Buildings

Worldwide, we emit about 3.6 gigatons of CO₂ each year by burning fossil fuels and biomass inside our homes and businesses.¹ We emit another 5 gigatons each year generating electricity that our buildings use. The 17.5% of global emissions (8.65 gigatons) shown on the pie chart comes from combustion in buildings together with electricity used by buildings. We can drive the emissions from electricity to zero by cleaning up electricity.

The good news is that we know how to stop. Electrifying buildings is simpler technologically than electrifying transportation or industry. Our buildings sit in one place, connected to the electric grid, all the time. So, to heat or cool indoor air, make hot water, and cook food, we don’t need to store energy and carry it around as we do for electric cars. And we don’t need to produce the super-high temperatures required for making things like steel and cement. We can do the jobs we need to do in our buildings with two, mature technologies: heat pumps and induction cooktops. And we can do them while saving an enormous amount of energy (and, in many cases, money), making our buildings safer and more comfortable, and giving ourselves healthier air to breathe.

The bad news is that to deploy these technologies at the speed and scale we need, we have to overcome a lot of social, political, and financial obstacles. We’ll discuss these, and how to overcome them, in a moment. First, we need to understand heat pumps and induction stoves.

Heat Pumps

A really efficient fossil gas-burning furnace can be 95% efficient. That means that it turns 95% of the energy stored in the methane it burns into usable heat. An electric heat pump can be 400% efficient. How is that possible?  (What does it even mean?)  If you ask a physicist, and you catch them with their guard down, they’ll tell you: it’s basically magic.

A heat pump doesn’t turn electricity into heat, in the way that a toaster does. Instead, it uses electricity to move heat around, from one place to another. It works the same way a refrigerator does. If you feel the back of your fridge, you’ll find it’s hot. That’s because coils full of fluid have been pulling heat out of the cold air inside your fridge, and you’re feeling them release that heat into the air behind your fridge, making your warm kitchen even warmer. An air-conditioner does the same thing, pulling heat out of your indoor air, and pumping it into the hot outdoor air. That’s exactly what an air-source heat pump does in summer, when it functions as an air conditioner. But a heat-pump can also run in the opposite direction: in winter, it can pull heat out of the air outdoors (even if that air is already really cold) and release it into your home to warm the indoor air. It can be 400% efficient, because one unit of electrical energy is enough to move four units of heat energy from one place to another. 

⇒ Look at this simple, animated explainer to get a better sense of how heat pumps work.

Or, just look at this basically-accurate explainer by climate artist Nicole Kelner:

Ground-source heat pump systems are sometimes called “geothermal heating” because they pull heat out of the earth, instead of the air. This name can be confusing though, because “geothermal energy” also refers to a very different technology for producing electricity using the high-temperature heat found far beneath the earth’s surface, as we discuss in our page on cleaning up electricity. To avoid confusion, we’ll save the term “geothermal” for geothermal electricity production. A ground-source heat pump works in the same way that an air-source heat pump does, but instead of coils full of fluid transferring heat to or from the air, coils full of fluid transfer heat to or from the ground, which stays a pretty consistent 55° F once you get a few feet underground. Less energy is needed to pump heat into 55° earth than into hot summer air; and less energy is needed to pump heat out of 55° earth than out of the cold winter air; so ground-source heat pumps are even more efficient than air-source ones. But they usually cost more up-front to install, because you have to dig deep holes in the ground for the fluid to loop through.

⇒ To learn how one smart start-up is working to make ground-source heat pumps affordable, listen to this podcast interview with Kathy Hunan, founder of Dandelion Energy.

Both air-source and ground-source heat pumps can heat and cool commercial buildings and multi-family apartments as well as single-family homes. Because they don’t burn anything, there’s no risk of carbon monoxide poisoning or explosions. And because they continuously adjust the intensity they run at to keep a room at the desired temperature (rather than just switching between on and off like a conventional furnace), they’re much more comfortable. Living in a home with a heat pump is like driving an EV: it’s not just environmentally healthier; it’s a better experience.

