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A study published in Energy Policy by researchers at the University of California, Davis, shows that a typical American home could reduce its heating-related climate pollution by 45 percent by replacing its gas furnace with an efficient all-electric heat pump. 72%.This is the case in every region of the country starting today.
The study’s proponent, the NRDC, asked UC Davis to investigate the issue for several reasons.We often hear the concern that the CO2 emissions from powering heat pumps today are making them so dirty that we should wait to electrify – or replace appliances that run on fossil fuels in exchange for efficient electric models that can be powered by clean energy – until the grid gets cleaner.Other times, we’ve heard that turning on electricity too early can exacerbate the effects of hydrofluorocarbon (HFC) refrigerants, which can cause climate change when leaking from appliances.
The new findings address both questions — plus the switch’s effect on fugitive methane emissions — and confirm that the time for action is now.In short, here are the results.
Compared to the CO2 emissions from burning the gas in a furnace, the biggest factor in the findings was the CO2 emissions from the electricity needed to run the heat pump.The study used the EnergyPlus model to calculate the annual energy use of an average single-family home (including the years 2006 and 2018, with no significant change in score results).It compares high-efficiency gas furnaces to high-efficiency heat pumps (up to 10 HSPF, depending on size), the type of equipment we need to deploy to get rid of fossil fuels and maximize energy savings at the same time.
To convert energy use into emissions, the study looked at the power grid in terms of how it is expected to grow to meet our electrification needs, based on hourly data from the National Renewable Energy Laboratory’s (NREL) new Cambium dataset.This is known as the “long-term marginal emissions” rate and is a better way to look at future emissions than assessing current power plants.This approach argues that when we power heating, cars, etc., some new power plants need to be built to serve new electrical loads.NREL’s Cambium data takes into account current federal, state, and local energy policies and the economics of natural gas, solar, wind, storage, and other power generation sources to estimate which new generations are most likely to serve new hourly loads That year.The emission intensity of energy use is as follows.
Many states have adopted policies to increasingly use clean energy to power the grid.Those haven’t seen a similar shift, thanks to rapidly falling prices for wind, solar and energy storage.Taken together, this means that the average carbon footprint of new energy sources is already much lower than today’s gas-fired power plants, and continues to decline rapidly.
For this reason, the study found that heat pumps have excellent lifecycle climate performance.Here’s how it works: The average heat pump installed this year will last about 15 years, or until the 2030s.The grid will be cleaner between now and then – President Biden’s plan is to have the grid 100% clean by 2035, although the authors use Cambium’s “low renewable energy cost” scenario by 2050 Contains only 70% clean energy.Either way, as the grid grows with clean energy resources, heat pump emissions will drop rapidly over their lifetime.For these reasons, heat pumps are the climate-smart option for installations today.
There is similarly good news for HFC refrigerants.First, a quick primer: HFCs are super-potent greenhouse gases—thousands of times stronger by weight than carbon dioxide—used in air conditioners and heat pumps to help produce cooling and heating.
Due to the environmental impact of HFCs, under the American Innovation and Manufacturing (AIM) Act, the United States is in the process of phasing out 85% of its economy-wide HFCs over the next 15 years.Under the plan, heat pump manufacturers will soon switch to models with climate-friendly refrigerant alternatives.As HFCs become more scarce, the amount of refrigerant emissions that can be avoided is also expected to decrease, so the cost of waste is too high.NRDC also advocates for policies to increase the recovery rate of end-of-life refrigerants and facilitate leak repair.As with the overall study, these HFC refrigerant leakage forecasts are specific to single-split heat pump units installed in homes and do not address potential issues for other system types, such as large site-built residential and commercial systems that could have a significantly higher impact. leak rate.
The study assumes that heat pumps will continue to use current HFC refrigerants for the next few years, before transitioning to climate-friendly refrigerants by mid-century.Before and after this transition, the climate benefits of heating electrification far outweigh any potential incremental risks from refrigerants.Here’s why: Most American homes already have some type of air conditioner, which itself uses HFC refrigerant, connected to the stove.In these cases, replacing the furnace with a heat pump is just “responsible” for adding the extra refrigerant needed.The authors found that this is not a lot.
In conclusion, while we need to get rid of today’s HFC refrigerants quickly, it should not hinder the unimpeded push towards electrification of heat pumps.
In the end, a large part of the benefits of switching to a heat pump comes from reducing fugitive methane emissions associated with combustion gases in household furnaces.Methane leaks at every stage of the supply chain, from extraction wells to processing, distribution, metering, household plumbing, and the burners themselves.The study found that when methane’s impact on the climate over more than 20 years is considered, the methane that leaks into the atmosphere has almost as much impact on the climate as the methane that is burned for heating.This metric is clearly in favor of the heat pump, even considering that for a while some of the gas would leak on the way to the power plant to power the heat pump.This effect diminishes as the share of renewable energy grows rapidly.
Taken together, these numbers clearly show that it’s time to energize our heat.Overall, the study’s population-weighted average of 99 U.S. cities showed a 53-67% reduction in HFC and methane using 20-year global warming potential (GWP) and a 44-60% reduction using 100-year GWP​​ %, and a 38-53% reduction in CO2 alone (ie results excluding HFC and methane, although we do not recommend this).
As you might expect, emissions reductions are best in the Pacific and Northeast regions, which already have fairly clean grids.But the results were remarkably consistent across regions, and using 20-year GWP values, none of the country’s major climatic regions showed a reduction of less than about 45 percent.Equipment installed today in some regions is starting to drop by as much as 72 percent.
Now is the time for policymakers in every state and Washington, D.C. to start the news all over the place to deploy heat pumps into our homes and buildings.A good start would be the heat pump incentives in the climate package of the Build Back Better Act that Congress should pass.Consumers looking for a new air conditioning or heating system should opt for a heat pump if they can.The best time is when a new central air conditioner is needed, as a heat pump that provides both cooling and heating is available for a fraction of the cost.This is a great deal for a brand new heating system that will save you money and your child’s future.Replacing a burnt out stove is also a great occasion.
Heat pump manufacturers should prepare for a full transition to heat pumps as soon as possible, especially models using climate-friendly refrigerants.This is also a good time for manufacturers to improve the energy efficiency of their models and limit the additional refrigerant charge required for their heat pump models.
Of course, for this study’s predictions to come true, we must continue to make rapid progress on other climate goals: choosing efficient appliances, greening the grid, tightening methane leaks, and reducing the climate impact of HFC refrigerants.If we are to succeed in making the future climate impact of home heating as close to zero as possible, we must address both of these issues.
This winter, take a moment to think about where the heat that keeps you warm comes from.Let’s all find a better way.
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