Heat Pumps

Are Mini-Splits the Same Thing as “Heat Pumps?” and Other Questions about Electric Heating and Cooling

Introduction

Cold climate heat pumps were developed in the 1980’s and 1990’s to heat homes and other buildings with electricity. They are becoming so popular that from 2022 to 2024 more heat pumps were sold than gas furnaces. That trend is only increasing. Today, about 10% of all heat provided to buildings worldwide comes from heat pumps. Still, most of us have questions.

Can you really take heat out of ambient air at minus 10 or 20 degrees Fahrenheit and heat your house with it? Are heat pumps something you should consider when replacing your furnace or boiler? For new construction? Or for more efficient air conditioning? So, what are all the pros and cons of choosing a heat pump?

Answers, anyone?

Air-Source Heat Pump

Air to Air Heat Pump - Outside / Head, Air Handler, Indoor Heat Exchanger - Inside

Ground-Source Heat Pump

Geothermal Heat Pump

What is a heat pump? What are the different kinds of heat pumps?

In the most simple terms, a heat pump is a device that captures heat from one place and transfers it to another using electricity to run a compressor.

In this context, we discuss the heat pumps that heat and cool homes and businesses. For example, during the winter, air-source heat pumps can capture heat from the outside air (even in very cold temperatures) and transfer it inside to warm a home. During the summer, the heat pump works in reverse to capture heat from inside the house and transfer it outside, effectively cooling the house.

There are also ground-source heat pumps (also known as geothermal heat pumps), which require a connection to hundreds of feet of underground pipes or coils where the temperature is constantly in the mid-50s. Water circulates through those pipes during the winter and the heat pump captures heat from that circulating water and transfers it into the house in order to warm the house. During the summer, heat is transferred back into the water in the pipes, effectively cooling the interior. Often, ground-source heat pumps will transfer heat from the pipes into a hot water tank, which then provides domestic hot water.

Air-source heat pumps and ground-source heat pumps are the two most common types of heat pumps used for residential heating and cooling. Both can be designed to work by forcing hot or cold air through pre-existing ductwork just like a typical duct heating system. Or, they can rely on refrigerant lines that carry hot or cold refrigerant to one or more indoor air heat exchangers called mini-splits. One outside heat pump can be connected to several inside mini-splits to distribute the heat or cool throughout the house.

There are also heat pump water heaters, which capture heat from surrounding air and transfer it into a water tank for domestic hot water uses. Heat pump clothes dryers use a similar technology to dehumidify and dry clothes. But here we’re focusing on the heat pumps that heat our homes during the winter and keep them cool during the summer.

How does a heat pump operate?

A heat pump operates much like a refrigerator or air conditioner. That is why they can operate to deliver heat in the winter and air conditioning in the summer by reversing the flow. The working fluid in the device undergoes changes from a gas to a liquid and back again in a cycle while absorbing and releasing heat. A more detailed diagram is shown below. The first heat pump was invented and built in the 1850’s. The technology has undergone lots of improvements since then.

Can air-source heat pumps effectively heat homes in New York winters? 

Yes. 

Ground-source heat pumps have been used for decades in cold climates like New York. Up until the last 10 years or so, air-source heat pumps were primarily used for air conditioning in the summer, and perhaps for a little heating in the “shoulder” months, when temperatures were still in the 40s. But over the last few years, there have been huge strides in the technology used to capture heat from very cold temperatures with cold climate air-source heat pumps. Now many models can still operate efficiently down to -5º or -10º F or even lower. 

On December 23rd, 2024, when temperatures in Warwick dropped a few degrees below zero, Sustainable Warwick surveyed several heat pumps users. We asked survey respondents how comfortable their home was that day, and we received no messages that anyone’s system had failed. A few people mentioned they ran an auxiliary heat source, such as a wood stove or a legacy boiler, or put on an extra sweater that day. 