⇒ Check out this memo describing five heat pump-powered buildings in New York City, including a 44 story mixed-use tower.

In addition to heating the air inside our homes, heat pump technology can also be used to heat the water that comes out of our taps. A heat pump hot water heater can be 3.5 times more efficient than a traditional electric hot water heat (one that works like a toaster, with an electric heating element), and a crazy seven times more efficient than a gas-burning hot water heater.

One more advantage of heat pumps: because they run on electricity, they can be paired with rooftop solar, so that a home can provide most of its own energy over the course of a year, and with a home battery (or an electric pickup truck), so that your heat pump can run through a power outage.

Induction stoves

Over the last few years, a series of ever-more-alarming studies have shown that gas cookstoves pose serious dangers to health. When gas is burned during cooking, it releases nitrous oxides (NOx), carbon monoxide, and formaldehyde, all of which cause respiratory illnesses like asthma and COPD. Gas stoves create indoor air pollution above legal limits for safe outdoor air; and children living in homes with gas stoves have a 42 percent higher risk of asthma symptoms. Gas stoves leak gas even when they’re turned off, as do the pipes that deliver gas to your home and inside your home; and that uncombusted gas contains 21 different “air toxics” – including several, like Benzene, linked to cancer. 

We don’t need the new technology of induction stoves to avoid all this: ordinary electric stoves have been around forever. But no one loves cooking on a traditional electric stove. Their heating elements take a long time to get hot and a long time to cool down, so they don’t have the sort of instant, precise control that cooks need. No wonder many cooks prefer gas.

Induction stoves solve this problem. They run on electricity, but they don’t work like a traditional electric stove. There’s no heating element. Instead, an electric current runs through an electromagnetic coil underneath the surface of the cooktop, generating a magnetic field. This makes the electrons in your metal pan vibrate, heating the pan. You can set the pan to the precise temperature you want, and you can change it instantly. A pot full of water boils in two minutes. Like heat pumps and EVs, induction stoves are just better, even if you’re not thinking about your own health or the planet’s.

Obstacles and Policy Solutions

If electrified buildings are better, healthier, and nicer to live in and they save money, why aren’t we electrifying them at the rapid pace we need in order to avoid climate disaster?  

Part of the problem is that the world has a lot of buildings. Just in the US, there are 111 million of them, 90% of which are single-family homes – and each one is a little bit different. That means that millions of people need to decide to electrify, find a way to pay the up-front costs, and find a contractor who is willing and able to figure out the right set-up for their particular building.

One part of the problem is that 20 years ago, heat pumps worked poorly in cold climates, and contractors who installed them had to make emergency service calls to angry customers in the middle of winter. So, contractors in cold places stopped installing them – and many still will not, even though the technology in heat pumps has improved radically in recent years, so that they now work well even in extremely cold winters. Contractors matter, because homeowners and building owners usually replace furnaces and water heaters when they break. When it’s cold and they don’t have heat, people don’t have time or inclination to research the best technology. Instead, they turn to a contractor, who installs what they’re already comfortable with and have ready to hand. 

Another part of the problem is that while heat pumps will clearly save money for homes that are currently heated using fuel oil or liquid propane (both of which are common in the Northeast of the United States), it may or may not save money for homes that are hooked up to fossil gas pipes and heated with gas. Whether it will save money for a home heated by gas depends on the set-up of the home, on how much additional work (for instance, new electrical wiring) will be needed in order to install heat pumps, and on the price of gas relative to the price of electricity where the home is located. It also depends whether a home already has central air conditioning. If the price of a heat pump is compared to the price of replacing a gas furnace and a central air conditioner at the same time, then the heat pump is almost sure to save money, because the heat pump gives you two appliances (heating and air-conditioning) in one. 

An obvious way to push through or over these obstacles is with public policies. 

