Efficiency 101
Highlights
- Heats Pumps 101
- Types of Heat Pumps
- Space Heating
- Your Heat Pump & Water
- Water Heating & Other Applicances
Efficient, Clean, Convenient, Healthy
If you are looking to reduce your home or business’ energy bills, localize your energy use, or reduce your environmental impact, heat pumps are one of the best investments you can make. Southeast Alaska communities are leaders in statewide heat pump adoption, and with AHS financial incentives, there really has been no better time to make the switch.
- Heat Pumps 101
- Type of Heat Pumps
- Space Heating
- Your Heat Pump & Winter
- Water Heating & Other Appliances
Heat Pumps 101
Learn about what heat pumps are, how they work, how savings can be achieved, and why heating with heat pumps is better for you, your wallet, and your community.
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.
Types of Heat Pumps
Which kinds of heat pumps are available to consumers, and which ones are most effective in different situations? With air source, ground source, geothermal, geoexchange, seawater, and other versions touted as heat pump options, home and business owners are justifiably confused about what would be best for them.
Air Source
By far the most popular type, these systems transfer heat from the air outside your home to the air inside your home. Heat is gathered from an outdoor unit, such as this Daikin model below, which contains a heat exchanger and a compressor. Inside the home, heat can be distributed using interior units or forced air duct work. Air source heat pumps cost less than ground source heat pumps, but have lower seasonal efficiencies. Most homes will find that air source heat pumps offer lowest life-cycle cost.
- With ductless units, either wall mounted heads, floor mounted units or ceiling cassettes, refrigerant lines run directly from the exterior unit to the interior unit(s). A second heat exchanger in the interior unit allow heat to move from the refrigerant to the indoor air, which is then blown into the room.
- With ducted units, refrigerant lines run from the outdoor unit to a furnace-type heat exchanger. The warmed air is then distributed throughout the building using duct work.
- For buildings without pre-existing duct work, mini ducted systems can be installed on interior heads, which allow heat to be distributed to hard to reach parts of a building.
- Most houses with hot water baseboard are not compatible with air source heat pumps because the temperature of the water produced by heat pumps is much lower than that of boilers. Significant modification of the hydronic distribution system may be required to convert it to a water heat pump system.
Ground Source
These systems (also known as geothermal or geoexchange systems) transfer heat from the ground outside your home to the air in your home. Ground source systems come in multiple types, but each gather heat from the near-surface ground. Using refrigeration cycles, the ground heat is then transferred into your building and distributed using forced air ducting or a hot water radiant heating system. Ground source heat pumps can achieve higher efficiencies than air source heat pumps, but have considerably higher initial installation costs.
- Ground source heat pumps come in three main configurations: open source, closed source, and RX. Each vary based on how heat is brought to the refrigerant.
- Open source ground loops pipe ground water directly into a heat exchanger in your building. Heat is then transferred from the ground water to the refrigerant and is then distributed throughout the building.
- Closed source ground loops bury piping several feet underground. Water, mixed with a nontoxic antifreeze, is then pumped through the piping. Heat from the soil surrounding the piping is transferred to the water solution in the piping, and the water solution is then pumped back into the building and introduced to refrigerant lines in a heat exchanger.
- RX systems bury refrigerant lines directly in the soil, which makes pumped ground water or a pumped antifreeze solution unnecessary. While these systems are more efficient, the upfront costs are significantly higher.
- Heat captured by ground source heat pumps can be distributed throughout a home using either ducted forced air or hot water radiant heating systems.
- In a ducted forced air system, refrigerants release heat into a centralized furnace-type system, which is then distributed using attached duct work.
- In a hot water radiant system, refrigerants release heat into a hot water tank, which is then released by valve to different areas of a building. In each room, in floor radiant heat or hot water baseboards allow heat to be released into the air.
- For retrofits, most houses with hot water baseboard are not compatible with GSHPs because the temperature of the water produced by heat pumps is much lower than that of boilers. Significant modification of the hydronic distribution system may be required to convert it to a water heat pump system.
Seawater Source
These systems transfer heat from seawater to the air or water in a building. Because of high upfront costs, seawater systems are used primarily by large facilities which as the Ted Stevens Marine Research Institute in Juneau or the Alaska Sealife Center in Seward.
Space Heating
Heating your building is the most common use of heat pumps. Because heat pumps transfer heat, not create heat, they are significantly more efficient than traditional electric resistance heat that is used with baseboards or electric boilers. In Juneau, heat pumps are commonly 2.5 to more than 3 times more efficient than traditional electric resistance over a heating season. Compared to heating oil, wood, and electric resistance, heat pumps will provide significant discounts to your heating bills, depending on the cost of fuels. Heat pumps for space heating in homes and other small buildings can be air source or ground source.
