Heat pumps are cool. They’ll get cooler when new refrigerant regulations come into effect.
Today’s post was co-authored with Duncan Callaway.
Gee, it’s so hot. We have been experiencing record heat in California.our house is one of 30% California home without air conditioning. and oYour stove is getting older. If we replace our furnace with a heat pump, we can get efficient heating and efficient cooling one. We will do our part to drive decarbonisation through building electrification. So we were curious about heat pumps.
Joe Biden is excited about heat pumps. He recently invoked the Defense Production Act to boost domestic production, and the Reducing Inflation Act includes generous heat pump tax credits and rebates. Governor Gavin was also enthusiastic.He’s offering rebates to California families to help him meet his goal of Six million additional residential heat pumps will be added by 2030.
Some A recent study UC Davis researchers have found that for homes installing an air conditioner for the first time, or those that need to replace an old air conditioner with a new unit, turning the air conditioner into a heat pump and replacing the furnace makes climate sense. We’re pretty sure we’ll have a heat pump in the future. For us, the question is not whether to get a heat pump… but when?
If we invest in a heat pump today, we can shift our home heating business from natural gas to California’s greener grid every year. However, the refrigerants used in today’s heat pumps can have serious climate shocks. Tomorrow’s refrigerants will be more climate-friendly thanks to some amazing efforts to tackle this problem.
We’re energy nerds and we spent a Saturday night working on this heat pump climate impact math. While we are convinced that building electrification needs to accelerate across the country, we are now also convinced that we should wait a few years before joining the revolution. For us, these calculations also underscore the critical role of regulations that should soon shrink the carbon footprint of refrigerants used in heat pumps and air conditioners.
*If you’re curious about how we got the numbers in this blog post, go to the end to see the unstable list of assumptions, calibrations and equations.*
Refrigerant GWP is BFD
Heat pumps use refrigerant to efficiently bring warmth into your home in winter and remove heat from your home in summer. Today’s residential heat pumps use R-410A, which has a 100-year Global Warming Potential (or GWP) of 2090. English translation: One ton of R-410A refrigerant absorbs as much heat in the atmosphere as 2090 tons of carbon dioxide. oops.
Heat pumps should not leak refrigerant. But they do. Leak rate estimates vary. The UC Davis study we mentioned above assumed a 6% annual leak rate when the heat pump was removed and the refrigerant was recycled, and 25% at the end of its useful life.this Well-documented calculator from E3 Assume that the leak rate is about the same every year, but the end-of-life leak rate is 80%.
The heat pump recommended for our home would use about 9 pounds of R-410A. Using the leak rate assumptions of the Davis study, our hypothetical system would release less than 10 metric tons of total CO2 equivalent over the 15-year life of the heat pump (see calculations for details). To put this into perspective, the EPA estimates that a typical gasoline-fueled vehicle emits about 4.6 metric tons of carbon dioxide per year.
As we’ll show later, these heat pump refrigerant emissions can be offset over the life of the heat pump by not burning natural gas (and releasing the associated carbon dioxide).So IIf you need to install new cooling equipment today, you might as well install an efficient heat pump and get rid of your furnace at the same time. But if you can put it off a few years, upcoming regulatory changes will make the climate math for heat pumps better.
Over the past decade, a firm alliance environmental groups, Regulatory Authorityand a key industry trade association There has been a tireless effort to get super greenhouse gas refrigerants out of air conditioners and heat pumps. They are succeeding. The United States has now committed to phasing out the use of these refrigerants. In California, CARB will limit the GWP of refrigerants used in new residential air conditioners and heat pumps to 750 (or lower) by 2025.
We called some HVAC folks and they explained that heat pumps using a refrigerant called R-32 could become the new low GWP standard. But these heat pumps are not yet on the market, and the building codes that allow us to install have not been updated. So we need to wait for the new rules and norms to come into force before 2025. And, in case you’re wondering, we can’t install today, and we can’t change the refrigerant tomorrow. We understand that these new refrigerants require new heat pump technology.
If we conservatively assume that current leakage rates will not improve between now and 2025, we estimate that a heat pump purchased in 2025 will have a refrigerant carbon footprint of just over 2 metric tons over its 15-year life. That’s a big difference from the nearly 10 metric tons emitted by today’s heat pumps.
So far, we’ve considered the climate benefits of waiting. But there are also some delayed climate costs. Based on data from our home (see below), we estimate that by switching our natural gas furnaces to more efficient heat pumps, we could save about 1 metric ton per year in energy use-related emissions. These annual reductions are more than enough to offset the leakage emissions from today’s heat pumps Over 15 years of appliance life. But the climate benefits of waiting until 2025 easily outweigh the climate costs of delaying. This makes us tend to put off this home improvement project until we can get access to more eco-friendly items.
Consideration, Warning, Conclusion.