• Governments (local, state, or national) can offer financial incentives to electrify existing buildings, to reduce the upfront costs for building owners. The Inflation Reduction Act (IRA), passed by the Biden administration in 2022, will pay 100% of the cost of electrification for low-income households, 50% for medium-income households, and up to $2000 in a given year for wealthier households. (Rewiring America provides a great calculator to help you figure out your tax credits, and plan a project.)
• The US federal government could pass a bill like the HEATR Act, which offers manufacturers of central air conditioners a financial incentive to spend the extra $400 per unit to make all the air-conditioners they sell into two-way heat pumps, capable of heating and cooling. That way, the 6 million Americans who replace their central air conditioners each year would be getting a heat pump at the same time. 
• Cities and states can alter building codes to encourage or require electrification whenever a furnace or cooktop is replaced. (Right now, many building codes make electrification more difficult and expensive than it needs to be.)  
• Cities and states can prohibit new buildings being built with gas hookups. The city of Berkeley, California passed a law prohibiting gas hookups in new construction in 2019, and at least 77 other US cities have already followed them; so has the state of New York (beginning in 2026). These bans don’t affect existing buildings, but they do respect the principle that when you’re in a hole, the first step is to stop digging. It’s cheaper and better to design a building to be all-electric from the start than to retrofit it later. And experience building all-electric homes helps contractors to become comfortable with heat pumps.

All of these policies would help homeowners and building owners save money. Why aren’t we enacting them everywhere?  There’s a simple answer: they threaten the profits of gas companies and utilities, and so these companies have been fighting policies like this, hard. At the local level, they fund law suits against local gas bans that have been passed, and they create front groups with names like “Coloradans for Energy Access,” complete with fake Facebook profiles, to fight against new ones. They charge customers who switch from gas to electric a $1400 “exit fee.”  They pay actors to show up at City Council meetings pretending to be ordinary citizens. They secretly take over local newspapers, publishing stories that support their interests. And, just since 2020, they have used their money and political power to get legislatures in 20 states to pass state-level “pre-emption” bills that prohibit cities in those states from enacting gas bans.

This means that the challenge of electrifying building is not just technological, social, and financial. It is a political fight – one that needs to be fought at every level of government, from national to very local. (For more, see the section on Politics and Policy under Climate Careers.)

One hopeful development could help to defuse this fight, by turning some of the strongest opponents of electrification into allies. In February 2022, Massachusetts regulators approved a pilot program allowing gas distribution utilities to create six “Geo Micro Districts” (also called “Thermal Energy Networks,” or TENs). The gas utilities, which already have equipment and a workforce skilled in laying pipes beneath city streets, will create networks of underground pipes and deep wells carrying fluid for ground-source heat pumps throughout a neighborhood. This network will play the same role that an individual well for a ground-source heat pump plays for an individual home – except that it will serve a whole neighborhood. The network will bring fluid that has been heated (in winter) or cooled (in summer) by the earth into homes and businesses; and those buildings will be able to install heat pumps to draw heat (or cooling) from that fluid.

Electrifying whole neighborhoods in this way has three, big advantages.

1. Connecting many buildings together is more efficient and less expensive than installing separate ground source heat-pumps beneath individual buildings. 
2. This strategy gives gas utilities – and their skilled workforces – a future in a decarbonized world: they will be able to transition from delivering piped gas to buildings to delivering piped zero-carbon heat (and cooling) to buildings. If this strategy succeeds, it could transform gas distribution utilities from powerful political enemies of electrification into allies.
3. Electrifying whole neighborhoods at a time could help solve a nasty problem that will emerge if we continue to electrify homes one by one: the gas death-spiral. When a gas-heated home pays its utility bill, part of its payment is for the gas it uses, and part goes toward maintaining the network of pipes, compressors, and so on that brings the gas to the home. The cost of maintaining this network is shared by every home and business that uses gas. As more and more buildings electrify and so disconnect from the gas network, the cost of keeping the whole network running safely will be spread among a smaller and smaller pool of remaining gas customers – and so their bills will have to rise. This will incentivize further customers to switch to electricity, leaving a still smaller pool of customers to pay to maintain the network. The problem with a gas death spiral like this is that it worsens inequity: when wealthier people respond to rising gas prices by electrifying their homes, customers who are unable to afford the upfront costs of switching and renters who pay their own utility bills but have no control over how their home is heated will be stuck with higher and higher bills, as more and more of the cost of maintaining the whole gas network falls on their shoulders. 