Michael Helme said, “Our home was comfortable enough the day temps dropped below zero. We could have turned on our old boiler, which is there as a backup, but it wasn’t necessary. Having said that, to us it makes sense to wear long johns and sweaters on the coldest winter days, and we naturally gravitate toward rooms that stay the warmest. If we wanted to run around all winter in t-shirts and shorts, then we would have needed more heat. But our first step would have been turning up the thermostat on the heat pumps, and if need be we would have turned on the propane boiler, which hasn’t run at all for a couple years now.” 

 

A survey respondent from Putnam County sent this screenshot of an Instagram post:

Who should consider heat pumps?

Anyone who wants to

  • replace an existing heating system

  • find more efficient ways to heat without “deliverable fuels” (such as propane or fuel oil) or wants to replace fossil gas, or has standard electric heat.

  • add air conditioning to an existing house

  • significantly reduce their carbon footprint

  • heat and cool a new house addition or has some other area that needs better heating and cooling

Why are cold climate heat pumps such an effective technology for heating and cooling homes?

Cold climate heat pumps, also called "cold weather heat pumps," are considered an excellent technology for homes in New York because they can provide very efficient heating, even in temperatures well below 0º F, while offering significant energy and dollar savings. The carbon dioxide emissions and other kinds of interior and exterior air pollution fuels are much lower in comparison to typical gas furnaces and oil burners. While heat pumps run on electricity, they can give you 2½ to 5 times the usable heat compared with typical electric heating. When paired with their cooling capabilities in warmer months, it makes them a versatile year-round option while minimizing environmental impacts. Advancements in design, such as improved refrigerants, larger heat exchangers, and other technology developments, allow them to operate effectively in any climate. 

What kind of heat pump should I install in my house?

Two categories of heat pumps are defined by where they get the heat; they are air-source heat pumps, where the heat is extracted from outside ambient air, and ground-source heat pumps, where heat is extracted from earth or water.

Ground-based systems generally last longer, but are more expensive and complicated, and more often found in new construction. Air-based systems have a shorter lifetime, but are cheaper and easier to install and more often found in retrofits, replacing existing oil, gas or standard electric heating systems.

The technology is rapidly expanding. There are now heat-pump hot water heaters, and heat pumps that transfer heat from air to water, which can be coupled to existing liquid radiator and radiant floor systems, retrofits through windows, and more.

Existing homes with and without existing ductwork can be renovated to work with heat pumps, and heat pumps should be the first consideration replacing existing fossil fuel heating systems or when contemplating new construction. 

What other steps should you take if you are considering a heat pump?

Both NYSERDA (the New York State Energy Research and Development Authority) and Consumer Reports recommend evaluating the heat loss of your house and taking steps to improve house energy efficiency. This is a wise move to save energy and money whenever you are changing any heating system. If needed, insulating surfaces and sealing air leaks will allow you to install a smaller heating system that will cost you less. Also, the less energy loss your house has, the lower the energy consumption will be for heating and cooling it. And an efficient house will be more comfortable than a leaky one. Generally, you will need an electrical box with 200 amp service. There is currently a $600 incentive to help with this if needed.

What does it cost to buy and install cold climate heat pumps?

The cost will depend on a number of factors, including the size of your house, the heat loss of your house and the size of the heat pump needed, and how to best distribute the heat throughout your house. Generally, heat pumps might cost somewhat more than replacement furnaces or boilers, but there are associated tax credits and rebates that reduce the cost, and the ongoing operating expenses tend to be lower (you never have to buy oil, gas or propane again, a significant savings).

Sizing a heat pump system for your house requires a trained heat pump technician to do the calculations, following industry standards. Locating the heat pump outdoors and the indoor units to distribute heat also requires a trained technician. Each house is unique. SW recommends you get a few quotes from experienced companies with quality equipment that have a record of successful installations, just as you would for any HVAC system. Also, remember to consider the warranties along with the maintenance and reliability record of the company.

What were the results of the Sustainable Warwick Survey on Heat Pumps?

Why did you decide to get heat pumps?

More than half the respondents were motivated to get off fossil fuels or improve their energy efficiency. Several appreciated the opportunity to get air conditioning at the same time. One respondent said it was a huge improvement when they replaced electric resistance baseboards.