Efficiency and Cost
The high efficiency of heat pumps allows for your building to be heated at low cost, compared to electric resistance as well as fuel oil, biomass and propane. For every unit of electrical energy you purchase to power a heat pump, 2 to 3 units of heat energy are delivered into your building, averaged across seasons. When calculated in absolute heat energy terms, air source heat pumps cost 50 to 60% less than fuel oil, propane, wood pellets or electric resistance to provide the same amount of heat. With large enough energy savings, the heat pump can pay for itself.
Distributing Heat
Heat Pumps have four main ways to distribute heat throughout a building: ductless systems, ducted systems, mini ducted systems and hot water systems.
Ductless
- Ductless heat pumps connect the exterior heat collection units with the interior heat distribution units. There can be a single distribution unit in your main living space, or there can be multiple interior distribution units spaced throughout a building.
- Ductless systems are most cost effective when delivering heat to open, main areas of a building. Costs rise quickly when attempting to meet the heating needs of hard to reach rooms. Consider combining a heat pump in the main living space with an electric boiler or electric furnace providing heat to hard to reach rooms.
- Refrigerant lines run between the exterior and interior units, which brings heat from the outdoors into your building.
- Moving heat with ducts create efficiency losses, so ductless units are generally more efficient than ducted units.
- Ductless units usually have the lowest upfront cost of all options.
- Ductless systems only work with air source heat pumps.
Ducted
- Ducted systems distribute heat through a building’s duct work. Using a furnace-like unit, heat from the exterior is released in a central heating unit, and distributed throughout a building with fans.
- Ducted systems experience heating losses as the heating travels through the ducts to the building’s rooms and are less efficient than ductless systems.
- Installing duct work upfront can quickly make a ducted system uneconomical. Ducted systems work best when duct work already exists from a pre-existing heating system or in new construction.
- Because ducting is designed to meet all of a building’s room’s heating demands, there are no substantial increased costs of providing heat to hard to reach rooms.
- Ducted systems can work with air source or ground source heat pumps.
Mini Ducts
Mini ducts, or short-ducted mini split systems, use small indoor low-pressure fan coils with short ducts to serve multiple small rooms. These types of systems can be an alternative to multi-head systems, and are particularly useful in situations where multiple rooms, removed from the main open space of a home, need to be served.
A common issue homeowners run into when considering a whole-house heat pump retrofit is providing code-compliant heating to backrooms such as bedroom. Miniducts are a possible solution to this. An alternative is a hybrid heating system which uses a heat pump in the main living space combined with a electrified legacy system (boiler or furnace) which solely heats the back rooms. Homeowners considering a whole-house retrofit should weigh the financial costs of these two options.
Hot Water
- Ground source heat pumps can provide heat to water, which can then heat your building using hot water baseboards or in floor radiant heating.
- Because ground source heat pumps are more efficient than air source heat pumps, hot water systems which can only be used with ground source heat pumps are generally more efficient.
- However, higher up-front costs for both new construction and retrofits make hot water systems generally less economical than ductless systems.
- Most houses with hot water baseboard are not compatible with GSHPs or air to water heat pumps because the temperature of the water produced by heat pumps is much lower than that of boilers. Significant modification of the hydronic distribution system may be required to convert it to a water heat pump system.
- One significant advantage of GSHPs and AWHPs is that they are able to perform double duty, heating the space as well as heating domestic hot water. ASHPs are not capable of that.
Your Heat Pump & Winter
During our usual snowy and humid winter months, heat pump owners should know the best tips and tricks to make sure their home’s heating system is a top performer.
FYI…the two images below are NOT what you want your heat pump compressor to ever look like!
1. Make sure your external unit doesn’t get buried or confined by snow.
Your outdoor compressor needs lots of good airflow. This does not just mean behind and on the sides, but also in front. You want the compressor to have access to warmer outdoor air and it needs to be able to move the colder air it produces away as easily as possible. Objects up to ten feet in front of the compressor can cause cold air back flow which will reduce the ability of the unit to extract heat from the ambient air. Check for clearance after any big changes in snowfall and how it accumulates (plowing, shoveling, drifting, roof avalanches). Ideally your heat pump compressor is protected by a small roof of some type. Many ideas are available with a quick web search.
2. Watch for ice under your external unit.
The compressor naturally drips condensate. In winter this can freeze and make a walking hazard depending on the location of the external unit. This ice under the unit is normal and during extended cold spells, it can build up into a mini glacier. This refrozen condensate ice should not present any issues. If it seems to be creeping up along the back or sides of your outdoor unit, it is best to leave it alone and allow the drain pan heater and defrost cycles to keep it in check. In the rarest of situation, ice buildup can cause ground shifting and actually move the compressor. If you see or suspect that this may be occurring, contact your installer as soon as possible.
