This story was first published canary media.
You might think heat pumps are an attractive climate change solution (they are) and what you yourself can adopt (have a lot). But you're probably wondering how much of a difference it really is if the dirty power grid is supplying the electricity you're using to power it, i.e. the grid from which at least some of your electricity is generated. You've probably held off on buying one because you wondered if it existed. Fossil gas, coal, or oil.
That's certainly true for most households in the United States. Improve, it's still far from clean. In 2023, renewable energy sources will provide just 21 percent of U.S. electricity generation, with carbon-free nuclear energy accounting for 19 percent.the other one is 60 percent Most of the electricity was obtained by burning fossil fuels.
So can electric heat pumps really reduce emissions when run on dirty grid electricity?
The answer is clearly yes. Even if you have a carbon-rich diet, heat pumps reduce emissions by tons per year compared to other heating systems.
of latest research To understand this point clearly, Joule The National Renewable Energy Laboratory announced this last month. The research team modeled the entire U.S. housing stock and found that switching to heat pump heaters/air conditioners would reduce emissions in all 48 contiguous states over the 16-year expected lifespan of appliances. discovered.
In fact, heat pumps reduce carbon pollution, even if the process of cleaning up the U.S. power grid is slower than experts expected. The NREL team used his six different future scenarios for the grid, from aggressive scenarios. decarbonization (95% carbon-free electricity by 2035) to sluggish (only 50% carbon-free electricity by 2035 if renewable energy costs are higher than current trajectory projections). They found that depending on the scenario and efficiency level, heat pumps can reduce a household's annual energy emissions by an average of 36% to 64%, or 2.5 to 4.4 tonnes of CO.2 Equivalent to one year per housing unit.
That's an astonishing amount of emissions.For context, preventing 2.5 tons of CO2 emissions is equivalent to Not burning 2,800 pounds of coal. Or maybe you haven't driven for six months.or switch For vegan meals For 14 months. And at the upper end of the study range, the CO reaches 4.4 tons.2 This is roughly equivalent to the emissions of a round-trip ticket from New York City to Tokyo (4.6 tons).
Eric Wilson, a senior research engineer at NREL and the study's lead author, told me: False logic. “It’s better to switch now than later. You don’t have to keep using your gas furnace or boiler for another 20 years.”
Studies show that states like Maine, where winters are cold and heating appliances run on fuel oil, tend to have higher emissions reductions. (Maine seems to be one step ahead of researchers, as heat pumps have proven so popular there that the state has already Achieved heat pump introduction target Two years earlier than planned. )
Therefore, a dirty grid does not offset the climate benefits of heat pumps. But heat pumps, like standard air conditioners, can produce emissions due to leakage of refrigerant, the chemical that allows the equipment to move heat around.Even though it has been gradual reductionHVAC standard refrigerant R-410A is 2,088 times Greenhouse gas more powerful than CO2Therefore, even a small leak can have a big impact.
However, the NREL team found that the additional emissions from heat pump refrigerant leaks have little impact when considering the emissions that heat pumps avoid. Typical leak rates for R-410A result in an average increase in emissions of only 0.07 tons of CO2 This equates to 2.5 tonnes per year, with an overall savings of just 3%, Wilson said.
a 2023 analysis Information from climate think tank RMI further supports the climate change legitimacy of heat pumps. Across the lower 48 states, RMI has found that replacing gas furnaces with efficient heat pumps not only reduces emissions cumulatively over the lifetime of the equipment, but also reduces emissions in the first year the equipment is installed. was found to be reduced. RMI estimated that emissions prevented in his first year were 13-72% compared to gas furnace emissions, depending on the state. (Canary Media is an independent affiliate of his RMI.)
Both the RMI and NREL studies focused on air source heat pumps. Air source heat pumps draw heat from the outdoor air in cold weather and can be three to four times more efficient than gas furnaces. But ground source heat pumps can be more than five times more efficient than gas furnaces, allowing for even greater greenhouse gas reductions, according to RMI.
How much can you save by switching to a heat pump? your What is your home's carbon footprint? NREL provides the following rough estimates: interactive dashboard. The (State) tab allows you to filter by state, building type, and heating fuel. For example, based on a moderate grid decarbonization scenario in my state of Colorado, a single-family home that replaces a gas furnace with a heat pump could reduce its CO emissions by a whopping 6 tons.2.
You can also get a quote from Rewiring America's. personal electrification plannerthis can be done using more specific information about your home, or asking your energy auditor, Whole house decarbonization company If emissions reductions can be calculated as part of home energy audit.
The final lesson Wilson shared is that if every American household using gas, oil, or inefficient electric resistance heating replaced it with heat pump heating right now, the entire U.S. economy would reduce its emissions by 5. It would be reduced by 9% to 9%. That's why heat pumps are so powerful as a decarbonization tool.