heat pump, 2.5 to 3.5 units of heat energy are moved. One unit in, roughly 3 units out. For comparison, an oil boiler or furnace may take in one unit of energy to emit 0.8 back as heat.
This reality is what makes heat pumps so much more efficient than standard electrical resistance heating systems, such as plug-in space heaters, electric boilers, electric furnaces, or electric baseboards. Converting a building from primarily electric resistance to primarily heat pump has the potential to result in substantial energy savings with a short payback period.
For other heating systems, such as those boilers, furnaces, or pellet stoves, the cost comparison depends on the relative cost of these fuels compared to electricity. Because each of these different fuels have different cost metrics (dollars per gallon, dollars per kWh, dollars per cord, etc), we must standardize the values to the heat content of the fuel. We use Dollars per Million BTUs of delivered heat. As shown in the graph below, air source and ground source heat pumps produce the lowest cost per million BTUs of any fuel.
How do heat pumps reduce greenhouse gas emissions?
The energy input for heat pumps is electricity, which in Alaska is almost always purchased from the local utility. In communities whose electricity is primarily provided by hydropower, wind or other renewables, no greenhouse gases are created when the heat pump uses the grid’s electricity to operate. In Southeast Alaska and Kodiak, using heat pumps instead of heating oil or biomass will directly reduce your carbon footprint.
Fuel oil #1 and fuel oil #2 both emit around 160 lbs CO2 for each million BTUs of delivered heat or about 22 lbs CO2 per gallon of heating fuel. Additionally, biomass systems also produce CO2 as a result of combustion, however due to varying factors, standardized figures are not available. Air source heat pumps, ground source heat pumps, and electric resistance systems in communities powered by 100% renewable energy produce 0 CO2 per million BTUs.
However, most of the refrigerants used to allow heat pumps to operate are potent greenhouse gases, often 1000 to 4000 times more powerful than CO2. In order for the environmental benefits of heat pumps to be realized, households must ensure that their system does not leak refrigerant, and that installers properly dispose of or reuse any replaced refrigerant. Lower GHG-potential refrigerants are being developed for residential heating systems and are becomming the standard.
How could heat pumps improve my health?
Heat pumps do not burn anything to produce heat. Your building’s indoor air quality will not suffer due to higher levels of particular matter, carbon monoxide, nitrous oxides, sulfurous oxides, or black carbon. In addition, because there is not a flue pipe bringing combustion wastes outdoors, your neighborhood’s outdoor air quality will improve as well. Every year, studies show the significant negative impacts of poor air quality on lifelong health. Most heat pumps include air filtration devices in the indoor air handler.
How do heat pumps help my community?
Heat pumps help communities by reducing carbon emissions, improving local air quality, creating jobs for local contractors, and utilizing local enegy sources, reducing dependence on imported fuel sources.