• When whole blocks are electrified at once using thermal energy networks, the gas pipelines serving those block can be entirely shut off, rather than remaining to serve fewer and fewer customers. And the efficiency of a thermal energy network, together with the savings from no longer having to maintain that part of the gas distribution grid, means that switching can be made affordable and attractive for everyone, including low-income homeowners and landlords. Everyone can come out ahead.

The idea is already catching on. In July, 2022 New York State passed a law creating a pilot program like the one in Massachusetts.

Questions

“Wait! Can’t we decarbonize buildings without electrifying them if gas utilities start providing “Renewable Natural Gas” instead of fossil methane?”

“Renewable Natural Gas” (RNG, also called biomethane or biogas) is methane produced by bacteria digesting organic waste material – whether in landfills, farms, livestock operations, or sewage treatment plants – which would escape into the atmosphere if it were not captured and put to use. When it is captured, it can be low-carbon-equivalent on net, because the warming power of the greenhouse gasses released in the course of capturing, compressing, transporting and combusting it may be balanced out by the warming power of the methane that would have gone straight into the atmosphere if it were not captured. It is a “drop-in” replacement for fossil methane: it can be transported in the same pipes, then used in existing equipment in homes, businesses, and industry. For these reasons, gas utilities promote it heavily as a path to decarbonization. They propose to begin by mixing small a percentage of biomethane into their supply, and then increasing the percentage over time. 

Because methane is such a potent greenhouse gas, capturing and using biomethane where it exists, before it escapes into the atmosphere, is a good idea. And there are some “hard-to-abate” industrial processes where captured biomethane can usefully be put to work. But there is not nearly enough biomethane to replace most of the fossil gas that we use now. 

That’s actually a good thing. Fugitive biomethane leaking from pipes is still a super-potent greenhouse gas, just like fossil methane. Biomethane still produces pollutants like NO_x when it’s burned, just like fossil methane. And low income people and communities of color still live closest to the factories and refineries that would use biomethane, and would still suffer from it disproportionately.

⇒ To learn more about the way in which fossil gas companies are pushing biomethane, even though it is not a realistic or desirable solution for most uses, read this great explainer from David Roberts.

“What if gas utilities start providing renewable hydrogen instead of fossil methane?”

Gas companies propose that they could distribute hydrogen, rather than fossil methane, to homes and businesses, where it could be combusted in furnaces and stoves. Burning hydrogen does not emit carbon dioxide, and hydrogen can be produced in ways that do not emit carbon dioxide either – most notably, by using renewable electricity to electrolyze water. However, hydrogen burns differently from methane, so existing furnaces and stoves would have to be replaced to burn pure hydrogen. And because hydrogen molecules are much smaller than methane molecules, pure hydrogen would both damage and escape from most existing gas pipes. So, gas companies propose to start by mixing hydrogen with the methane that they already deliver in small quantities, thus partially decarbonizing the energy they provide. 

This is another case of gas utilities grasping for a way to stay in business. No more than 5% hydrogen can be mixed with methane in existing pipes without damaging them. Because hydrogen is less dense than methane, this would supply less than 2% of delivered energy content. And producing hydrogen without carbon emissions and then combusting it are both inefficient processes. (See our discussion in the page on transportation.)  These inefficiencies can be worth accepting in some industrial and transportation uses that cannot easily be electrified. But this make no sense at all as a way of heating buildings. Delivering one unit of heat to a home via “green” hydrogen would require five to six times more renewable electricity than delivering it with a heat pump. This would in turn require five to six times more generating capacity, five to six times more resources to produce that capacity, and five to six times more land to site it on.