What do you like about your heat pumps?

Many respondents said their heat pumps were easy to operate, and they liked the extra benefit of having air conditioning.  Some specifically mentioned not using fossil fuels or needing refills, as well as the advantages of not burning fuels inside their home; a few owners noted being able to run their heat pumps with electricity generated by their own solar PV system. Others noted they had improved home comfort, especially with separate zones for each unit. Others liked the quiet operation and general efficiency. 

What do you dislike about your heat pumps?

A couple owners said the mini-splits on the wall were unsightly. One person said they are more drafty than baseboard heat, another commented on a slight draftiness when the split units circulate air to sense the temperature, and another noted a chilly draft when the outdoor unit goes into defrost mode. One person ended up with a completely unheated basement, because of poor planning when the heat pumps were installed. Another thought going from room to room to adjust each unit was cumbersome. 

Are heat pumps expensive? 

The general consensus was that installing heat pumps was a big expense, but any heating system is expensive, especially for retrofitting a home. All the same, rebates helped offset the cost , as did financing from state programs. Moreover, heat pumps have the advantages of lower operating and maintenance costs, plus in most cases they provide air conditioning. For new buildings, heat pumps are much more affordable. When coupled with community solar and especially a home photo-voltaic solar system, the operating costs of heat pumps drop even more. 

Is your home energy efficient (does it have good insulation)?  How has your electricity bill been affected by heat pumps? Do you own a solar PV system or are you signed up for community solar?

Most of the homes were well insulated and a couple of the homes even claimed to be passive solar homes. Four of the respondents specified they have solar panels, while two others indicated having community solar. One of the homes had “fairly good insulation” while another reported bad insulation.

What advice would you give to homeowners who are considering installing heat pumps?

  • Definitely worth it to avoid fossil fuels, especially if you also have solar panels.

  • Get quotes from 3 or more contractors, and listen to their ideas about the best way to install and use heat pumps in your home.

  • Learn what the advice “set it and forget it” means, and why it’s good advice for heat pump owners. 

  • Sign up for community solar. Then follow the AWE steps: Assess your home's insulation and air sealing; Weatherize to the extent practical; then, Electrify it with heat pumps. PV solar should be the last step you take.

  • While they will work anywhere, a well insulated, well sealed house is necessary to get the most comfort and efficiency from heat pumps.  

  • Most heat pumps are air-to-air heat pumps, but there are also air-to-water heat pumps to retrofit in homes with baseboard and radiant floor heating; this may be a good solution for homes that don’t have pre-existing ductwork.

  • Go to it.

Follow Up question: How comfortable was your home when Warwick got to -5 F?

Everyone who replied said they remained comfortable or very comfortable on the coldest days in Warwick this year. Some of the respondents mentioned also using a second heat source, such as a wood stove or prior heating system that had not been removed. 

Could you summarize the main advantages of Heat Pumps?

  • Can be run off of clean energy sources (solar, wind, hydro, geothermal, etc.)

  • Both heat and cool a house

  • Run fairly constantly at a low output level

  • Work down to very low temperatures (-10º to -15º F) (temps valid for cold-climate heat pumps)

  • Reduce indoor air pollution from combustion sources (nitrogen oxides, carbon monoxide, sulfur dioxides)

  • Offer improved safety from fires and explosions

  • Are relatively easy to retrofit for both ducted and non-ducted houses

  • Are relatively “efficient,” saving energy and money over time

  • Significantly reduce carbon footprint and climate pollution which improves as the grid becomes greener

  • Are eligible for tax incentives and rebates available (Federal and state)

  • Reduce outdoor pollution from combustion sources

  • Can be easily added for specific problem areas (such as a new addition, cold areas, and hot areas)

  • Provide a major step towards an all-electric, pollution-free house (with electricity from renewable sources)

Please let us know if you have other questions about heat pumps. We’ll be happy to answer your questions and update this web page.

CleanEnergy@sustainablewarwick.org