We’re not saying heat pumps are bad for the climate! If your air conditioner breaks and you need to replace it today, the climate will benefit if you opt for a heat pump and replace your furnace.here Californiait makes sense to use heat pumps for new buildings and homes where people now need cooling to handle today’s heat.
We suggest that for those households (like us) who have some flexibility in purchasing heat pumps, the refrigerant-related climate benefits of waiting may outweigh the energy-related climate costs of delay. Of course, numbers will vary based on the climate you live in, the size of your home, and the fuel mixture used to generate electricity. If you want to DIY your own heat pump climate impact calculation, see the nerdy details below.
Finally, following these calculations, we gain new insight into the high-risk importance of phasing out high-GWP refrigerants. EPA phase-out regulations now finalized. Further efforts are underway. California recently passed a law (SB 1206) to support enhanced refrigerant recovery and reuse. AB 209 invest $40 million to accelerate adoption of ultra-low GWP refrigerants. When we roll out incentives to get people to heat pumps, these moves (and more!) will be needed to keep the refrigerant at work and not in the atmosphere.
Follow Energy Institute blog posts, research and events on Twitter @energyathaas.
Suggested Citation: Meredith Fowlie and Duncan Callaway. “Tackling Climate Change with Heat Pumps”. Energy Institute Blog, UC Berkeley, September 6, 2022, https://energyathaas.wordpress.com/2022/09/06/fighting-climate-change-with-heat-pumps/
Assumptions, equations, calculations.
Furnace can use emissions: We start by downloading our gas consumption data. We did an estimate of the average usage over the summer to estimate the gas consumed for cooking (we have an electric water heater). Subtracting this from winter consumption, we estimate that an average of 218 kcal of natural gas is required per year for space heating.This equates to direct emissions of 1.3 metric tons of carbon dioxide per year, using Figures published by PG&E carbon dioxide per kilocalorie.Then we assume a 3% leak rate In the natural gas supply chain, Methane has a GWP of 30and higher calorific value 22,446 Btu/lb Estimated 0.4 metric tons of CO2-equivalent emissions due to leakage. This emits a total of 1.7 metric tons of CO2e due to our gas furnace running for one year.
Heat pump energy use emissions: Assuming our furnace is 80% efficient and any heat pump we might buy has a COP of 3.3, we will be using 1,548 kWh of electricity per year to heat with the heat pump. E3 estimate The average marginal operating emissions intensity of California’s electricity system will average 0.39 metric tons of carbon dioxide per megawatt-hour over the next three years. This is equivalent to the direct emission of 0.6 metric tons of CO2 per year for the electricity use of our future heat pumps. To calculate indirect emissions from methane leakage from electricity generation, we assumed that all marginal electricity emissions in California come from natural gas. Assuming an average efficiency of 50% for gas-fired power plants, 1,548 kWh of electricity would require approximately 105 kcal of natural gas input to the generator. Using the higher calorific value, leak rate, and methane GWP described above, the CO2 emissions from gas leaks from our electricity consumption are approximately 0.2 metric tons. This corresponds to an emission of 0.8 metric tons of CO2e due to operating the hypothetical heat pump for one year.
A punchline for energy use-related emissions: Switching to heat pumps today will reduce energy-related carbon dioxide emissions by approximately 0.9 metric tons per year over the next few years. (If you consider the gas leak to be non-trivial, that’s a saving of 0.7 metric tons per year.)
refrigerant discharge: Our family has an HVAC company. They recommend a system that can deliver 36,000 BTU per hour (also known as a 3 “ton” system).many websites (such as here and here) indicates that air conditioners and heat pumps should be charged with 2-4 pounds of refrigerant per ton. We used a central estimate (3 pounds per ton) to estimate that our home’s heat pump requires 9 pounds of refrigerant.
To estimate how much leakage will occur over the life of the heat pump, we started with the same leak rate from the Davis study and calculated that 112.5% of the refrigerant charge would leak over the 15-year life of the heat pump. (This obviously assumes that the system will be charged at least once in its lifetime, since it leaks more than it can hold.) For R-410a with a GWP of 2090, that equates to 9.6 metric tons of carbon dioxide emissions.We found some estimates (e.g. this 1) R-32 system can use 20-40% less refrigerant than R-410a. Therefore, we assume that the R-32 heat pump will charge 30% less than the heat pump using the R-410a, which equates to 6.3 pounds for our hypothetical system.Using the same percent leak rate as R-410a, and a GWP of 675 for R-32, the calculation is 2.2 metric tons of carbon dioxide equivalent emissions from the R-32 system.
Quotations for refrigerant leak emissions: Switching to a heat pump today, rather than waiting for a greener one to come online, would increase refrigerant-related CO2 emissions by 7.4 metric tons CO2-equivalent throughout the life cycle of the heat pump.