Greening Homes With Heat Pumps

As homeowners seek to be greener and governments incentivize alternatives to fossil fuels, heat pumps are growing in popularity for both new construction and home updates. To explain the different uses for heat pumps around the home and the benefits, Jean-Pierre Clejan, the technology executive for GreenLogic Energy, delivered a presentation to AIA Peconic members last week at a near-net-zero Wainscott home.

Despite the name, heat pumps both heat and cool homes. The technology is also used for domestic hot water, heated swimming pools and clothes dryers. Some heat pumps use air to move heat around — which has limitations in extreme cold or extreme heat — while geothermal heat pumps use the consistent temperature of the earth under ground to operate effectively and efficiently regardless of the air temperature.

The first heat pump was built in 1856, but it wasn’t until recent years that heat pumps caught on a cost-effective way to condition homes. In 2022, air-source heat pump sales overtook gas furnace sales in the United States, according to the International Energy Agency. As New York State seeks to electrify homes and use more clean energy that doesn’t produce greenhouse gases, the prevalence of heat pumps will only continue to grow.

Clejan walked the members of AIA Peconic — the East End’s chapter of the American Institute of Architects — through how heat pumps work, their different applications in single-family homes and limitations to take into consideration.

How Air-Source Heat Pumps Work

“A heat pump moves heat from one place to another,” Clejan said.

He explained that an air-source heat pump uses a compressor to compress a refrigerant gas, and the gas gets hot in the process. As the compressed gas expands again, it discharges heat.

“Your refrigerator kind of works that way,” he said. “You’re chilling, you’re pulling the heat out of the cavity of the refrigerator, getting cooler. Where does that heat go? It goes into the coils in the back of the refrigerator.”

In the summer, the heat pump moves heat from inside the house to the outdoors. In the winter, it works in reverse, heating the indoor air and chilling the outdoor air.

“All this requires is some electricity and a hot side and a cold side,” Clejan said.

Heat pumps use less electricity to heat homes than electric resistance heaters, such as electric baseboards, which are expensive to operate. An electric resistance element, which is the same technology used in toasters, is 100 percent efficient, Clejan said, but “it has no mechanical advantage.”

A heat pump has anywhere from a 3-to-1 advantage, when using an air-source heat pump, to a 6-to-1 advantage, when using a geothermal heat pump, he said. “The same electricity creates a lot more heat.”

Limitations of Air-Source Heat Pumps

While air-source heat pumps work very efficiently in both cool and warm temperatures, when the outdoor temperature falls to extreme cold or rises to extreme heat, air-source heat pumps run into trouble.

“At both ends of the spectrum, they work very hard,” Clejan said. “When it’s really hot out, you’re trying to push the heat into 100-degree air. That’s not very efficient. On the cold end of the spectrum, you’re trying to pull the heat out of 20-degree-Fahrenheit air. So it’s inefficient at both ends of the spectrum.”

An air-source heat pump will continue to work in extreme heat, though with high electrical demand. In extreme cold, it won’t heat a home adequately. For homes that don’t use a backup heating appliance, geothermal, or ground-source, heat pumps are the way to go if the installation is permitted and feasible.

“If you’re going to be warm on the coldest days of the year, either it has to be way oversized, or you’re going to need an electric resistance backup or flame-based backup,” Clejan said. “A good geo shouldn’t need a backup to give you all the heat it needs.”

Ground-Source Heat Pumps

Ground-source heat pumps are also known as water-source heat pumps or geothermal heat pumps. They heat and cool homes using water that is pumped down into the earth, where the below-ground temperature on Long Island is 53 degrees all year, then pumped back up into the home.

“If you have to outdo the financial performance of natural gas and central air, geothermal is the only thing that will do that,” Clejan said. “If you’re competing against propane or fuel oil, the air-source heat pumps will give you a better financial performance [than propane or fuel oil].”