“What about insulating existing buildings so that they need less energy, and building new construction to hyper-efficient standards, such as Passive House?”

These are important climate solutions!  It’s much easier for a heat pump to keep a well-insulated building warm or cool than a leaky one. And new buildings built to standards like Passive House can be so efficient that they hardly need any HVAC at all.

⇒ Check out:

An efficient building heated by fossil-fuels is better than an inefficient building heated by fossil fuels. But as Saul Griffith says, “we can’t efficiency our way to zero.”  To get to zero, we need to electrify. Efficiency is a great complement to building electrification, but it is not a substitute.

“OK, I get it: we need to electrify buildings. What work needs doing to make that happen?”

We’re glad you asked!

1. Because the challenge of electrifying buildings is, in part, a political challenge, it has political solutions!  State-level policy is key, but individual cities can do a lot. As we describe on the Climate Careers Overview page, the cities of Ithaca, New York and Menlo Park, California have voted to electrify every building they have in the next few years, and they’re working with a smart company, BlocPower, to get the job done. Even if a city isn’t ready to be so ambitious, there’s a lot it can do just by strengthening its local building code. Every city that does this helps to accelerate the snowball rolling down, and makes it easier for the next city to do the same. Organize a campaign to electrify your city – or run for local office, and push for these policies from the inside!
2. Many businesses are finding clever, innovative ways to make it simpler and cheaper for homeowners and building owners to electrify. Individual contractors are building local businesses around electrification. Startups like Goodleap provide low-cost financing specifically designed for sustainability improvements to homes, and a seamless marketplace to purchase and finance those improvements. Sealed will insulate and electrify your home with no upfront cost, and with monthly payments coming only from your energy savings, so that you never have to pay more than you did before the retrofit. And there are many more. Help build a business, or start one, that removes obstacles to electrification.
3. If you own a home (or have family members who do), electrify it!  Climate change is a systems problem, and most of our individual consumer choices have little impact on it. But as Griffith points out in chapter 9 of Electrify, choices regarding our homes and our vehicles are different. These are our personal infrastructure, which we use every day. Together, they account for more than 40% of Americans’ emissions. (If we include offices and company cars, the number goes to 60%.)  So, this is one place where individual choices really can make a meaningful difference. Everyone’s decisions matter, because the only way to decarbonize buildings is one building at a time. And our decisions are contagious: when people visit friends’ electrified home, and realize it’s more comfortable and more economical, they want one themselves.
4. Push your workplace, school, or college to electrify. It will save money, make your workplace more comfortable, and help us preserve a livable planet. Rewiring America has a great guide, with everything you need to convince your school to electrify. And pressure from students, faculty and other employees, and alumnae has helped to convince many colleges to take the plunge.

Further Resources

• This Volts podcast interview with Panama Bartholomy provides a great overview of the whole space of building decarbonization
• The Building Decarbonization Initiative is a non-profit started by Bartholomy. The website is full of great resources, from guides for homeowners to policy papers.
• Rewiring America is a non-profit started by Saul Griffith, the author of Electrify. The website has terrific resources for homeowners (including a step-by-step guide for homeowners who want to electrify, complete with information about tax credits). It also has guides for renters, for local governments and school districts, and for business leaders who want to drives progress on electrification.
• This Canary Media story explains district thermal networks
• This Volts Podcast describes an ingenious business model for commercial buildings, “efficiency as a service”
• This US Department of Energy Report, Decarbonizing the US Economy by 2050: A National Blueprint for the Buildings Sector, provides a comprehensive strategy for decarbonizing US buildings over the next 25 years.
• The International Energy Agency’s Future of Heat Pumps report explores the policy and other measures that can overcome existing barriers and accelerate heat pump deployment around the world.

Here are some startups working to decarbonize buildings, along with some articles and podcasts about them in the right-hand column. Use the scroll bar within the embedded window to see more: