Most American homes are heated with fossil fuels, the majority with natural gas.
But electric heat pumps can be a great energy-efficient alternative that lowers carbon emissions and fossil fuel use.
By using electricity and a compressor, a heat pump can both keep you warm in the winter and cool you off in the summer.
“It uses electricity to drive a compressor. But now, it takes heat from the outside and ‘bumps it’ into your inside space. And in doing that, it is far more efficient on most days than baseboard heating,” Columbia University professor Vijay Modi says.
What are heat pumps?
“Heat pumps are very similar to air conditioners. You come home on a hot day. You turn it on. It cools down your room. But even after the room is cool, the outside heat wants to keep coming in. And what an air conditioner does is, using electricity and a compressor, keeps your room cool by taking heat from inside the room and dumping it outside. And that way, it maintains a steady core temperature inside. A heat pump can do both: Keep you cool in the summer and keep you warm in the winter using a compressor.
On the difference in cost
“There are two issues of cost. One is the first cost and then the recurrent cost. Let's talk about the first cost. Most homes in the U.S. have a central-forced air heating system. Many already have a central air conditioning tied into that forced air system. If you have that then the next time you replace your AC, you'll just replace it with a heat pump and it would only cost you a couple of thousand dollars more. If you don't have an existing center air, it may cost you six, seven, eight thousand depending on the size of the home. But the good thing is it will do both cooling and heating for you.”
On operating cost
“So in terms of operating cost, let's take a typical cold a day in the Northeast. Let's say it's 30 to 40 degrees Fahrenheit. If you used heating oil, it will take you let's say two gallons a day to heat your home at $3 a gallon. That's about six bucks. If you had one of these heat pumps that I'm talking about, you use about 20 units of electricity to do the same job and that would cost you $3 that day, about half of what you paid for oil. So first of all, if you are using fuel oil or propane on most days, you would cut your fuel bill so to speak by half. But more than that, that fuel oil would have put out about 50 pounds of carbon dioxide in the air.”
“I'm in New York, our grid is clean and it's going to get cleaner, but even with the current grid, I would put out only half the emissions into the air of CO2. So it's kind of a win-win. It's both cheaper to operate and it puts out half the emissions today. Of course, we in New York have just passed a very aggressive law, the Climate Leadership and Community Protection Act, that will drive down those heat pump emissions even lower. Where as, if you continue to use some of the fossil fuels, those emissions won't change.
On whether more homes will start switching to heat pumps
“The dominant number of homes in the U.S. are still heated by gas, propane or oil. And then when they're heated by electricity, they're frequently baseboard. So yes, we do need a transition and we had to make that transition very cost effective. One way to think about it is on a very cold day, which only happens let's say at 10 or 15 times in a year, you may need a much bigger heat pump and then it starts to be not good on the customer’s pocketbook. But if you already have a gas or propane or oil fired forced air system, you could actually add a heat pump to that system so that now you have what is called a dual source system, so that on most days you would use electric, except for those very cold days you would continue to use gas.
“What's interesting is that if you took this hybrid approach on those very cold days, yes, you would use gas. But the total amount of gas you would use would actually come down by 90%. And other thing is on those very cold days if everyone started to use a heat pump, it could stress the electric grid. And this approach allows us to not have to make huge investments in the electric grid right away and continue to use both electric and gas and yet reduce our emissions dramatically.”
On how big of an impact heat pumps could make on our carbon footprint if more Americans switched over
“First of all, very significant, but especially the ideas that I have studied in the Northeast, we would have a very big impact. And the reason is that currently the building sector is one of the largest emitting sources of emissions. And in the building sector, the dominant emissions are from heating, not from using your TV or lighting. And so if we could take such approaches where we both clean the grid and deploy these efficient heat pumps then the emissions from heating could be reduced by as much as 90% by using this new approach.”
This segment aired on August 29, 2019.