Installing a geothermal loop requires drilling deep, typically 250 feet. It can be challenging or impossible to get the drilling equipment where it needs to be on a property that is already developed. It’s easiest to accomplish with new construction, though Clejan noted that on Shelter Island drilling a geothermal loop is prohibited. On the South Fork, it’s permitted, but there are setback requirements.

Open-loop heat pumps either dump the used water or put it into a dispersal well so it returns to the aquifer, which creates water conservation concerns. In fact, the Suffolk County Water Authority decided in 2020 that it will no longer approve applications for open-loop heat pumps.

Closed-loop heat pumps reuse the same water — a solution of water and glycol — indefinitely, so water conservation is no concern.

Heat Pump Water Heaters

Heat pump water heaters use the air in a basement.

“It inhales ambient air, it chills the ambient air, pulls the humidity out of it, and exhausts colder air,” Clejan said. The heat goes into the water tank, and the basement is cooled and dehumidified in the process, too.

In the dead of winter, the heat pump water heater could pull the basement temperature down to 50 degrees, he said, although he encouraged weighing that against the benefits of dehumidifying the basement. “It could become uncomfortably cold, but it will be nicely dry,” he said.

For the heat pump water heater to work in a year-round home, adequate indoor space is necessary.

“You do need to let the system breathe,” Clejan said.

For maximum efficiency, the basement should be 1,200 square feet, and the mechanical room should be at least 400 square feet with louvered doors.

“With a heat pump water heater, you can actually make hot water using LIPA power at LIPA rates for less than using propane or oil to make the same hot water,” Clejan said. “Gas would be a little cheaper than LIPA power, but remember that the gas hookup costs $30 a month. So if this was your only gas application, it probably wouldn’t make sense to bring in the natural gas for that purpose.”

He added that an electric resistance hot water heater uses an “absurd” amount of power and would be prohibitively expensive at LIPA rates. “An electric heat pump is three or four times as efficient as that,” he noted.

He also pointed out the benefits of switching from flame-based hot water solutions: “By switching away from that flame, we’ve reduced carbon emissions and increased the safety of the house. We don’t have to worry about puff backs, carbon monoxide poisoning — that kind of thing.”

Heat Pump Pool Heaters

Clejan said the most dramatic application of air-source heat pumps is seasonal pool heaters. He shared a price model that compared heating a pool to 80 degrees from May 1 to October 1 using propane and using a heat pump. He used the going LIPA rate for the cost of electricity, and $3 as the average price of propane. He found that operating the propane pool heater would cost $4,500 for the season while operating the heat pump would cost only $1,260.

He added that the heat pump does not need to be turned off at times to save money. “You set it and forget it, and you get this amazing result,” he said.

Propane prices on Long Island have averaged more than $4 per gallon since 2022 — $4.23 per gallon as of September, according to the New York State Energy Research and Development Authority — so the savings with a heat pump is even more pronounced.

Clejan noted that a heat pump pool heater will be inefficient and ineffective when the air temperature is below 50 degrees, but otherwise is “super, super efficient.”

“Efficiency really starts at 60 and up, but I don’t know how many people are jumping in their pools when it’s 50 [degrees] Fahrenheit,” he said.

A heat pump can also be used to heat a summer hot tub, but not a year-round hot tub, he added.

Takeaways

For further savings opportunities, homeowners can install solar panels.

“You can make the electricity to do this,” Clejan said. “You can never make the propane to do the same thing.”

He also highlighted the advancements that have been made in heat pump designs.

Older systems were sized one of two ways: based on the load needed for summer demand or the load needed for winter demand.

Clejan explained that today’s geothermal heat pumps have two stages, with 60 percent of the heat pump’s power in stage one and the other 40 percent in stage two. All cooling is done on the 60 percent side. When heating, only stage one is needed until temperature dips to about 40 degrees. Then stage two kicks on as needed.

With PSEG rebates and state and federal tax credits, the cost of installing a geothermal heat pump system can be comparable to installing a conventional HVAC system, according to Clejan.