3. Watch for ice ON your external unit.
Ice build (not frost) up on the compressor – along the sides, back, and climbing up from the base – is often indicative of a performance issue, such a slow refrigerant leak or an iced over defrost thermostat. If you notice that external unit is icing up (lots of heavy frost) contact your installer immediately or contact one of the contractors here. Waiting too long for a repair can be detrimental to the lifespan of the system. One temporary trick to de-ice your compressor is to run the heat pump in AC mode for 15 – 20 minutes. We’ve also heard that gently pouring very hot water into the base pan, while the fan is not actively spinning, can help to free up a frozen defrost thermostat. While this will pump cool air into your home, it will send heat to the compressor and clear it of ice fairly quickly. Still, call a contractor for service – asap.
4. Increase the fan speed for greater heat distribution.
Cold outdoor temperatures often require a slightly different approach to using your heat pump. Turning up the temperature a couple of degrees with your remote will help of course. But, so will increasing the fan speed. By upping the fan speed, the heat pump will not only move more air across the indoor heat exchanger, it will push the warmed air further into your home. The AUTO fan setting is best for most occasions, but at night, it can help to run the fan more briskly. The louder fan will do its work while you sleep and you should wake to a warm home. Turn the unit back to AUTO once you are up and about. If you have been lowering the temperature at night, leave it up at your daytime setting.
5. Check and clean the air filter on the interior unit…often.
Winter is when your system needs its efficiency the most, so be sure it has good airflow. Check the filter at least every two weeks and clean when necessary. The environment of the indoor unit can greatly influence the frequency of needed cleanings. Heat pumps in shops or homes with furry pets, for example, may need their filters cleaned of sawdust or hair much more often.
6. Watch your pipes!
Especially when you’re enjoying your heat pump in its first winter, check your water pipes when it gets really cold to make sure they don’t start to freeze. Eliminating a boiler, or reducing its use, eliminates waste heat in the boiler room, garage, or other space, often where exposed water pipes tend to live. Keep an eye on them when it gets cold, and take measures to warm them up if necessary (heat tape, extra sources of heat, leave a very tiny trickle of water running).
7. Watch your hydronic baseboards!
Just like the situation above, if you still have a boiler for backup heat, make sure that the spaces your baseboard piping are in don’t freeze (baseboards often run around the cold perimeters of houses, so they are particularly vulnerable). Run the system a little, perhaps, just to avoid any risks.
8. Check your system balance and thermostat harmony.
If you have two different heating systems, make sure that your thermostats are in locations and at settings that will work together, in the most efficient way possible. If you have a heat pump in your main living space and a different kind of heat in your other rooms, you want your heat pump to turn on first and produce as much efficient heat as it can before the other systems turn on (especially in homes with forced air, where the backup system is otherwise heating the same space as the heat pump). Make sure that other system does turn on, though, or back rooms may get too cold. If the thermostat for the back bedrooms is in the same room as the heat pump, it will never click on because it’s always nice and warm. Consider moving this thermostat to a more isolated location. An electrician can do this for around $200. You’ll recoup this savings in no time by allowing your heat pump to take on more of the home’s heating load.
9. Check your thermostat setbacks.
You don’t want a ton of variation (“set it and forget it”), but our own experiments show that some amount of nighttime setback is beneficial in creating even more cost savings. Don’t overdo it though. Especially during cold winter periods! The heat pump will take longer to warm your home than your old oil system did. It is best to keep the temperature as steady as you can. A couple of degrees cooler at night is the most you should set the heat pump back. When it’s really cold out you may not want to set the evening temperature back at all.
Water Heating & Other Appliances
Heat pump water heaters (HPWH) and heat pump clothes dryers are two examples of how the energy efficiency of heat pumps can make electricity-hungry home appliances efficient and easy on your wallet.
Heat Pump Water Heaters
Energy Star estimates that a family of 4 could save $3,750 with a heat pump water heater over the lifetime of the unit. HPWH’s efficiencies and cost savings depend greatly on where the unit is placed. Alaska Heat Smart continues to study these systems and their utilization. Please check back regularly for updated guidance. HPWHs will cool down their surrounding space, so careful consideration must be given to the potential for freezing pipes in some circumstances.
Learn more from Energy Star’s Heat Pump Water Heater page.
Heat Pump Clothes Dryers
Clothes dryer can use heat pumps to reduce energy by at least 30% compared to standard dryers, according to Energy Star. In addition, these dryers do not require ventilation, are easy to install, and are generally easier on clothes.
Learn more from Energy Star’s Heat Pump Clothes Dryer page.
Invoice Example
All of the information in red is required to be on both heat pump installation and electrical invoices (heat pump model number does not need to be included on an electrical invoice). Right click to enlarge the image.
This project has been funded wholly or in part by the United States Environmental Protection Agency under assistance agreement #84101201 to Southeast Conference (SEC). The contents of this document do not necessarily reflect the views and policies of the Environmental Protection Agency, nor does the EPA endorse trade names or recommend the use of commercial products mentioned in this document.