The best current technology for heating and cooling homes and buildings is the heat pump, which comes in air source and ground source varieties
Here’s what a typical air source heat pump with mini-split installation looks like. It comprises one or more outdoor pump units, and one or more indoor mini-split units, connected with small flexible pipes that carry refrigerant. Town Hall uses this technology in the new wing. You can see the indoor mini-split unit in Conference Room 9.
How do these systems work, and why are they good solutions for heating and cooling?
Heat pumps get most of their energy from the air or ground outside. Refrigeration technology takes advantage of how heat is absorbed when a gas turns to liquid, and how it’s released when a liquid turns back to gas. Even when it’s cold outside, there is still energy in the air, and modern heat pumps can extract energy down to 10 or even 20 degrees below zero, and bring it inside. For those few super-cold days that occasionally happen, supplemental heat is used, such as conventional electric heat. In hot summer weather, the cycle runs in reverse, providing air conditioning nearly twice as efficiently as other systems. The use of energy from the grid is only ⅓ to ¼ of the energy used in the system, because most of the energy comes for free from the air or the ground outside.
We’ve been talking about air source heat pumps. There are other versions:
- Ground source heat pumps take advantage of the steady temperatures below the frost line. Though they are even more efficient than air source heat pumps, the higher capital cost of ground source systems has become harder to overcome as air source technology improves.
- Heat pump technology can also be used for water heating, which is typically done with an all-indoor system in the basement.
- Heat pump heating and cooling systems can use small flexible tubes to transport the refrigerant, eliminating the need to add expensive ductwork.
- For retrofits, systems can use existing heating or AC ducts, saving on installation costs, and allowing for a single central heating and cooling unit inside.
So what’s the financial story on air source heat pumps?
Heat pump operating costs are lower than those for any other available option because of the free energy heat pumps get from the local environment. With the incentives that are available to cushion the installation costs, heat pump costs are similar to those for other heating and AC solutions. Thus, they save money as soon as they are turned on. As an upgrade from oil, coal, gas, or propane, heat pumps begin to save money — sometimes called the “payback” point — within a few years. As an upgrade from natural gas, at current gas and electricity prices, payback can take as long as 30 years. The payback period is shorter if the alternative is an expensive repair to an existing heating or AC system.
Here’s the heating part of the operating cost comparison, from a great site called “Efficiency Maine.” You can type in expected prices for various fuels and the site then shows you the expected operating cost. At typical prices, heat pumps are by far the least-expensive option.
Here’s the cooling part of the cost comparison. The key measurement is called the SEER ratio. As this efficiency rating goes up, costs go down. Heat pump systems operate at very high efficiency, with SEER ratings of 20–30 so unless you have a very new AC system, cooling with a heat pump will cost less.
Incentives for heat pump systems are available as rebates from both the state’s Clean Energy Center and from Mass Save. And a remarkable state loan program offers so-called HEAT loans, which are interest-free loans for terms as long as seven years. These can help make some upgrades cash-flow positive fairly quickly. There is also currently a 30% federal tax credit, but we don’t yet know yet whether this will extend into 2017.
You can see our recommendations here, but to summarize: It is especially urgent to prevent new natural gas infrastructure that will lock in fossil fuel use for decades. Clearly, heat pumps are part of the solution for reducing fossil fuel use in meeting Acton’s heating and cooling needs. We recommend that the Board of Selectmen affirm these goals, and via the Town Manager, direct staff and boards to educate homeowners, developers of single and multi-family homes, real estate agents, and the public on heat pump technology, and how and why to adopt it. We recommend that research be done on additional ways for the Town to discourage new natural gas infrastructure. We also recommend that the Selectmen consider tasking an existing or new town entity with creating an overall carbon reduction plan for the Town. And finally, we commend the work the Town has done already, including creation of the Acton Power Choice plan and working with the gas company to coordinate upgrades to their leaky gas infrastructure.
Thank you all for your time and your thoughtfulness on these issues. We look forward to the next part of this dialogue.
(Read Part 1 here: mostly about Climate Change)